robert a. leark, ph.d. fellow, national academy of neuropsychology

Robert A. Leark, Ph.D.Fellow, National Academy of NeuropsychologyAssociate Professor, Behavioral & Social SciencesPacific Christian College, Fullerton, CAVice President, Research & Development, UAD., Inc

Theoretical Models of Explanation


Multiple models of explanation for ADHD

Two have emerged as primary theories Barkley & Gordon Brown

Attention & executive functioning is multifaceted: difficult to map


Recent Historical Models Attention is not a unitary construct Zubin (1995): attention conceptualized

as having multiple components or elements

Psychiatric models:attention is process that controls the flow of information processing


Recent Historical Models Psychiatric models: 3 components of

attention:selectivitycapacitysustained concentrationAll of these must be sufficient enough to

interfere with daily activities


Recent Historical Models Neuropsychologists typically

conceptualize attention as:selective processingawareness of stimuli


Recent Historical Models Neuropsychologists use attention to

refer to:initiation or focusing of attentionsustaining attention or vigilanceinhibiting response to irrelevant stimuli

(selective attention)shifting of attention


Riccio, Reynolds & Lowe (2001) summarize components of attention

Arousal/alertness• motor intention/initiation

Selective Attention• focusing of attention (inhibiting/filtering)• divided attention• encoding, rehearsal & retrieval

Sustaining attention/concentrationShifting of attention


Historical Broadbent (1973) - capacity to take in

information is limited, thus information not relevant needs to be filtered out. Information filtered out dependent upon stimulus characteristics (intensity, importance, novelty, etc.)


Historical 2nd model stresses arousal - here

optimal arousal (alertness) is necessary for effortful, organized function (Hebb, 1958)

Pribram (1975) - arousal is short-lived response to stimulus. Arousal is the general state of the individual that allows for & effects attentional processing


Historical Mirsky (1987) proposed three factor

model for attentionfocusing of attentionsustaining of attentionshifting of attention


Historical Mirsky model

selective attention: part of process of focusing attention (level of distractibility if deficient)

Sustained attention: ability to maintain that focus over time

Shifting of attention: necessary for adaptation & inhibition


Historical Luria’s model

attention central to model2 attentional systems: reflexive & nonreflexivereflexive: orienting response/appears early in

developmentnonreflexive: result of social learning/develops

slowerlimbic system & frontal lobe mediate attention


Historical Luria’s model

executive functions linked to mediating attention

executive functions:• self-direction• goal directedness• self-regulation• response selection• response inhibition


Mesulam (1981): model similar to Luria’s Model was specific to understanding

phenomenon of hemiattention or hemineglect as result of brain damage

Attentional processes: reticular system, limbic system, frontal cortex & posterior parietal cortex


Mesulam (1981) Subcortical influences from limbic

system, RAS & hypothalamus part of system matrix needed for control of attention

Frontal lobes influenced by & also influence the subcortical activity


Historical Summary: attention involves at least

two separate neural systemsactivation system: thought to be centered in

left hemisphere & involved in sequential/analytic operations

arousal: thought to be centered in right hemisphere & involved in parallel or holistic processing & maintenance of attention


Barkley & Gordon (1994,1997,1998,2001)

inattention emerges alongside a general pattern of impulsiveness & hyperactivity

deficits in self-control lead to secondary impairments in four executive functions


Barkley & Gordon (1994,1997,1998,2001) Nonverbal working memory - sensing to

the self verbal working memory - internalized

speech emotional/motivation self regulation -

private emotion/motivation to the self reconstruction or generativity - cover play

& behavioral simulation to the self


Barkley & Gordon (1994,1997,1998,2001)

basal ganglia dopaminergic disinhibition key factor to etiology


Barkley & Gordon (2001) ADHD is a longstanding, pervasive and

chronically impairing consequence of poor inhibition and/or inattention

model is consistent with the DSM-Ivr criteria

symptoms occur prior to age 7


Brown (1996) etiology is on purely inattentive stresses there has been an over-focus

on disinhibition and an under appreciation of arousal, activation and working memory

onset of symptoms can occur after age 7


Brown ADHD criteria includes inattentive

individuals who are not impulsive “all inattention is ADD/ADHD” ADHD is a suitable diagnosis for a broad

range of symptoms Brown’s rating scale: BADDS - modeled

upon this theoretical approach


Brown - ADD/ADHD is still an executive dysfunction of five clusters organizing & activating to work sustaining attention & concentration sustaining energy & effort managing affective interference utilizing working memory & recall


