implementing neuroscience principles

8/13/2019 Implementing Neuroscience Principles

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CH PTER ONTENT UTLINEBasic Neurological Principles that The Affective SystemsSupp or t Per formance Emotional SystemT he Sensory Systems Motivational SystemTh e M otor Systems SummaryIn teract ion Am ong S ensor imotorSystems to Support PerformanceTh e Cognitive Systems

This chapter reviews the basic systems and functions of the central nervous sys-tem . After providin g overviews of each system the chap ter also provides m etho dsfor interpreting t he m eaning of behaviors from a neuroscience poi nt of view.

Autogenic hcili ta tionAutogenic inhibitionBalance of pow erCentrifugal controlConvergenceDivergencePlasticityKelease ph nom nonSuppressionExcitationInhibitionIntersensory integration

Com pensa tory ac tion of the C N SCorporal potentialityTopographicTonotopicSomatotopicHabi tua t ionSensitizationPoo r registrationSensitivity to stimuliSensation seekingSensation avoidingHom onymous he mia nop ia


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Neuroscience Principlesto Support Habilitationand RecoveryWinnie l>ui~n hD OTR FAOTA

O JECTIVESThe i y m a t i o ~ ~n this chaptcr is iutended to help the ven de~ c1. apprec iate the imp or tance o f va r ious brain f imc t ions in th e pe r formance o f

life tasks2 . ident i fp the basic neurologica l mech anisms which sup po rt performan ce3. ciescribe thc similarities a n d differences a m on g s ys t e ~ n s i t h in t h e c e nt ra l

IIer \~O lIS YStClll4. unde rs tand the ro le s of a tt cn t iona l mot iva t iona l a n d emotional sys tems ins u p p o r t o f p e r fo r m a n ce5. r ecognize examples of r elea se p l i e nom cn~ lw i t hi n t he C N S6 ident i@ range of contextua lly rc lcvant in te rvent ions to sup por t per for-

mance in persons with bmin involvement in the ir disabi l i ty7. in te rpre t the ~ i ica nin g f behavior s f rom a neurosc ience poin t o f v iew as a

c on t r i bu t ing f ac t o r in in t e r ve n t ion p l ~ n n i n g .


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discuss descend ing inhibition (i.e., higher centers h avingfect on lower cente rs), the CN S is rich w ith interneuron

which con tributes to organization and integration

eedback and eedforward Mecha nismsFeedbac k is the CNS s ability to sen d information back

the future . Nohack Dernerest ( 198 I describe two gen-

signal to the motor nerve, thus allowing a pcrson to relaxop the movement. T his inhibition, however,

rs only if the local circuit neuron information is stronger

either easier or more difiicult to activate the neu rons.Feedforward circuits exert influence in a forward direc-

Intersensory IntegrationIntersensory integration is a critical feature of the CNS.

PlasticityPlastic ity is the CNS s ability to ad apt structura

functionally in response to environmental demPreviously, neuroscientists believed that plasticity wasevident during the prenatal stage and childhood;researchers have found that there are various types of nal and external environmental alterations that suppinhibit the man ifestations of plasticity (L und , 1978). individuals participate in interventions that require functional patterns of m oveme nt, they receive organizeterns of sensory feedback that may alter the internal enment, creating opportunities for axon reorganization, asynaptic activity, or dendritic branching, just as enenvironments support these actions during the developmperiods (Bac h-y-Rita, 1980; Moore, 1980). Such finchallenge innovative rehabilitation practice.Compensatory ction of the CNS

Parts of the CNS are interdependent (Moore, When da mage occurs to on e or more portions of the sythe interdependency relationships are disrupted; the resobservable behaviors and performance are hypothesizbe compensating for the loss of information from onemembers. This compensatory model suggests that thecenters do not function on their own to initiate actiowork as part of a network in the CNS to enable a partaction. When data are not available to the system becadamage, the network is disrupted, making it difficultparticular action to occur. Destructive behavior is the of an incomplete and compensating CNS.Summary

The principles of centrifugal control, balance of etion and inhibition, plasticity, and compensatory actiobasic and must be used to design interventions that suoccupational performance. Interventions that conflictthese basic principles compromise the person benabling them to profit from the therapeutic experienc

The olfactory (smell) and gustatory (taste) systemprimitive, chemically-based sensory systems signalinCN S about odo rs and tastes. The somatosensory, proprtive and vestibular systems enable an individual to dean accurate map of self and how one interacts with theronment. Finally, the visual and auditory sy stems are resible for mapping environmental variables so that interwith the environment can he accurate and reliable.


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Although each sensory system is unique, there are some

Input tnechrrnisms. Each sensory system is responsiblefor bringing information from the environm ent to the ner-vous system for processing.Processing levels. Each sensory system processes its ownspecial brand of information at a variety of central ner-vous system levels including the receptor site, spinalcord, brain stem, thalamus (except for olfactory), andhigher cortical centers.Mul t i d im ens io t~ u l t l fi rn~ t rt i o tr .The sensation from eachsensory system is complex and m ultidimensional.Purposes f i r processii lg infortntrt iotr. Each sensory sys-tem processes information for two primary purposes: a )to identify stimuli in the environment, making the CNSaware of these stimuli, determining w hich require atten-tion and which are potentially harmful (i.e., arousal oralerting mechanisms) and b) gathering information toconstruct maps of self and environment to bc used by theCNS for organization and planning (i.e., discriminationor mapping).When the CNS is functioning normally, the arousallalert-

a balance of power. This allows the indi-discrimination and m apping under m ost conditions,

ent of environmental stimu li so that

The components of arousallattention and discriminalionlin each sensory system section. As

s, Tables 8- 1and 8- 3 summarize key information that can be used thcr-

Table 8 2 uses the sam e descriptor words and organizing

can be a therapeutic input if a provider needs to increaalertness in a person who is lethargic; the additional arousalerting input could establish a more optimal biobehaviostate for engaging in a functional task. In a later section will consider ways to use these sensory stimuli in relationthe arousal and attentional mechanisms.

Table 8-3 contains examples of observable behaviowhich might indicate difficulties with sensory processiduring daily life tasks. Information from this table could used to construct a referral or observational checklist interdisciplinary team members and assist team memb(including family m embers) in learning how to consider impact of sensory processing on performance.The hemical Senses

Th e gustatory system is responsible for our sense of tasEarly in evolution, the differentiation between the gustatoand olfactory systems was minor because primitive orgaisms lived in the sea. When they moved to land, these tsystem s differentiated to serve the organism in very differways. The gustatory system became the final checking stem for food that was to enter the body. whereas the olfacry system became the chemical sense that could determthe location or direction of stimuli (e.g., food or predatofrom a distance. The olfactory system becam e important mapping the environment for survival (Coren, Porac,Ward, 1984) . From a neuroanatomical standp oint, sensessmell and taste travel by very different routes to inform cerebral cortex about environmental events.

The ustatory SystemTaste is determined by an items solubility. intensity, a

amount. There is general agreement that taste can be labelwith la nguag e: sweet. salty, sour, and bitter (Co ren, Porac,Ward. 198 4). Tastes are discriminated both by the typesmolecules found and by the way they are broken do wn by chem icals within the sy stem . Taste buds are the receporgans fo r the gustatory system. As many as 10,000 tabuds are available to young people; this amount decreaduring the aging process.Gustatory information travels from the sensory receptin the tongue to the brain stem where the informationrelayed to the thalamus. The thalamus sends informationthe cortical taste area in the sensory homunculus or the paetal lobe and enables us not only to have an accurate mapthe tongue but also to allow conscious sensation of ta(Heimer, 1983 ). Beca use taste is part of the cranial nerve nwork. its functions are jeopard ized by brain stem traumAdditionally, gustatory information reaches both the hythalamus and the cortical taste area in the inferior frongyrus. Degenerative neurological diseases that affect th


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m to ingest food (Bellin gham , Wayne,Barone, 1979).The characteristic taste patterns of the tongue have beenn is important from a neuroscience standpoin t, from a

individual s response to taste are very

of people as being immune

eine and those who do not (Blakeslee Salm on, 1935;ren, Porac. Ward, 1984; Hall. Bartoshu k, Cai n,

1975). From testing various substances, researchers

Because of the deterioration process with aging, elderlyan (1 98 0) fou nd that salting food is in part a per-

s attem pt to reach that person s specific threshold for10 seco nds after the stimulus. so a slower eat-

lfactory SenseThe olfactory system responds to odors in the environ-

The olfactory system is a very sensitive system , even more

le to discover basic categories of sm ell. The system is somany types of odors,

Humans tend to underrate the role and effects of the

arouse people in semi-comatose states points out the poful role of olfactory input.