Key components of models

inattention is the king of all nonspecific symptoms (Gordon, 1995)

inattention can emerge as a feature from a variety of psychiatric & medical circumstances

Clinical Care

History - conception through current age early life predictors

poor or inability to establish early life routinesmotor hyperactivity at early age

ADHD is a diagnosis by exclusion:low APGARhypoxiacentral nervous system diseases

Issues in Clinical Care

Clinical CareHistory

ADHD is a diagnosis by exclusion:head injury/loss of consciousnessmetabolic disordersseizure disordersapneaother medical conditionsOther psychiatric conditions

Clinical Care

History ADHD is a diagnosis by exclusion:

ADHD is diagnosed only when other disorders do not best account for the symptoms

symptoms may be same, etiology somewhat different (or unknown)

treatment may even be the same

Clinical Care

History Problems with overlapping co-morbidity

create need to be able to stick to DSM IV criteria: age 7 issue

May not be possible to determine if signs & symptoms might have been present (such as trauma-abuse cases) if such trauma had not occured

Clinical Care

Diagnostic procedures

Behavioral rating scales Measure of sustained attention &

impulse control Medication follow-up

Clinical Care

Behavior Rating Scales Child-Behavior Checklist (CBCL)

Parent RatingTeacher RatingItem pure scales: no item overlap

Clinical Care

Behavior Rating Scales BASC (Reynolds & Kamphaus)

Ages 2 - 18Item pure scales: no item overlapeasy to administershorter: about 140 items

Clinical Care


2-6: parent/other ratings7-12: self rating

parent rating teacher rating student observation guide

Clinical Care


13-18: self parent

teacher student observation guide

Clinical Care


New: ADHD predictorderived from discriminant function analysis using best predictors

Clinical Care

Behavior Rating Scales Parent Ratings generally show more

impairment for child than do Teacher Ratings

May want to use “blind” ratings from Teacher - where Teacher is unaware of use of medication

helpful with treatment follow up studies

Clinical Care IssuesTreatment Issues

Treatment consistent with theoretical models for ADHD?

NIMH Treatment GuidelinesMedication effective, data indicated

medication alone more effective than• Medication & behavioral treatment• Behavioral treatment alone• Other modalities

Clinical Care IssuesBehavioral therapies

Treatment goal: improve/increase inhibition Treatment strategies must be consistent

with goalTreatment strategies must be incorporated

into family system• Often source of increase problems if family not

stable• Noncompliance by parents

Clinical Care IssuesNewer treatment modalities

NeurofeedbackIssues:standardization of treatmentLength of treatmentTreatment cessation: maintenance of gains

Clinical CareTreatment considerations

Stimulant medication is standard of care NIMH revenue of ADHD studies

suggested thatStimulant medication alone better

than stimulant medication and behavioral therapy, behavioral therapy alone or placebo.


Medicationsmethylphenidate hydrochloride

• Ritalin• Sustained Release• Concerta

Amphetamines• Adderall• Dexedrine


Medication Issueskg/mg - is this an appropriate method for

titration?• Titration to cognitive measures produces an

overall lower mean dosage than for behavioral measures

b.i.d. or t.i.d. • Dosage?• Time of day?


Behavioral Treatmenthome and classroom based

intervention strategiesrequires cooperation of parents &

teacherseffective - but best when used with

medication


Family TherapiesFamily system with behavioral interventions

for childDoes require intact family system

Clinical Care IssuesSummary: treatment goals and plans

need to be consistent with theoretical models of ADHD

Medication: ritalin, adderall, others

Continuous performance tests

Grew out of need to provide for a measurement of attention and impulse control

Wanted actual measurement not behavioral attributes

Advances in electronics provided format Historically, measures of sustained

attention are intrical to the history of psychology

Study cited as the basis for the origin of cpts is: Rosvold, Mirsky, Sarason, Bransome & Beck (1956). A continuous performance test of brain damage. Journal of Consulting Psychology, 20, 3343-350.

Background & History

For the Rosvold et al study (1956) the purpose was to study vigilance.

The designed task was for a letter to appear one at a time using a fixed rate of presentation (ISI) at 920 ms.

Press the lever whenever the letter x appeared

Background & History

The subject also had another task - to inhibit responding when any other letter appeared.

Task became known as the X type cptRosvold et al (1956) also reported use

of a second type cpt: the AX-typeFor this task, the subject was to press

the lever if a letter A preceded the letter X

Continuous Performance Tests

Still needed to inhibit actionAuthors found the task to adequately

classify 84.2% to 89.5% of younger subjects who had brain damage

Greater classification was for AX-type

Continuous Performance TestsSince this study - have been

literally hundreds of studies utilizing a cpt task of some sort- also report Riccio,Reynolds & Lowe (2001) over 400 articles using cpts

Riccio et al (2001) reported finding 162 research studies using some form of group comparison with children and some sort of cpt task


Research studies may use a cpt designed only for that study lacking normative development increased difficulty with study

replicationEasy to program (if you find

programming easy)Many variations of design


Cpt variations stimulus presentation interval of stimulus stimulus modality distraction modes adaptive cpts length of task target/nontarget ratio

Variations of CPTsStimulus Presentation

X- type (easier task) AX- type (more difficult task) XX-type Numeric (variation of X or AX type)

GDS uses numeric stimulus1 - 9 type task (number 1 followed by

number 9)

Variations of CPTsInterstimulus Interval (ISI) variations

Rosvold et al (1956) used 920 ms some have used from 50 to 1500 ms

(Friedman, Vaughan & Erlenmeyer-Kimling (1981)

500 to 1500 ms (Schachar, Logan, Wachsmuth & Chajczyk, 1988)

some tasks maintain consistent ISI others use variable ISI within task

Variations of CPTsOther component related to ISI is that

of stimulus onset asynchrony (SOA)This refers to the onset of the stimulus

followed by the onset of the next stimulus

i.d., stimulus may “linger” longer allowing task recognition

some cpts use variable SOA, others consistent SOA

Variations of CPTsISI - SOA

increase ISI decrease SOAshorter SOA may increase “mis-hits” shorter SOA may increase omissions

increase ISI increase SOAslower response times

Variations of CPTsStimulus Modality (Visual/Auditory)

Non-alphanumeric Square within square (T.O.V.A.)Rabbit (in development)

Auditory stimulus presentation modelsauditory X or AX typesauditory numerictones (T.O.V.A.-A.)

Variations of CPTsDistraction

these cpts use X or AX-type then add another dimension: interference or distraction

goal is to increase level of difficulty distraction task varies by cpt

degraded or blurredvisual distractions common for visual X or AX cptsauditory distractions

Variations of CPTsAdaptive cpts

increase level of difficulty as success of task accomplished and maintained

Variations of CPTsLength of task

Bremer (1989) reported “mini-cpt”3 minute task6 minute task available

T.O.V.A./T.O.V.A.-Alongest21.6 minutes

Variations of CPTsTarget/nontarget ratio

refers to presentation of targets to nontargets throughout task

some use variable others consistent some use variable mixed with variable

ISI

CommentsInfluences on cpt performance

directions examiner presence anxiety, depression and the rest of

DSM-IV drugs and alcohol (including caffeine) environmental distractions

The Big 44 major cpts have emerged within the

marketplaceall report normative and

standardizationAlphabetical order:

Conners’ CPT (“The cpt”??) GDS IVA T.O.V.A./T.O.V.A.-A.