Clinicians must remain aware of the olfactory sesystem in the planning and provision of services. Beindividuals em it specific odors, persons may recognizetherapist not only from visual, auditory, and somatosecues. but also from olfa ctory cues. This factor may contrto disorientation and agitation when substitutions oAdditionally, therapists must be very careful about the tions of odors such as shampoos, perfumes and laudetergents. Although these factors go unnoticed by themally functioning nervous system, a vulnerable systemreact in unpredictable ways. Therapists must considepossibilities when unusual behaviors present themselvobservable behavior provides a window to CNS activity

Olfactory input is also important in the environmwhere per sons are served. The sterile environmen t of thpital provides a type of olfactory sensory depriv(M oor e, 198 0). In the familiar home environment. the tory system can contribute to orientation by familiar od

Persons who have difficulty with the olfactory soften begin to comp lain ab out the taste of food s. Even ththe smell of fo od does not con tribute directly to its tasteple seem to associate the smell of food with the Bec ause both taste and smell relate to individuals fooderences, therapists should be curious regarding intertions of food conlplaints.

omatosensory ystemThe somatosensory system responds to stimuli fro

skin surface. The unique placement of these receptors swhere the body ends and where the world begins. The bined input from various somatosensory receptors fomultidimensional picture of skin stimulation.

Receptive fields are the loc ation on the surfac e of ththat is innervated by one neuron; they contribute to niurnensional maps. Accurate somatosensory percerequires not only that the receptive fields function acculy, but that they function in concert with each oReceptive fields overlap a great deal on the head. handsarms (Figure 8-1 ), whereas they overlap very little oback (Figure 8-2). This is functionally significant behuman beings identify the exact location of the touch exence on body surfaces that have overlapping receptive fbecause the various neurons from several receptive fieldshare that location report information to the brain simuously, but can only identify the general area being touchthe hack. Multiple input from various sources enablebrain to narrow the possible locations until it can identifone spot on the surface of the skin that is shared by all activated neurons.


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T A B L E 8 1Arousal/Alerting and Discrimination/Mapping Descriptors o the Sensory System

ArousaYAlerting DescriptorsUnpredictable:The task is unfamiliar: the childcannot anticipate the sensory experiences thatwill occur in the task.Light touch: Gentle tapping on skin; tickling(e.g., loose clothing making contact with skin).Pain: Brisk pinching; contact with sharp objects;skin pressed in small surface (e.g., when skin iscaught between chair arm and seat).Temperature: Hot or cold stimuli (e.g.. iceddrinks, hot foods. cold hands, cold metal chairs).Variable: Changing characteristics during thetask (e.g., putting clothing on requires acombination of tactile experiences).Short duration stimuli: Tapping, touchingbriefly (e.g., splashing water).Small body surface contact: Small bodysurfaces, as when using only fingertips to touchsomething.

Predictable: Sensory pattern in the task isroutine for the child, such as diaper changing-the child knows what is occurring and what willcome next.Touch pressure: Firm contact on skin (e.g.,hugging, patting, grasping). Occurs both whentouching objects or persons, or when they touchyou.Long duration stimuli: Holding, grasping(e.g., carrying a child in your arms).Large body surface contact: Large bodysurfaces include holding, hugging; alsoincludes holding a cup with the entirepalmar surface of hand.

Head position change: The child s head orienta-tion is altered (e.g.. pulling the child up from lyingon the back to sitting).Speed change: Movements change velocity (e.g..the teacher stops to talk to another teacher when

Linear head movement: Head moving in astraight line (e.g., bouncing up and down. goingdown the hall in a wheelchair).Repetitive head movement:Movements that repeat in a simple

pushing the child to the bathroom in his wheelchair). sequence (e.g., rocking in a rocker).Direction change: Movements change planes.such as bending down to pick something up fromthe floor while carrying the child down the hall.Rotary head movement: Head moving in an arc(e.g., spinning In a circle, turning head side to side).Quick stretch: Movements that pull on the Sustained tension: Steady, constant action onmuscles (e.g., briskly tapping on a muscle belly). the muscles pressing or holding on the muscle

(e.g., using heavy objects during play).Shifting muscle tension: Activities that demandconstant change in the muscles (e.g.. walking,lifting, and moving objects).

High intensity: Visual stimulus is bright (e.g., Low intensity: Visual stimulus is subdued ( e g ,looking out the window on a bright day). finding objects in the dark closet).High contrast: A lot of difference between the High similarity: Small differences betweenvisual stimulus and its surrounding environment visual stimulus and its surrounding environmen(e.g., cranberry juice in a white cup). (e.g., oatmeal in a beige bowl).Variable: Changing characteristics during the Competitive:The background is interesting ortask (e.g., a TV program is a variable visual busy (e.g., the junk drawer, a bulletin board).stimulus).


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T A B L E 8 1 ( c o n t i n u e d )Arousal Alerting and Discrimination Mapping Descriptors of the Sensory System

Sensory System ArousallAlerting Descriptors DiscriminationiMapping DescriptorsAuditory Variable: Changing characteristics during the Rhythmic: Sounds repeat in a simple sequen-

task (e.g., a person's voice with intonation). celbeat (e.g., humm ing: singing nursery so ngsHigh intensity: The auditory stimulus is loud Constant: Th e stimulu s is always present (e.g(e.g., siren, high volum e radio). a fan noise).Competitive: Th e environment has a variety o

recurring sounds (e .g., the classroo m, a party).Noncompetitive: The environment i s qu ie t ( ethe bedroom when all is ready for bedtime).Low intensity: The auditory stimulus issubdued (e.g., whispering).

Olfactory1 Strong intensity: Th e tastelsmell has distinct Mild intensity: The tastelsmell has nondistincgustatory qualities (e.g., spinach ). or familiar qualities (e.g., cream of whea t).

' :Arousalialerting stirnuli tend to gene rate noticing behaviors. The individual's attention is at least momentarily drawn toward the stimulus (commol y disruptin g ongoing behavior). These stirnuli enah le the nervous system to orient to stimuli that may require a protective re\ponse. In some situatio;In a rou \ in g st im u lu ., c a n b e c om e p a r t o f a fu n ct io na l b e h av io r p a tt ern ( e . ~hen the arousing som atosenso ry input from putting nn the shirt becompredictable. a discrirninatinglmapping characteristic).*:Wiscr i~ninatory /~nappingt imuli are those that enable the individual to gather information that can be uscd to supp ort and genemte functional behaiors. The information yields spatial and temporal qualities of body and environment (th c content of the ma ps) , which can be used to create purpo\efuInovement. These stimuli ;Ire more organizing f or the nervous syste m.From Dunn , W. (1991 . The senwrimotor systems: A framew ork for as\essrncnt and intervention. In P. Ore lovc D. Sohsey (Eds.), Educ.utir~,y htlrcw ~v i th i i~ r l t i p l rli.srrhilitirs: A t rr~~vrl i . \ci l~ l i rrr~ryrppronch (2 nd ed. . Baltimore, MD : Paul H. Brooke s. Reprinted with perm ission.

When the receptors send information to the central ner-s travel into the spinal co rd to ascend

ht touch, pain, and temperature reception. Recent evidenc e

x actions of the CN S in an oversimplified way is com mo n.esearch techniques an d technology becom e more sophis-eve a better understanding of the complexity of the CN S.Heimer (1983) reports that the ascending sensory path-

Th e first category is the nntprolnterd sy stet~ his is locat-ed in the anterior (front) and side portions of the spinalcord and appears to be responsible for processing pain and

temperature information. This includes the spinothatract, the spinoreticular and spinotectal tracts. Bethey are very closely related anatomically, damage toften involves damage to the others as well.

The anterolateral pathways synapse at the scord level that correspon ds to the receptor input locthe secon d neuron crosse s over to travel in the anterlateral aspect of the spinal cord to the thalamus, andto the se nsorim otor cortex. Collateral fibers synapsethe reticular cells in the brain stem en route to the tmus . The spinoreticular tract also s ynapse s in the rlar cells of the brain stem. Reticular connectionimportant when examining the characteristics of aroTh e second category includes pathways for touchsure, vibration, and proprioception. Although the dc o l u m t ~ s ave been seen classically as the pathwaycarry out these functions. recent studies have showthe dorsolateral jbsciculus (which lies just laterathe dorsal columns and the posterior horn of thematter) also carries this information , especially frolower extremities. Researchers have also shown processing of touch-pressure input via anterolpathways.


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T B L E 8 2Reasons for Incorporating Various Sensory Qualities into Integrated Intervention Programs

Sensory System ArousalIAlerting Descriptors DiscriminationIMapping DescriptorsFor all systems

Somatosensory

Vestibular

Proprioception

Unpredictable To develop an increasing levelof attention to keep the child interested in thetaskhctivity (e.g., change the position of theobjects on the child s lap tray during the task).Light touch To increase alertness in a childwho is lethargic (e.g.. pull cloth from child sface during peek-a-boo).Pain To raise from unconsciousness: todetermine ability to respond to noxious stimuliwhen unconscious (e.g., flick palm of hand orsole of foot briskly).Temperature To establish awareness of stimuli:to maintain attentiveness to task (e.g., use hotfoods for spoon eating and cold drink for suck ingthrough a straw).Variable To maintain attention to or interest inthe task (e.g., place new texture on cup surfaceeach day so child notices the cup).Short duration To increase arousal for taskperformance (e.g.. tap child on chest beforegiving directions).Small body surface contact To generate andfocus attention on a particular body part(e.g., tap around lips with fingertips beforeeating task).Head position change To increase arousal foran activity (e .g., position child prone over a w edge)Speed change To maintain adequate alertnessfor functional task (e.g., vary pace while carryingthe child to a new task).Direction change To elevate level of alertn essfor functio nal task (e.g., swin g child back andforth in arm s prior to positioning him or her atthe table for a task).Rotary head movement To increase arousalprior to functional task (e.g., pick child up fromprone [on stomach] facing aw ay to upright facingtoward you to position for a new task).Quick stretch To generate additional muscletension to support functional tasks (e.g.. taptnuscle belly of hypotonic muscle whileproviding physical guidance to gra sp).