The Big 4Conners’ CPT

Available from Multihealth Systems, Inc (MHS)*

www.mhs.com 800.456.3033

* may be available from other distributors such as PAR or WPS

The Big 4Conners’CPT

Type: not x Modality: Visual Stimulus display 250 ms ISI varied 1000 to

4000 ms (varied

within block)


Target Letter Length 14 minutes Nontargets letters Distraction none Target ratio not varied


Block Timing yes Customized available Examiner presence ? Practice trials yes Standardized instructions yes

The Big 4Conners’ CPT Scoring

correct hits omission/commission errors d-prime/beta reaction time reaction time standard deviation

The Big 4Conners’CPT Scoring

slope of standard error slope at ISI change slope of standard error at ISI change overall performance index

The Big 4GDS: Gordon Diagnostic System

Available from: Gordon Systems, Inc.*

www.gsi.com 800.550.2343

* note: may be available from other distributors such as PAR, WPS

The Big 4GDS

Type AX(numeric) Modality Visual Stimulus display 200 ms ISI 1000/2000 ms

(children adults/preschool)

The Big 4GDS

Target number Length 9 minutes/6 for preschool Nontargets numbers Distraction yes Target ratio not varied

The Big 4GDS

Block Timing yes Customized

available Examiner presence yes Practice trials yes

The Big 4GDS Scoring

correct hits omission/commission errors reaction time target related error / random error

The Big 4Intermediate Visual and Auditory CPT

(IVA) also known as Integrated Visual & Auditory CPT Available from: BrainTrain*

www.braintrain-online.com 804.320.0105

* Note: May also be available from other distributors such as PAR, WPS

The Big 4IVA

Type X Modality Visual & auditory in same

task Stimulus Display 167 auditory/500

visual ISI 1500 ms

The Big 4IVA

Target number Length 13 Nontargets numbers Distraction no? Target ratio varied

The Big 4IVA

Block Timing yes Customized no Examiner presence yes Practice trials yes

The Big 4IVA Scoring

response control quotient (auditory,visual, full)

attention quotient (auditory, visual, full) auditory & visual prudence scores vigilance consistency stamina


focus speed balance persistence fine motor/hyperactivity


sensoriomotor readiness comprehension

The Big 4Test of Variables of Attention

(T.O.V.A.) & Test of Variables of Attention-Auditory (T.O.V.A.-A.) Available from: Universal Attention

Disorders, Inc. www.tovatest.com 800.729.2886 (800-PAY-ATTN)

*Note: Also available from other distributors such as PAR, WPS

The Big 4T.O.V.A./T.O.V.A.-A.

Type: X Modality: Visual/Auditory Stimulus display 100 ms ISI 2000 ms


Target position of square

Length 21.6 mins Nontargets position of square Distraction no Target ratio varied


Block Timing yes Customized yes Examiner presences yes Practice trials yes

The Big 4T.O.V.A./T.O.V.A.-A. Scoring

omission/commission errors response time response time variability d prime

The Big 4T.O.V.A./T.O.V.A.-A. Scoring

multiple responses anticipatory Responses ADHD scale post commission error response time

T.O.V.A.Non-language based stimulusX-typeSquare within square stimulusSquare at top – targetSquare at bottom - nontarget

T.O.V.A.T.O.V.A.-A. uses two tones:

Middle c: non-target G above middle C: target

Consistent with paradigm: top is the target

T.O.V.A.Standardized instructions: to be

given in language appropriate for subject (native)

Examiner must be present: standardization group did have examiner present

Prompt for subject to respond as quickly as possible when sees target

T.O.V.A.Separate standardization samplesOver 2500 subjects in T.O.V.A.-A.

Age 6 & above Ages 19-30

Over 2000 subjects in T.O.V.A. Age 4-5: 11.3 minute version One quarter of target frequent/infrequent

T.O.V.A.T.O.V.A.

One year age increments ages 6 to 19 Data by gender Ages 20 & above: by decade Data by gender

T.O.V.A.Two conditions: target infrequent &

target frequent3.5:1 non-targets for every target

(infrequent)3.5:1 targets for every non-target:

(frequent)Stimuli presented in a fixed random

model

T.O.V.A.Quarter 1 & 2: target infrequent

Subject who is inattentive likely to miss target

Measure of attention Omission errors likely

Quarter 3 & 4: target frequent Subject who is impulsive likely to “mis-hit” Measure of impulse control Commission errors likely

T.O.V.A.Scores presented by quarters, halves

& total for each variableScoring uses derived standard

scores, 100 mean, 15 standard deviation

Higher scores reflect better performance, lower scores reflect poorer performance

T.O.V.A.In addition:

Z scores Percentiles for RT & RTV

Anticipatory errors Responses presented from 200 ms prior

to stimulus onset to 200 ms after onset

T.O.V.A.Multiple Responses: pressing button

more than once Post-Commission Response Time:

following commission error, response time for next correct target identification is recorded

T.O.V.A.Multiple responses rare in

standardization group Increased multiple responses decrease

validity of subject performanceError Analysis: examiner is able to

review all responses to all stimuli over duration of test

T.O.V.A.ADHD score

Based upon ROC discriminant function analysis

Best 3 predictors for placing subjects in ADHD prediction group

Uses subject z scores

T.O.V.A.ADHD score

Scores less than or equal to zero (0) indicate subject more likely to be placed in ADHD group

Scores above zero (0) indicates subjects less likely to be placed in ADHD group

NOTE: RECALL THAT Z SCORES ARE USED TO DERIVE SCORES

T.O.V.A.D Prime

Measure of performance consistency over duration of task

Beta: not found to be significant between groups, thus is not reported

T.O.V.A.Construct validity

Actual Predicted Normal ADHD

Normal 75% 25%ADHD 23% 77%

Leark, R.A., Dixon, D., Llorentes, A., Allen, M. (2000) Cross-validation & Performance Discriminant Abilities of the T.O.V.A. using DSM-IV criteria. Poster presentation at the 20th Annual Meeting of the National Academy of Neuropsychology. Orlando, FL.

T.O.V.A.Sensitive to malingering

Increased errors across all 4 quarters, both halves and total score for omission & commission

Decreased response time Increased variability of response time

Leark, R.A., Dixon, D., Hoffman, T. & Hunyh, D.(in press). Effects of Fake Bad performance on the T.O.V.A. Archives of Clinical Neuropsychology

T.O.V.A.Relationship to IQ

Greenberg has reported need to adjust T.O.V.A. scores for IQ

HOWEVER – Research has indicated this to be a false assumption

T.O.V.A.Chae (1999)

T.O.V.A. not found to be significantly correlated with VIQ/PIQ/FSIQ

PIQ/FSIQ is moderately related to Omission total scores ( .46 & .44)

Picture Arrangement & Object Assembly correlated at -.50 & -.54

T.O.V.A.Chae (1999)

Freedom from Distractibility factor not significantly correlated

Processing Speed factor not significantly correlated

T.O.V.A.Other studies have reported similar

findings At best there is approximately a .50

correlation between FSIQ and T.O.V.A. scores

Third factor not significantly correlated with T.O.V.A. scores

IQ not factor in T.O.V.A. performance

T.O.V.A.Construct validity for T.O.V.A.-A

ADHD (DSM-IV) to normal control children Diagnosis independent of T.O.V.A.-A.

performanceAll subjects correctly classified using z

scoresLeark, R.A., Golden, C.J., Escalande, A. & Allen, M. (2001) Initial

Dicriminant Abilities of the T.O.V.A.-A. Poster paper presented at the 21st Annual Meeting of the National Academy of Neuropsychology

T.O.V.A.Temporal Stability of T.O.V.A.

Internal coefficients not appropriate for timed tasks

Temporal stability: reasonable time interval90 minutes1 week

T.O.V.A.90 Minute Interval

Scale coefficientOmission 0.80Commission 0.78RT 0.93RTV 0.77

T.O.V.A.1 Week Interval

Scale Coefficient Omission 0.86 Commission 0.74 RT 0.79 RTV 0.87

T.O.V.A.