Predictable To establish the child s ability toanticipate a programm ing sequence or a salientcue; to decrease possibility to be distracted froma functional task sequence (e.g.. use the sameroutine for diaper changing every time).Touch pressure To establish and maintainawareness of body parts and body position; tocalm a child who has been overstimulated (e.g.,provide a firm bear hug).Long duration To enable the child to becomefamiliar. comfortable with the stimulus: to incorporate stimulus into functional skill (e.g.. grasp-ing the container to pick it up and pour outcontents) .Large body surface contact To establish andmaintain awareness of body parts and body position; to calm a child who has been overstimulat-ed (e.g ., wrap child tightly in a blank et).

Linear head movement To support establish-ment of body awarenecs in space (e.g., carrychlld around the room in fixed position toexplore its features).Repetitive head movement To provide pre-dictable and organizing information; to calma child who ha s been overstimulated (e.g ., rockthe child).

Sustained tension To enable the muscle torelax, elongate, so body part can be in moreoptimal position for function (e.g., press firmlyacross muscle belly while guiding a reachingpattern; add weight to objects being manipulatedShifting muscle tension To establish fun-ctional movements that contain stability andmobility (e.g., prop and reach for a top; reach,fill, and lift spoon to mouth).


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T B L E 8 2 CON T I N L I E D )Reasons for ncorporating Various Sensory Qualities into ntegrated ntervention Programs

ensory System ArousallAlerting Descriptors DiscriminationIMapping Descriptors

Auditory

Olfactorygustatory

High intensity: To increase opportunity tonotice object; to genera te arousal for task e.g.,cover blocks with foil for manipulation task).High contrast: To enhance possibility oflocating the object and maintaining attention tot e.g., place raisins on a piece of typing paper

for prehension activity).Variable: To maintain attention to or interest inthe task e.g., play rolling catch with a clea rball that has moveable pieces inside).Variable: To maintain attention to or intere\t i nthe task e.g., play radio station after ac t~ va tin gswitch).High intensity: To stimulate noticing the personor object; to create p roper alerting for task

perform ance e.g., ring a bell to encou rage thechild to locate the stimu lu\).

Strong intensity: To stimu late arousal for taske.g., child sm ells spaghetti sauce at lunch).

Low intensity: To :~llow he visual stimulus toblend w ith other salient features; to generatesearching behaviors. sin ce characteristics areless obviou s e.g., kind own cubby hole in bacof the room).High similarity: To establish more discerningabilities; to develop skills for naturally occurritasks e.g., scoop apple sauce from beige plateCompetitive: To facilitate se arching; to increatolerance for natural life circumstance s e.g.,obtain correct tools from equipment bin).Rhythmic: To provide predictable and organizing information fo r environmental orientatione.g., sing a nursery rhy me w hile physicallyguiding motions).Constant: To provide a foundational s ti~ nu lufor environmental orientation; especially impotant when other sensory systems e.g., vision,vestibular) do not provide orientation e.g.. chirecognizes own classroom by fan noise andcalms down).Competitive: To facilitate differentiation ofsalient stim uli; to increase tolerance for naturalife circum stances e.g., after child learns to lowhen his or her name is called. conduct activitwithin busy classroom).Noncompetitive: To facilitate focused attentiofor acqu iring a new and difficult skill; to calmchild who has been overstimulated e.g., movechild to quiet room to establish vo calizations).Low intensity: To allow the auditory stimulusblend with oth er salient features; to generatesearchin g behaviors since stimulu s is lessobviou s e.g., give child a direction in anormal volume).Mild intensity: To facilitate exploratory behaviors; to stim ulate naturally occurring activitiese.g., smell of lunch food is less distinct, so

child is encouraged to notice texture, color).From Dunn, W. 1991 ). The sensorimotor sys tem s A framew ork lor assessm ent and intervention. In F. P. Orelove D. Sobsey Eds. ), Educnt ing chd wrr ~ i t / i ~ I I I I I ~ ~ I Li . s d ~ i l i t i e ~ :trut~.sdi.~ ~i/~li~~~~r~11)l>ro(r(.h2nd ed. ). Baltimore, M D : Paul H. Brookes. Reprinted with permission.


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T A B L E 8 - 3 C O N T I N U E D )Examples of Observable ehaviors That Indicate Difficulty With Sensory

Processing During Daily Life TasksPersonalHygiene ressing Eating Homemaking SchoolIWork Play

cries when hair is distracted by is distracted bydrye r is turned on clothing that noise of utensils

becomes upset makes noise (e.g., against each otherby running water crisp cloth, acces - (e.g., spoon in

jerka when toilet w rie s) bowl, knife onflushes plate)

can t keep eatingwhen someonetalks

is distracted by is distracted by lay is disrupvacuum cleaner squeaky wheel- by soundssw nd cha i r makes sound

is distracted by is intoler ant of constantlyT V or radio during noise others maketasks in the room

overreacts todoor c losing

notices toiletflushing down thehall

gags at taste of overreacts to tolerates nar- heco me\ upset overreacts to tastes or smeloothpaste clothing when it row range of food s when house is new person (new all objects befo

jerks away at has been washed becomes upset being cleaned sm ells) playingsmell of soap in a new detergent when cerlain hot (odo rs of intolerant of

foods are cooking c leansers) scra tch-n-sni ffstickers

smells every-thing

W. 1991 . The sensorimotor systems: A framework for assessment and in trrw nt~ on .n F. P. Orelovc D. Strhsey (Eds. ) . E t I~ l ( ~ l t i~lrl \r.ith rn ~~ lti pl eli.sohi1itir.s: A trtr~~ stlisc il~li~r~~ryI / J / J ~ O U C ~2nd ed.). Baltimore. MD: Pi1111H Bruokes. Reprinted with permission.

The dorsal column fibers take a somewhat different routeto the thalamus and cortex. The neuron at the receptor sitetravels into the spinal cord and direc tly up through the pos-terior columns to the medulla (the lowest portion of thebrain st em ). At this point, a synapse occu rs and the newfibers cross to the other side of the brain stem and travel tospecific parts of the thalamus (ventrobasal complex ofthalamus). This set of neurons synapses in the thalamusand then the next neutron carries information on to the sen-sorimotor cortex. specifically the postcentral gy ms of theparietal lobe. The postcentral gyru s contains the m ap of anindividual s body from a senso ry point of v iew. It is fre-quently referred to as the sensory homu nculus.The fibers that travel in the dorsolateral fasciculussynapse at the cervical level and the spinal cord . Th e newneuron crosses to the other side of the spinal cord andtravels with the spinothalamic tract to the thalamus andon to the cortex. Th e source of som e of the earlier confu-sion about the function of the ascending p athways is dueto the mixed anatomical and functional relationship ofthe dorsolateral fasciculus with the dorsal columns andthe anterolaternl system.

3. Th e third functional category reported by Heim er (includes the unconscious prol r ioc~ptivepathwaysspinocerebellar tracts serve the very specific functproviding the cerebellum with direct accurate seinformation before it is processed at higher levels brain. These pathways travel directly from the reside through the spinal cord and into the cerebePathways such as these allow the cerebellum to otrate motor activity through access to the sensatiostimulates a response. The higher motor centers alsprocessed information to the cerebellum, and so aparison takes place between the original stimulus anprocessed information in order to plan the motor correctly. One can experience the action of the uscious proprioceptive pathways when attempting trect one s own m ovemen ts. The cerebellum comparplan and the sensation to determine whether an altemust occur. It is this process that allows one to knocking a glass over by picking it up correctly.Acknow ledging th e functional significance of the anical relationships among these pathways is important.

somatosensory sensations are ipsilateral to the pathway


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TO CORTEXt t . TReceptive field Neuron I I

Neuron 3 IReceptive field 3Receptive held Neuron

8 1. Three overlapping receptor fields send information

TO CORTEX

Receptive held Neuron I

Receptive held Neuron IReceptive held 3 Neuron 3

8-2. Three receptive fields thot do not overlap. Separate

Structure and unctionThe vestibular system makes a unique contribution to the

in the environment i.c., person-environment

In the jinul una lysis, one ma? have r ~ ~ 1 1 - d e l ~ l -o p d S C ~ J O I ~ .zcp o f rlre external world untl o cvell-

Figure 8 3. Schematic diagram of the somatosensory pathw

tlevelopc~dmotor rnup ofinoi1ement flom one yluce ttrnothrr; but jf one does not know where t h q are witrtJ.~pt2(.to thut nwp, thty ure v ir tuul ly incqablc o~ ts ing thu t spu / i (~ Imapping infhrm ution. And thvestibuklr system uppo urs to he thc system that givriilfi7rmuti017 uhout the in d iv id u d ~ ocution in thovrr t~ l lrputitd mup (Co ol, 1987 p. 3 .The vestibular organ is comprised of five compon

three semicircular canals and two chambers. Collectthey respond to type, direction, angle, and speed of mment, and head position. Information from these recsites combines within the CNS to determine the exact otation of the head. Receptors in the three semicircular care most sensitive to angular movements. whereas the rtors of the chambers are responsible for linear moveHeirner, 1983; Kornhuber, 1974; Goldberg Ferna


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. Gravity provides a major so urce of information for theThree setnicircular c~mnuls re located in each inner ear.

room. If on e would place on e semicircu lar canal on each

thees in one direction, the canals on one side will pro-

n excitatory resp onse while the correspo nding canal ona differential

ows the brain to interpret the direction of head mov emen t.To fire the vestibular nerve, there must be a change inition. rate acceleration or decele ration), or direction

a person is engaged in aangular movement such as spinning at a constant

utriclr and the succule. The

ng a whee led toy or in a car provide line ar stimulation.Direct input from the vestibular organ travels to the

nuclei at the pontom edullary junction of the brainand to a specialize d portion of the cerebellum dedicat-to vestibular processing the flocculono dular lobe). Th e

ebellar connection s are critical for postural co n-

sensory information is organized to produce basic

Postural ontrol NetworkThe postural control network is comprised of three prima-

descending motor pathways that work together to createivities. Th e l trrercrl ~~~stibulospinulruct is the largest

i t facilitates the extensor muscles, especially ine upper trunk and neck Heim er, 1983 ; Noback

). The med id ~~e~s t ibu losp inu lruct is a smallthird pathway establishes the balance of power within the

reticulospinal tract provides additional supportwork together to mod ulate body posture Figu re 8-

The v estibulocerebellar connections a re w ell-documented

Crdn ~a l e rve \I IV, VIw v e eye rnu\cle\

Laaral ve\libulospinal rr cl Ikld

igure 8 4. Postural control networknance of posture and orientation. As stated above, the bellar connections with the vestibular nuclei providinhibitory control necessary for maintenance of posture

Postural control is a basic. primary functional behEven in controlled studies where the vestibular orgabeen re mo ved , there is a serio us initial chan ge in posturability but within a short period of time compensatory areinstates som e of the functions that have been lost DSmith, 1984). It is believed that other reflexive and sesystems which contribute to postural control as wellover the orientation functions. Dependence on visuaproprioceptive input seem s to occur when vestibular inno longe r available. The interrelationships am ong the sry systems form the core of the multidimensional mapallow appropriate interaction of self in the environmenJongkees 1 974) states:


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The vestrhrdar organ is only one o f the organsthat infiwm us ahorrt our-position in spuce. It cooper-ates with visual und kinesth etic sen.\utions frorn rnus-cles, joints, e tc. As lon g as the infi)rinution rom thesevrrrious sources is the .same, we are well-infbrmedabout ou r position and o ur movernent.v cuzd e l3 e rything is balanced. i t as soon as thev do not agrerou r hnlance s lost and we are .sub/e~.to the fright-ening s ~ n s ~ ~ t i o nj 'hal~ ingost contc~ctwith the worldurourzd us (17. 114 .The vestibular system acts as the silent partner during

1974). When an individual is carrying out a task,

tically maintain the body's dynamic ori-

corporal potentitrlity to

1 s must

Vestibulo ocular PathwaysThe vestibulo-ocular pathways enable the individual to

movements. The medial longitudinallus (MLF) travels within the brain stem connecting the

111 IV. and VI. the

on (e.g., nau-sickness. Kornhuber I 974) related motion sickness

i t establishes the relationshipstterns of stimuli and particular autonon~iceactions.

Connections and Higher Cortical ConnectionsPhysiological studies have demonstrated that certain

brain centers produce short latency (quick) responses avestibular stimulation. For example, through the collaconnections with the reticular cells, it is thought that vestlar information reaches higher centers of the brain for aroand alerting responses. Reticular cells connect with the bic system and would thus be associated with emotional fings related to the movement experience.Some evidence shows connections to the thalamus wis the major integrating structure for the cortex. Simple mal experiments show that various portions of the thalamay respond to vestibular stimulation including the venposterior-inferior nucleus (a sensory relay area) of the thmus, the ventral lateral nucleus (although its primary romotor relay) and the medical geniculate body (an audirelay area) (Abraham, Copack Gilman, 1977; ButtneHenn, 1976; Deecke, Schwartz, Fredrickson, 1Liedgren Rubin, 1976; Magnin Fuchs, 1977; We1966). Several authors have postulated that collavestibular fibers enter the lateral geniculate body (a virelay area) to signal the visual system to prepare for potehead movement, so that visual images can coincide with and eye movement and the individual can maintain orietion in space and time (Kornhuber, 1974). None o tauthors cite specific locations as solely vestibular relays,conclude that vestibular information is integrated with otypes of information at the brain stem and higher le(Darian-Smith, 1984). This hypothesized pervasive influis compatible with clinical observations of disorientawhen a child or adult has vestibular dysfunction.Connections to cortical regions are also being stu(Darian-Smith, 1984). Two regions in the parietal lobe been sited as the most likely locations for vestibular procing: the inferior temporal lobe and a portion of the primsensory areas of the parietal lobe. Darian-Smith (1hypothesizes that the first region is related to one's pertion of the body in space, while the second area seemrelate vestibular input to the motor output that is generby the molor cortex.

Muscular Afferents Proprioception)Muscular afferents, usually discussed as part of the msystem. are receptors housed within the muscle belly, dons, and joints to provide ongoing information to the about the integrity of the muscle. Most people are famwith these receptors as the rnliscle spiwdles and Go lgi tenorgan (GTO). These receptors provide an excellent examof the intimate relationship between sensory and motor ftioning within the neuromusculoskeletal system.

The muscle spindle is a small muscle fiber surroundeconnective tissue that is housed within the fleshy part omuscle belly. These encapsulated fibers are dispe


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es in muscle integrity. The muscle spindles are respon-The muscle spindles contribute to function called auto-

nic juc i l i t rk m which is the ability to stimulate one's own

hed and the action can stop (Crutchfield Barnes,The muscle spindle may play an important role in ini-

h the movements (Crutchfield Barnes, 1984).Although spinal cord action is the focus when studying the

The inhibitory control from higher centers is lost, releas-the muscle spindle from this modulating influence. When

Barnes, 1984).The Golgi tendon organ is located within the tendons at

belly. The GTO is interwoven withincollagenous fiber so that when changes in tendon tension

Autogenic inhibition is the process of

Through this mechanism, the GTO seems to contribute to

Barnes, 1984).Because the GTO inhibits its own muscle and excites the

ons rely on co-con-

traction, as do goal-directed movements which are suppby a stable joint or body area. Stability can be providedproximally and distally. Movement of extremities is suppby trunk stability (e.g., reaching for a glass on the couwhile movement in the trunk can be supported through stty in the extremities (e.g., when an individual stabilizesarms and hands to move the trunk to perform a handstand

By understanding the concepts of autogenic faciliof the muscle spindle and autogenic inhibition of the Gthe therapist can better control the sensory and motor ronment when planning intervention. For example, a stretch activates muscle spindles (changes in muscle leengaging autogenic facilitation of the stretched muwhereas a maintained stretch past the tension state omuscle is more likely to fire the GTO-producing autoinhibition. relaxing the muscle being stretched.The Visual ystem

The visual system is one of the most advanced sesystems in the human organism. Although cell clustersearly in fetal life, this system becomes most functional postnatal period. Vision is the most prominent sensthere are more fibers in the optic nerve than in a11 the sry tracts in the entire length of the spinal cord (KandSchwartz, 1985). Because of its anatomical organizfrom the front to the back of the cortex, it also providexcellent vehicle for localization of CNS problems.

RetinaThe retina is the receptor mechanism of the visual

tem. The retinal cells have been studied extensively becthey are an extension of the CNS. When the CNS envment has been altered in a way that might affect the cells or supporting structures, these changes can be obsin the retina. The retinal cells operate to maximize the rtion of both light and color. Additionally, the cominterneuron network is set up to facilitate the transmissithe clearest visual image through lateral inhibition of nboring cells. Specific retinal cells activate a specific nerve cell; this pattern of organization continues to the oital lobe. This topogr phic or retinotopic organization athe cortex to construct an accurate and reliable map ovisual environment.

Visual athwaysThe pathways for visual input travel from the front o

cortex (behind the eyeball) to the back (occipital lobeother sensory systems ascend from the receptor site to thtex. This makes the visual system quite vulnerable to all of cortical damage, but also provides a consistent sourdiagnostic data for localizing the injury site. As with


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ateral

light reflexes\ 1 \I Pretectal region

8 5. Schematic diagram of primary visual pathways.


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of the visual pathways.The first visual system is referred to as the geniculocal-

or geniculostriate system (Noback Dem arest,T he nerve cells exit the eyeba ll, having obtained input

optic nerve covers the regionoptic chinsm. Com plete severing of thenerve results in total blindness of the eye serve d. At the

chiasm , central vision is carried through nerve c ells thatgence point. Peripheral vision is carried through nerve

tunnel vision.After passing through the optic chiasm region, the fiberway is known as the optic tract; these fib ers travel to the

eral genicula te body (a nuc leus of the thalamus). T he opticld. Just after exiting the lateral gen iculate body, the fib ers

avel forward and out before coursing ba ckw ard; this curvedis necessary so that the fibers can travel a round the lat-

ations. As with the op tic tract, the optic radia tions carry

arine sulcus (area 1 7), hence the na me g eniculoca lcarineThe geniculocalcarine system seem s to provide answers

the question What is it? 'b y gathering information about

s allow the individual to determine the identity and fun c-on of o bjects.