Sem Scale 90 Minute 1 Week Omission 6.71 5.61 Commission 7.04 7.65 RT 3.97 6.87 RTV 7.19 5.41

Note: reflects T-scores

T.O.V.A.Relationship to behavioral rating

scales Forbes (1998) reported that the T.O.V.A.

provided distinct information that added to increased diagnostic accuracy

Correlation studies have report significant but moderate correlations between behavioral measures and test variables

T.O.V.A.Forbes (1998)

ACTers Hyper OM -.37 COM -.30 Oppos OM -.38 COM -.25 Attn OM -.25 COM -.16

T.O.V.A.Selden, Pospisil, Michael & Golden

(2001)CBCL-TRF Attention Index

ADHD score .393TOVA-A COM .372

CPRS Hyperactivity ScaleTOVA OM .423

PIC-R Hyperactivity ScaleTOVA COM .325

T.O.V.A.

Continuous Performance Test (CPT)

measure of sustained attention & vigilance

measure of impulse control long, boring measures

T.O.V.A.

Test of Variables of Attention (Greenberg, 1992) T.O.V.A. : non-language stimulus task computer based fixed two second interstimulus interval

(ISI) 21.6 minute long task

T.O.V.A.

Nontarget Target

T.O.V.A.

two task paradigms: target infrequent & target frequent

a constant 3.5:1 ratio Target Infrequent: 3.5: 1 non-targets to

targets Target Frequent: 3.5:1 targets to non-

targets

T.O.V.A.

Internally clocked Data summarized into quarters,

halves and total scoreQuarters 1 & 2 - target infrequent Quarters 3 & 4 - target frequentHalf 1 - target infrequentHalf 2 - target frequent

T.O.V.A.

Extensive norm development: over 2300 subjects

Scaled by age and genderUses derived standard scores with

mean of 100, standard deviation of 15

z scores also provided

T.O.V.A.

T.O.V.A. Scales Omission - measure of

attention/inattention Commission - measure of impulse control Response Time - in milliseconds Response Time Variability - measure of

response consistency d’ (d prime) - signal detection measure

response consistency

T.O.V.A.

Established construct and disciminant validity

Established reliability: 90 minute, 1 week, 8 week and 12 week intervals

Established sensitivity & specificity (80/20)

T.O.V.A.

Semrud-Clikeman & Wical (1999) evaluated attentional difficulties in children

with complex partial seizures (CPS), CPS & ADHD, CPS without ADHD, and controls

used T.O.V.A. as measure of sustained attention & impulse control

Components of Attention in Children with Complex Partial Seizures with and without ADHD. Epilepsy, 40(2): 211-215.

T.O.V.A.

Semrud-Clikeman & Wical (1999) Results: Found poorest performance on the

T.O.V.A. by the CPS/ADHD group. Difficulty in attention was noted for

children with epilepsy regardless of ADHD When methylphenidate was administered

to the ADHD groups - both improved on T.O.V.A. scores

T.O.V.A.

Semrud-Clikeman & Wical (1999) Conclusions

Epilepsy may dispose children to attention problems that can significantly impair with learning

Improvement, as measured by improved T.O.V.A. measures was found for both ADHD groups when methylphenidate was administered

T.O.V.A.

Mautner, Thakkar, Kluwe & Leark (in press) NF1, NF1 with ADHD, ADHD & controls NF1 with ADHD & ADHD similar over 15% of the NF1 participants displayed

symptoms of ADHD Both the NF1 with ADHD and the ADHD

subjects had improved T.O.V.A. scores when methylphenidate was administered

Treatment of ADHD in NF1 Type 1. Developmental Medicine


Medicationsmethylphenidate hydrochloride

• Ritalin• Sustained Release• Concerta

Amphetamines• Adderall• Dexedrine


Medication Issueskg/mg - is this an appropriate method for

titration?• Titration to cognitive measures produces an

overall lower mean dosage than for behavioral measures

b.i.d. or t.i.d. • Dosage?• Time of day?


Behavioral Treatmenthome and classroom based

intervention strategiesrequires cooperation of parents &

teacherseffective - but best when used with

medication


Family TherapiesFamily system with behavioral interventions

for childDoes require intact family system

References

robert a. leark, ph.d. fellow, national academy of neuropsychology

Documents

elementspsychiatric

attentionsustaining

timeshifting of attention

deficientsustained attention

factor model

optimal arousal alertness

model similar

multiple components