The second visual system is called the tectal system. Theal system seems to answer the question Where is it? by

ough the optic nerve, ch iasm and tract, but synapse in thethe midbrain is the highest portion of the brain stem and

tectum is made u p of the supe rior and inferior colliculi.)

ns, it is also a relay station for s omato sensory and audito-input (Kandel Schw artz, 1985), allowing a coordin ation

An individual with cortical brain damage may alert to

stem level, but will be una ble to follow through with adirected behavior related to the stimulus because theways that lead to the cortex are disrupted.

Visual System unctions and Therapeu ticInterventionsThe visual system is designed to recognize con(Kandel Schw artz, 1985). Wh en the visual environm

diffuse or homogeneous, the cells of the visual systemdifficulty responding. They search for the highest copossible, attem pting to make this area distinct. Th e eyetinuously change position with very tiny movements tovate new retinal cells. In this way, the brain gets oninformation about the object and can keep the image Busy visual env ironme nts can be difficult for the visuatem to handle. With too many competing images, the system cannot isolate significant high-contrast locatigenerate the nerve impulses. For example, think of hoficult it is to find something in the junk drawer kitchen. This is because there are many overlapping tives of varying shapes, sizes and colors; the competitso great that clarity is frequen tly lost.

Altering the sensory environ men t to increase the chfor success in task performance enables the individactively engage the environ ment. Thi s in turn increasesrate and reliable sensory feed back that can be stored anfor future tasks. Therapists can improve orientation in aally disoriented individual by providing a high-contrasal environme nt. For example, one cou ld place a dark cboard on the countertop to help distinguish light-cfood items when p reparing food. Contrast between thcovering and the nightstand in the bedroom would facgetting on the bed. Therapists can advise clients of wminimize problems with visual competition by orgacabinets, shelves, and drawers into sections for premined items or placing tool outlines (shadows on waracks to show which utensils or tools belong in eachtion). This not only provides a high contrast foregrbackground for the items, but also minimizes stackcluttering of objects on top of each other.The most common visual field defects that therencounter are tunnel vision (loss of peripheral visionhomonymous hetnianopia (loss of one side of the field). Figure 8 6 demonstrates w here these problems octhe pathways. Because visual field loss is often permancan have a significant impact on task performance. Cothe risks that are present when peripheral vision is not able to an individual. Many stimuli to which people attefirst noticed in the peripheral field, and much of one'sorientation relies on peripheral field input. Therapeuticvention must incorporate patterns of movement that cosate for the loss of peripheral vision. For example, one c


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Optic chiasmOptic tracts4

Lesion D

ccipitallobes

LLesion A results in right eye blindness. LLesion B results in loss of peripheral visio n tunnel vision ). @Lesion C results in loss of contralateral visual field.* LLesion D results in loss of contralateral visual field* @C D lesions yield same loss homono mous hemianopsia).

igure 8 6. Ne ur a l l e s i o ns a n d v i s ua l f i e ld de f i c i t sthat require the individual to move th e head from

wider area (e.g., placing impo rtant stimuli to theAutomatic use of head turning and body repositioning

Homon ymous h emianopsia is the loss of one side of the

ianopsia frequently comp lain that objects are miss-

sual field. This can be achieved by turning the head

Th is new position facilitates more aw areness of

one. For example, one can place items that are most imptant to the individual in the lost visual field to increase hturning to look for them, or play a card game and place deck in a position to facilitate head turning. Auditory csuc h as look to the left, Mr. Jones can be helpful initiabut there is a danger that the individual will become depdent on cu es from others an d never internalize this adaptafor independent task performance. Family education is important to balance eme rging adaptive behavior with safuditory System

Structure and unctionThe auditory system is also one of the newer sens

mechanisms in the CNS. The auditory system processound primarily for communication, but also as a meansenviron men tal orientation. Direction, distance, and qualitsound all contribute to the ability to orient within our eronment f rom an audi tory perspect ive (Kiang, 19Although other professionals specialize in working wproblems of the auditory system, occupational therapmust also be aware of the basic mechanisms within the atory system so that therapeutic approaches and environmtal adaptations can accommodate functional difficulties might arise from dysfunction in this system.

The auditory receptor is divided into three sections:outer, middle, and inner ear. Through these three comnents, airwaves are transformed into pressure waves withfluid system. The pressure waves displace hair cells locin the inner ear an d this action fires the nerve cells. Th e oear consists of the auricle (the part of the ear visible to the ear canal, and the eardrum or the tympanic membraTh e outer ear is vulnerable to obstruc tions in the can al or forations of the eardrum, both of which diminish hearingthat side.

The middle ear is a chamber that contains three smbones (malleus, incus, and stapes) and two small mus(tens or tympani and stapedius). When the ea r drum vibrathe small bones vibrate, which then emits pressure onsurface of the inner ear (cochlea). Th e Eustachian tube cnects this self-contained chamber with the throat to provipassageway to equalize pressure in the middle ear. Eustachian tube is frequently the site of infection becbacteria or viruses can easily get trapped within its sdiameter. This blocks the passageway into the middlemaking the pressure increase. Ear infections such as thoccur frequently with young children, partly because tEustachian tubes are less angled, allowing for less efficdrainage. This is a major reason why many children hplastic tubes placed in their ears during early childhood.tube is inserted through the eardrum and provides an a


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I M P ~ . E M E N T I N GE U K O S C I E N C ERI NCI PI .ESO SUP POK T ARII. ITATIONN D RE OVERY

nate means for pressure maintenance in the middle ear.Th e cochlea is shaped like a snail with several cham bers

inside. The movement of the fluid within these chambersallows displacement of the hair cells. When the hair cells aredisplaced, the auditory nerves fire. Specific hair cells areresponsible for specific sounds, and fire specific nerve cells.This process is known as torwtopic organization and is themechanism by w hich the CNS can identify the sounds heard.

The central connections of the auditory system areunique in comparison to other sensory systems. Figure 8 7illustrates the auditory pathw ays. Th e ascending pathwa ys ofthe auditory system are bilateral in nature: this is significantbecause loss of the input on one side will not completely sto pthe information processing to both sides of the brain. Interms of functional performance, the individual experiencesinability to localize soun ds from the environm ent with loss ofhearing to one ear or auditory nerve. Under normal condi-tions, the brain is able to compare the loudness of the sou ndsfrom the two ears to determine from which direction thesound is coming. Wh en o ne ear has lost its ability to transmitinformation, the brain no longer can locate the direction,hence the person can hear the sound clearly, but has more dif-ficulty finding it. Clinically, these individuals respond tosounds by changing posture or looking around to search forthe origin of the sound.

These bilateral connections in the ascending auditorysystem extend throughout the brain stem. The inferior col-liculus is a major relay point for auditory fibers (remem ber itis in the midbrain and is part of the tectum as described in thevisual se ction). Th e inferior colliculus functions to alert theindividual to auditory stimuli in the environment. From thebrain stem, information travels to the medical geniculatebody (in the thalamu s) and the temporal lobe.

The auditory system also has a feedback mechanism thatperforms an important function. This feedback system fol-lows a similar course as the ascending pathways but in amore unilateral pattern. This fibe r pathway inhibits hair cellscarrying extraneous or unimportant background noise fromthe environment, thus allowing the individual to attend toimportant sounds. This process is called auditory figure-ground perception. This is the mechanism which allows stu-dents to filter out such noises as rustling pape r and shufflingfeet in the classroom so they can hear the teacher s voicemore clearly.

uditory System Intervention pproachesAlthough othe r professions may test the auditory system

in more detail and may work on specific auditory compo-nents in their intervention plans, the occupational therapist isresponsible for the effects of auditory deficits on task perfor-mance. Therapists must decide whether intervention shouldbe set up in a quiet isolated place to avoid noisy environ-

edialgeniculate

Figure 8 7. Schematic diagram o f the auditory pathwaysments and decrease the am ount of effort required by thtory system or in a more natural environment in whindividual must develop inhibitory skills. Both choictherapeutically sound, but must be actively chosen as the intervention go als. For example, the therapist may to work in quiet environments early in the intervprocess so that other areas of conc ern such as posturtrol can be addressed without competition. The thmight choose a simpler postural task while workinmo re competing auditory environment to help the indlearn to screen out the extraneous noises that will alwpart of the natural environment. A portable tape recordearphones are helpful to introduce controlled auditoruli, which can later be incorporated into other activititherapist can control the type of sound (e.g.. clinicclassroom noise, neighborhood noise, music, talking) volum e on the tape s o that as the client adjusts to one


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1 3ALU3S

1 1~M 3J

SA


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fronta

Figure 8-8. Sensory cortical areas that provide direct input to the motor cortex areas 4,6 .reticuluspinal tract The coordination of excitation and inhi-bition of these pathways enables persons to hold and shiftposture with and against gravity.

Limb ontrolThe third category of motor output pathways serves limb

control. The descending pathway that serves this function is thecorticorubruspir zal pccthwti\; (i.e., from the motor cortex throughthe red nucleus in the brain stem and onto the spinal cord).

Understanding the organizational structure of thedescending pathways is important, because many times per-sons who have had brain injury will have differing levels offunction for each category of movement. This happensbecause brain injury can affect these pathways differentlydue to their anatomical locations. For example, some personswill have a harder time moving the limbs, but can performfinely tuned movement in the hands when they can rest thewrist on a surface, thereby avoiding the limb control issue.

Another person may have difficulty with postural controcan turn the head to interact with others or bite and chewing a meal if the body can be stabilized in supported seOccupational therapy personnel can design more effadaptations when these subtle movement differences fnervous system perspective are understood.The erebellum

The cerebellum is a fascinating internal structure oNS whose job is to orchestrate motor activity. The ce

lum is located just behind the brain stern and just undoccipital lobe of the cortex. The cerebellum is able to otrate motor activity by monitoring the ongoing sensorythat contributes to the need to move, and by comparininput with the early drafts of one s plan about movingcomparison enables the cerebellum to make adjustmethe motor plan before the message to execute the action is activated.


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vestibular nuclei

Exit ircuitry for theSomatic Motor SystemA Postural Control: Med ial Lateral VestibulospinalReticulosp inal TractB. Limb Control: Corticonu brospina l TractC. Finely Tuned Movements: Corticobu lbar Face Head via CranialCorticospinal Hand s

Figure 8 9. Exit circuitry for the somatic motor system


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~ ~ ~ I ' L E ~ ~ F . N T I N GE U R O S C I E N C EKIN(:IPLESO SUPI'ORTHAKILITXI IONN D &


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/ = to exit circuitrysensorimotor see Figure 8-9)

H ere 's H o w t o M o v e

Schematic diagram of the interaction of the internalmotor circuitry1 . The pathways of the sensory systems provide inp ut to the sensorimotorcortex via the spinal cord, b r a r stem, thalamus directly to the cerebellum.

spin ls t e p c o r d 2a.b. thearlyarlyLet'snformationnformationo message,ss sentent too hichhehe basalerebellums sentanglia,o theherehichhalamus.t is rocessesatched twi tho formhesensory messages; from this input the cerebellum.

3 . The ventral lateral nucleus of the thalamus com bines the messages andsends a refined message to the mo tor centers, and they trigger theinform tion from app ropriate exit circuitry (see Figure 8-9).sensory systems8 10. Schematic diagram of the interaction of the internal motor circuitry


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~ ~ P I . E M E N T I N C ; EUROSCIENCER I N C ~ P L E SO SUPPORT ARII ITATIONND (:OVEKY

M ajo r Thalamic nucleiR la teral vent r ic le g lobus pa ll idus o fth e basal gangl ia

p u ta m e n o f t h ean te r io r basa l gang l ia

la te ra l su lcus

t h i r d M G Bventr ic lep o s t e r i o r

PFVAv LVPD MM G BLG B

ant er ior nuc leuscent romedian nuc leuspu lv ina rparafasc icular nucleusven t ra l an te r io r nucleusven t ra l la tera l nucleusven t ra l po s ter io r nuc leusdorsom edia l nuc leusmed ia l gen icu la te bodyla te ra l gen cu late body

igure 8 11. Anatomy of the thalamus internal capsule an d basal ganglia


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T A B L E 8 6Functions of the Major Nuclei of the Thalamus

Thalamic Nucleus Cortical Connection Function SupportedAnterior limbic system emotional toneDorsomedial prefrontal lobe judgementlreasoningCentromedian reticular system generalized arousalIntralaminarMidlineVentral Anterio rVentral LateralPulvinarVentrobasal Complex*VP Lateral

*VP Medial*VP InferiorLateral Geniculate BodyMedial Geniculate Body

posterior frontal lobeassociation areasparietal lobe

occipital lobetemporal lobe

motor functionshigher cognitive thoughtsensory mapping (i.e.,somatosensory,somatosensory.vestibular)visual system functionsauditory system functions

all indications of a loss of the balanc e of pow er in the basal

or m aking it hard to en gag e in the activity at all.

Many believe it is erroneous to consider the function of

Dunn, 1991a; Kan del, Schw artz Jessell, 1991). Thesensory organs, process-

oskeletal system . The motor sy stems cannot operateut sensory information, either during the current ev entring a response, or from m emo ries of prior events whichd to construct maps of the body and the environment.

The thalamus is an integrating structure that sits in the(Figure 8-1 1). It is a critical structure

every single stimulus that goes to and from the(except olfaction) must travel through the thalamus

helping the o rganism to respond properly. Table 8 6 conta summary of the major nuclei of the thalamus, their sysconnections and the general function each nucleus suppoMotor Control

Mo tor control is the ability to m anage on e s bodymovement (Dunn, 199 b), but is different from praxis cognitive section below). We use movement sc hem a thathave created from experience or practice to make our moments m ore efficient. The motor cortex supports the sequeing, timing and maintenance of control over movementsthe motor cen ters of the brain rely on sensory informatioactivate the desired m ovements. There are several questithat therapists can ask themselves to identify motor coniswes that may be interfering with performance (Du1991c): Table 8 7 contains these questions.Principles for Designing TherapeuticInterventions ased on Motor SystemFunctions

The E HP fram ework outlines five intervention approaes that can be used to provide therapeutic supports. The interventions acknowledge the ways that therapists address not only person-related variables, but also task context variables that can affect performaEstublish restore interventions address person variables;therapist identifies the person s skills and abilities, designs interventions to improve them. When therap


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TABLE 8 - 7

Questions That Enable Professionals toConsider Factors That ffect Motor ControlCan the individual carry out discrete movements(those with a clear beginning and end)?Can the individual carry out movements that are in aclear sequence with each other?Can the individual carry out movements that arecontinuous (e.g., steering a car, holding onto a cupof water)?Can the individual carry out predictable sequencesof movement?Can the individual carry out movements when theenvironment is unpredictable?Is the individual's reaction time a pprop riate for thesituational dernands?Can the individual sustain performance for continu-ous tasks?Can the individual continue a repetitive movementpattern?Can the individual anticipate movement dem ands?Can the individual create the correct amount offorce, velocity, and co ntrol to carry out effectivemovements?Are there differences in performance between thefinely tuned movements of the hands. limb move-ments. trunk control and facethead control?

From Dunn, W. 1991).Assessing human performance related to brainfunction. In C . Royeen (Ed.), Neuro.vc.ier~ce fi~~fndution.rfhumun pe r -f i~rnlunce.Rockville, M D: AOTA. sed with permission.

daptive interventions address task and context vari-to do, and co nsiders the person's skills, the character-

nd available for eating, the therapist would design adaptivee guard and teach ing the person to use a rocke r knife forThe lter interventions require the therapist to under-

therapist identifies the best possible match between thson's skills and a particular performance context. important to remem ber abo ut the alter intervention is thdoe s not change the person or the con text, but rather finbest match between them. For example. if a person cerebe llar disorder. which results in the person having tion tremors and ataxia (i.e., lots of extra movements ever the person tries to move), a therapist might idenpolitical marketing firm for employment. because aworkers wear headsets, and this person could have exouos movements without this affecting the ability to tpeople on the phone about the candidates. The petremo rs do not go away fro m the intervention, and the fnot asked to make any changes in the job for the perso

Preventutive interventions occur when therapists useexpertise to anticipate prob lems in the future, and designventions to keep negative outcomes from occu n-ing. Whmotor systems are disrupted, persons commonly have lems with decubitus ulcers (i.e., skin breakdowns) onprominences due to their inability to move easily to shifture or position during the day. Therapists anticipate thmight occur, and design interventions with the person tvide cues throughout the day to remem ber to move bod yaway from weight-bearing surfaces.

T h e Create interventions address the larger contneeds of communities. Occupational therapists have etise that can make daily life more available, interestinenjoy able for everyone, not just those w ho have performneeds. We use create strategies when we apply occupatherapy ex pertise to make a context better for everyone,out concern for disabilities. For example, serving on amission to design the comm unity's d ay care environmeplaygrounds would be a create intervention. Working corpor ation to make the office building easier for everywork in (e.g., signage , friendly work stations, chair and work surface height options), or designing a commliving neighborhood for elders employs a create interveKno wledg e of the entire CN S is useful in identifyingative interven tions in this category.

Cortical Supports for Cognitive PerformanThe CNS is organized so that information can be

grated for complex thinking and problem-solving Integrating diverse information enables persons to amore difficult dilemmas than are possible with the mogular processing that is observable in less-evolved isms. General questions that providers can ask to detthe role of cognition in performance ar e provided in Ta


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T A B L E 8 8Questions That Enable the Professional to

Consider Factors That ffect CognitionAre basic sensory experien ces intact?Can the individual interpret incoming sen sory infor-mation in a reliable manner'?Can the individual organize and integrate complexconfigurations of stimuli?Can the individual create a plan to act on the inter-pretations and con figurations identified'?Can the individual use memory to support cognitiveactivity?Can the individual use resources to m ake effectivedecisions?Are there indications of somatic motor disruptionsthat would interfere with the manifestations of cog-nition?Are drugs affecting the individual's ability todemonstrate cognitive abilities?Do times of day affect cognitive performance?Are there any indications o f disruptions in biologi-cal rhythms that would d iminish cognitive abilities?

From Dunn, W. 1 09 ). Assessing human performance related to brainfuncticm. In C. Royeen (Ed.),Nruro.scirnce fo[~ncIc~~ic~~i.shurrrotr 11er-fOrmrrrrc~e. ockville, M D : AOTA. Used with permission.

8. Three key features of the cognitive systems in people arethe arousal and attentional mechanisms. the language andcommunication systems and the systems that support praxis.

rousal and ttentional MechanismsDeMoja, Reitano and Caracciolo (1985) describe the

relationship between arousal and performance as a complexmatrix affected by three variables: the structure of the indi-vidual's personality, the difficulty of the task, and the struc-ture of the situation in which the task is to be performed.Vinogradova (1970 ) described several events which m ustoccur in order for the CNS to register a stimulus. First, theappropriate receptors must recognize that a change hasoccurred in the environment. Second, the CNS must deter-mine whether suc h a stimulus has occurred before. Third, theCNS must decide whether or not to act on the stimulus.Finally, the CNS must carry out the decision. Further, itappears that under normal conditions the C NS tend s to inves-tigate stimuli that are not familiar and inhibit consciousawaren ess of familiar stimuli (McG uinness Pribram ,

198 0). Table 8- 9a provides a workshe et that enaproviders to consider the aspects of attention that mayaffecting performance.

As an example, think about yourself as a student in a oretical astronom y class. Althoug h you m ight have an inheability to initiate and hold attention to the typical featurethe classroom learning enviro nment (e .g., the teacher's vothe writing on the overhead, the pencil and paper for noteing), the subject matter content may force you to expendextreme amount of effort. The heightened effort might redyou r capacity. m aking it less possible to tolerate distractionthe class. Table 8-9b contains a completed form about exam ple to show you how this might look as a task is analyfrom an attentional perspective.

DeGangi and Porges (1991) describe the neural mecnisms that support arousal and attention. Th e sensory tems must be able to register that a stimulus is occurrinbegin the processes. Specifically, the arousallalerting aspof each sensory system (see Tables 8-1, 8-2, and 8-3 scollateral fibers to the reticular formation, a center arousal in the brain ste m. The reticular formation then seexcitatory information to higher centers in the brain. incing the limbic system (i.e., the hippocampus and the amdala if you are interested in the structures' names), the thmus and the cortex. The reticular mechanisms provide etation for the centers they conne ct with. m aking it easierthose centers to activate in response to additional input. Ia pay attention messag e for the othe r centers as mfocused information comes their way.

The Factors described above are all part of the functing arousal and attentional system. Each of these procecan be disrupted when the CNS is not functioning propewhen arousal and attention are disrupted, n person's permance is also placed in jeopardy.

Dunn (199 7) describes the interaction between the rological mechanisms that enable a person to notice respond to sensory stimuli and the behavioral responses sible as a model for understanding a person's repertoirbehaviors from a neurological point of view. Table 8- 10vides a sum mary of their proposal about this interaction.

A person's neurological thresholds refer to the amounstimuli necessary to reach a point of noticing or reacting tostimuli. Those who have high thresholds take a longer timreact; some neurological and social science authors refethis condition as habituation Wh en habituation is operatthe CNS is responding to the stimulus as if it is famirequiring little attention. Low thresholds, on the other htrigger more readily, and therefore cause the person to rmore frequently to stimuli in the environment. This heiened reactivity is som etimes referred to as sensitization

When addressing persons who have performance neproviders must observe behavior. The model in Table 8


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T B L E 8 1Relationship etween ehavioral Responses and Neurological Thresholds and the ehavioral

Repertoire that s Likely to be Present with Each InteractionNeurological Thresholds ehavioral Responses

respond in accordance with threshold respond to counteract threshohigh (hab ituation) poor registration sensation seekinglow (sensitization ) sensitivity to stimuli sensation avoiding

s neurological thresholds. First, person s can respond itthis suggests that their

with high thresholds w ould ap pear to respond to veryew stimuli, wh ile persons w ith low threshold s would tend to

respond tothresholds; sugg esting that persons behav-

al repertoires try to offset the impa ct of their n eurological

to keep from triggering their thresholds.All of these factors fall on a continuum related to the

ensity of respon se. For exam ple, persons c an hav e a slightf trouble registering stimuli. Sim ilarly, perso ns co uld tend

tem being more sensitive than the vestibular system ). Let

ruct effective interventions for persons demo nstrating these

oor Reg istrationWhen persons have difficulty registering stimuli due to

ey tend to have a dull or uninterested app earan ce. We know

extual cues. When serving persons who have poor regis-

t thresholds will be met. On e can increase the contrast and

o the task routine. With these p erson s, always think

of how to make the experience more dense or intensestimuli. The more they have the opportunity to triggerthresholds, the more they are likely to be able to deadaptive responses.

Sensitivity to StimuliWhen persons have sensitivity to stimuli due tothresholds and act in accordance with those thresholds,

tend to seem hyperactive or distractib le. The y have atime staying on tasks to complete them or to learn fromexperiences because their low neurological thresholdsdirecting their attention from one stimulus to the whether it is part of the ongoing task or not. When sepersons who have sensitivity to sensory stimuli, emphthe discriminatinglmapping features of sen sory systemTables 8-1 8-2 and 8-3): because these aspects of seinput do not increase arousal. These pe rsons need orgainput limiting distractions to draw them away from theat hand. For example, use touch-pressure to make corather than light touch; organize tasks to have linear mment rather than rotary movement. The more discriminamapping input these persons can obtain, the better chances for com pleting tasks and learning from them.

Sensation SeekingWhe n p ersons have high thresholds, but develop res

e s to counteract their thresholds, they enga ge in behaviincrease their own sensory experiences. These personmov ement, touch, sound and visual st imuli to every exence. They might sing to themselves. dance in theirtouch eve rything, hang on objects or people or chew on ta lot in an attempt to meet their high thresholds. Wh ening persons w ho seek sensation, it is important to first obthem carefully to obtain information about what sensathey add to their behavioral repertoire. The most effeinterventions for these persons inco rporate the sensatiopersons need into their functional life repertoires. For eple, if a person se eks mov ement input. but this is interwith functional life performance, tasks can be reconstrtasks to include more m ovem ent, so persons get the inpurequire as part of the daily life routine. In this exampl


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equire more walking, bcnding and reaching to get readye day. Honoring th e input they seek can also reduce a nx-

Sensation voidingWhen persons have low thresholds and develop respons-

thresholds; they might a ppe ar to be resistant and unw ill-

t is possible that these rituals serve to pro vide a pattern

tuals provides a wealth of info rma tion. It is often suc -n som e small way, so that there is a blending of Samil-

more.

The process of com mun icating includes consideration o f

ng and eye contac t, and other features of comm unica-on such as tone of voice or nonword sou nds as part of the

NS structures and systems to the process of havingadaptation to support comm unication. Table 8-1 pro-

d sum marizes the communication functions pre-to these centers.

As with all cognitive functions, communication is depen-rimotor processing. For higher corti-

(1991) suggested that four major integration centers supcommunication. The posterior purietal lobe organizes spdata for object localization ; when a person can organize to map the environment, communication about the enviment's makeup is possible. The inferior temporal lobe cbines information to create a map of the characteristicsplaces and things. or object identification ; one examplthis is facial recognition. Wernicke s area is located atintersection of the parietal, occipital and temporal lobes, processes information to enable the brain to interpret langu(i.e., receptive language). In the left hemisphere, Wemicarea processes speech com munic ation, while in the right hesphere Wernicke's area processes infor nutio n to interpret verbal communication. Broca s ureu is located in the frolobe, and through conn ections with Wemicke's area, integrinformation for expressive language.

raxisPraxis is a conceptual process by which the indivicreates, organizes and plans new motor acts. Praxis is a cceptual process. and not a motor act. Praxis is supportedseveral higher cortical centers, m aking it part of the cognprocesses of the brain. Evidence su ggests that praxis is clly related to the information available from the sensory tems: the more a task requires sensory input and feedbthe more task performance is adversely affected in conditof dyspraxia and apraxia. Figure 8-12 contains a diagramthe sensorim otor link s to the key m otor cortex structuressupport praxis. The dilemma for professionals is thatmust observe ou tward behaviors to make o ur interpretatabout a person's abilities; assuming that difficulty wmovement is au ~oniatically a m otor problem is an eTable 8-1 2 contains a list of questions that professionalsask when considering praxis as a factor in performaWhen considering the praxis aspects of performance. A(19 85 ) suggested that we consider three aspects of process: ideation, planning and motor execution.

Ideation is the formation of ideas about what a pemight want to do. It is an internal process in which the vous system either gathers information from stimuli inenvironment o r recruits inform ation from m emo ry stores stimuli from past experiences) to formulate an idea awhat to do. When individuals have ideational deficits. thenot have the capacity to figure out what can be dIndividuals with ideational difficulties display very simplor repetitive patterns of movement, illustrating their inabto formulate ideas for action. When serving persons who hideational praxis problems, we have to be very systematidesigning intervention activities. Intervention must builthe person's repertoire of skills; making a task too comtoo soon can immobilize the person from engaging in


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Can the individual underslanl wrllten inlormalion(read)? yes

Can the ind~vidual nderstand spoken informal~on(Wen)?

Can lhe individual repeal what someone else hasYes

Yessaid?

Can Ihe individual wrile legibly? Wilh coherentlhoughts?Can the individual vocalize? Convey coherenlthoughts?

Can Ihe individual read aloud? NO NO yes

No

Does the individual uselundersland intonation?

Yeses

No

No

I Yes i Yes

No

Can the lndividual spell? (Be sure lo check premorbidability.)

No

No

NO I NO

Can lhe ~nd~v~d ualse geslures lo commun~cate?Does the lndlv~dualecognize nonverbal cues (e glac~al xpressions, body poslures)7

Is the individual aware of own errors in talking, wriling? No Yes I

Can Ihe ~nd~v~ dualnderslandlcreale propor synlaxlgrammar?Is the ind~vidual's speech fluenl ( rate, rhythm okay)?

Can the Individual lmd the right word when lalking? I I

YesYes

8 1 1. Areas of the brain involved with lang uage functions (if the brain is damaged, can the individual perfo rm the specified task ?). From Dunn, W. 1991) .sing huma n performance related to brain function. In C. Royeen (Ed.), Neuroscience foundations o f human performance. Rockville, MD AOTA. Reprinted

No

Yes

YesYes

No

No

NoNo

No Yes


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HIGHER CORTIC L CENTERS

(hypothalamus and

EXTERNAL ENVIRONMENTopportunities to a c larousing sensory stimulisalient experiences

INTRINSIC DRIVEexplorationlearning.interaction1 lNTERNAL ENVIRONMENTbiological rhythmsHOMEOSTASISa. set pointI . crror sigc~al(homeostasis rlisrul~lccl)behavioralresponse

SensorimotorSystem NervousSystem (ANS)

igure 8-12. Factors which create the appropriate conditions for motivated behavior. From D u n n W. 1 991) . Motivation. In C . BRoyeen (Ed.),AOTA Self Study Series on Neuroscience Rockville, MD: AOTA Used with permission.environment. We must also create interventions whichenhance the sensory information available to the person, tobuild maps of self and environment for use in idea generation.For example, we might make objects heavier in a routine, toincrease the proprioceptive feedback for the person. We mightalso start with a routine that is in the person s repel-toire. andembellish the routine one part at a time. This allows the per-son to experience increasingly complex sensorimotor actionsto build neuronal models for engaging the environment.Increasing complexity leads to more advanced body and envi-ronmental maps which can be used for future idea generation.

Planning is the process of organizing information todesign method for responding to environmental demands.Planning is also an internal process which uses sensorimotorinformation to figure out an efficient and effective way tomove. The motor plan is not the movement itself. When aperson has difficulty with motor planning, he or she has theinformation needed to create the ideas, but has difticulty fig-uring out how to get his or her body to implement ideasabout moving. When persons have planning problems, theydisplay several types of movement difficulties. First, they

will be very clumsy; because they are unable to make a gplan, their efforts to move in response to environmdemands are inaccurate. Secondly, it is common for perwith planning problems to be able to verbally describe needs to be done; they have good ideas, but they are unto create a plan for doing it themselves. This charactercan extend to being bossy and directive: this is likely tocoping strategy for completing the task effectively, wreducing the possibility of errors that will occur if they tcarry out the task themselves. Sometimes persons with pning problems destroy objects more easily than others;may be related to their poor modulation of movemwhich can lead to holding something too tightly, dropobjects, bumping into objects, etc.

Providing intervention for persons with planning plems is challenging. Since they make a lot of errors, it is cmon for persons with planning problems to either quirefuse to try new things, or to make many mistakes. addintheir misperceptions about how to move. We must build ivention scenarios that provide a motor planning challebut we must also design the activity so that we can pree


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e by intervening hef ire the person makes an error. Whenhem, we allow incorrect patterns to form and we erod e

The third factor in the process is motor execution. This isMo tor execution is the acl of carrying out

t is what on e observes, but it is not praxis. W hen per-ve motor execution problems without praxis problems,

, i.e., they will be able to adjust the ir performanc e

ed on Cognitive SystemRemembering to address the cognitive aspects of perfor-

es and nee ds. In or der to get y ou started, Table 8 13 provideses of therapeutic interventions (using the E H P frame-

k) that an occupational therapist might de sign fo r selectedtive problems that are interfering with p erforman ce.

Emotional SystemStructure and unction of the Limbic SystemThe limbic system is an o lder, more primitive part of the

CNS. It evolved from the "smell" brain in othe r species ; thissmell brain was responsible for primitive instincts and drives(Moore, 1976). Th e primary structures of the limb ic systemare the limbic lobe (i.e., the cingu late gyrus ), the h ippocam -pus and the amygdala. The hippocampus is involved withstorage and retrieval of memory, and is implicated in demen-tia as tangles and placques form to reduce its function. Thearnygdala is involved with the ability to register sensoryinput, and contributes to the arousal/alerting mechanismsdescribed earlier.

Moore (1976) describes the functions of the limbic systemusing the acronym "MOVE " The word itself is important,because the limbic system supports our instincts to survive;however, she also used the letters to remind us of the primaryfunctions of the limbic system. The M stands for memory;

T A B L E 8 1Questions That Enable the Professional to

Consider Factors That ffect PraxisIs the individual aware of body parts and their cabilities?Does the individual demonstrate awareness of enronmental features that may affect performanceneeds?Does the individual have experiences to draw froto create an idea?Can the individual express or demonstrate aware-ness of ideas about how to accomplish a task?Can the individual ada pt performance to match tademands?Does the individual profit from observations anddemonstration or physical prompts?Does the individual notice errors in performance'Can the individual use common objects as theywere intended to be used?Does the individual create functional adaptation sthe use of common objects?Can the individual combine separate movementsinto a functional sequence?Are there specific areas of problem performance(e.g., postural, oral)?

From Dunn, W. (1991). Assessing human performance related to bfunction. In C. Royeen (Ed.), N e u r o ~ c . i n i c ~ r f o ~ ~ ~ ~ i / i ~ i io n sfhumcm forrnuric.c~.Rockville , M D : AOTA. Reprinted with permission.

this includes the instinctual, genetic memories and thecognitively oriented short- and long-term memory syTh e circuitry that is involved with the hippoc ampu s estaes ways to store and retrieve memories effectively. Eacson constructs individualized ways to use this system.

The 0 stands for the olfactory functions of the sThe olfactory system is a major input for the limbic cirand contributes to the rich memories persons have relatedsmells of their lives (e.g., being in grandma's kitchen bread w as baking; standing in the hay fields just after thvest). Th e direct neural connections make these m emorieintense and available even if they are old memories. Procan take advantage of these connections with persons wconfused by providing more familiar smells in the envirofor orientation; the odors can trigger memories when moditional cognitive strategies cannot. For example, a dacan wear her traditional perfume when visiting her mothspray the perfume on pictures of herself, so the mothe


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T B L E 8 1Examples of Therapeutic Interventions from the Ecology of Human Performance Framework for

Selected ognitive System DisruptionsPerformance ProblemsNeed and Neuro That re Restorative daptive lter PreventativeCorrelate Occurring Interventions Interventions Interventions InterventionsSarah is a school aged Sarah seeks auditory,girl whose parents movemen t and touchwant her to participate stimuli throughout thein her classroom day, which interruptsactivities: she has seatwork and classhigh sensory thresh - participationold5

Lana, an older woman Lana can tell youwho wishes to cook what needs to befor her grandchildren; done , but has troublehas apraxia carrying out the

movements herself;this sometimes causesfrustration

Presley, a young adult Presley doesn' t under-who wishes to have stand intonation, ges-friends; R hemis dam- tures, facial expres-age affects nonverbal sions; doesn ' t uselanguage centers gestures properly to

communicate

Swing and sing withSarah on the play-ground at arrival toprovide additionalinput so she can focusher attention whenshe goes to class.During seatwork,place Sarah's suppliesaround the room soshe can move about toget them as she w orksProvide physicalprompts and handover hand guidance toopen containers; pourand stir ingredients soshe can learn howmovements feel dur-ing the taskWatch movies togeth-er and talk about thegestures, facialexpressions, intonn-tion; practice havingthe same interactionas the movie

Provide seatwo rkdirections on tape, soSarah can listen tothem as needed tocomplete assignmenls

Purchase ready mademeals that can beheated up with thegrandchildren

Find a buddy to go tobook club with him;buddy will interveneto support his interac-tions

Work with parentsand Sarah to get herinvolved in the com-munity center danceclub, which h as bothactive, freestyle danc-ing and karaoke

G o to restaurants withgrandchilden as analternative eatingenvironment forsocializing with chil-dren

Identify an email bul-letin board for social-ization so that there isnot a requirement forusing or interpretinggestures. intonatinn

Have Sarah join thechoral group atchurch t o preventsocial isolation thatmay occur

Locate job possibili-ties and necessary joskills for employmento prevent restrictedliving options due tofinancial restraints

R E M E M B E R : the Create intervention is applied within the commun ity to benefit all pcrsons in the community of interest, and does not specificallyaddress disabilities.

The V stands for visceral connections. The limbic sys-

implementing neuroscience principles

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