Psychology 210Psychology 210

Lecture 5Lecture 5

Kevin R SmithKevin R Smith

TodayToday

The Auditory systemThe Auditory system The Somatosensory systemThe Somatosensory system The chemical systemsThe chemical systems

Properties of soundsProperties of sounds

Sounds are wavesSounds are waves• Amplitude: Amplitude:

loudnessloudness• Frequency: pitchFrequency: pitch

Audible SoundAudible Sound

The earThe ear

The earThe ear Outer earOuter ear

• PinnaPinna• Auditory canalAuditory canal

Anatomy of the earAnatomy of the ear

Middle earMiddle ear• Tympanic Tympanic

membrane: Ear membrane: Ear drumdrum

• OsciclesOscicles Malleus (Hammer)Malleus (Hammer) Incus (Anvil)Incus (Anvil) Stapes (Stirrup)Stapes (Stirrup)

• Oval WindowOval Window

Anatomy of the earAnatomy of the ear

Inner earInner ear• Semicircular canalsSemicircular canals• CochleaCochlea

Basilar membraneBasilar membrane• Hair cellsHair cells

The basilar membraneThe basilar membrane Hair cells translate Hair cells translate

vibrations from vibrations from the sound waves the sound waves into frequenciesinto frequencies

Higher pitches are Higher pitches are processed closer processed closer to the baseto the base

Lower pitches are Lower pitches are processed closer processed closer to the apexto the apex• Tonotopic Tonotopic

organizationorganization

TransductionTransduction

The hair cells moveThe hair cells move• Opens Ca channelsOpens Ca channels• Leads to the perception of a signalLeads to the perception of a signal• Different hair cells move depending on the Different hair cells move depending on the

frequency of the incoming soundfrequency of the incoming sound

Hair cellsHair cells Hair cell damageHair cell damage

• Noise, infections, genetic diseases, agingNoise, infections, genetic diseases, aging• Higher frequencies are harder to hear as you Higher frequencies are harder to hear as you

ageage RegenerationRegeneration

• Can occur in birds and some invertebratesCan occur in birds and some invertebrates• Generally does not occur in humansGenerally does not occur in humans

The Pathway to the brainThe Pathway to the brain

The auditory nerveThe auditory nerve Cochlear nucleusCochlear nucleus Superior olivary Superior olivary

nucleusnucleus The inferior The inferior

colliculuscolliculus Thalamus (medial Thalamus (medial

geniculate nucleus)geniculate nucleus) Primary auditory Primary auditory

cortexcortex

In the superior olivary nucleusIn the superior olivary nucleus

Information from the ears is first Information from the ears is first combined herecombined here

May have some role in localization of May have some role in localization of soundssounds

Tonotopically organizedTonotopically organized

Organization of the MGNOrganization of the MGN

Similar to the LGN for visionSimilar to the LGN for vision Different layers have different inputsDifferent layers have different inputs Tuning curves become more specificTuning curves become more specific Tonotopically organizedTonotopically organized

Organization of A1Organization of A1

Tonotopically Tonotopically organizedorganized

Just like the Just like the cochlea, superior cochlea, superior olivary nucleus, olivary nucleus, and MGN, different and MGN, different tones are tones are processed in processed in different locationsdifferent locations

After A1After A1

Like vision: A2, A3, A4…Like vision: A2, A3, A4… Two pathwaysTwo pathways

• Dorsal “where” pathwayDorsal “where” pathway• Ventral “what” pathwayVentral “what” pathway

Researchers try and relate auditory systems Researchers try and relate auditory systems to visual systemsto visual systems

Some similarities have been found, but Some similarities have been found, but nothing is certainnothing is certain

Is the auditory system Is the auditory system contralaterally organized?contralaterally organized?

SomewhatSomewhat 80% of incoming information into 80% of incoming information into

each auditory cortex is from the each auditory cortex is from the contralateral ear and 20% is from the contralateral ear and 20% is from the ipsilateral earipsilateral ear

Why the combining of the incoming Why the combining of the incoming information from the two ears?information from the two ears?

Spatial cuesSpatial cues

We need information from both ears We need information from both ears to locate where a sound is in spaceto locate where a sound is in space

Two main cuesTwo main cues• Interaural intensity (level) difference (IID Interaural intensity (level) difference (IID

or ILD)or ILD)• Interaural time difference (ITD)Interaural time difference (ITD)

Also our pinna provides information Also our pinna provides information about how vertical a sound isabout how vertical a sound is

Interaural Intensity DifferencesInteraural Intensity Differences

The ear that is closer to the sound The ear that is closer to the sound hears a louder sound than the ear that hears a louder sound than the ear that is farther from the soundis farther from the sound

The difference in loudness here is a The difference in loudness here is a difference in intensitydifference in intensity

Our head provides a shadow effect Our head provides a shadow effect over the far earover the far ear

Based upon the difference in intensity, Based upon the difference in intensity, our brain can calculate where the our brain can calculate where the sound wassound was

Interaural Time DifferencesInteraural Time Differences The ear that is closer to the sound hears the The ear that is closer to the sound hears the

sound earlier than the ear that is farther sound earlier than the ear that is farther from the soundfrom the sound

Based upon the difference in time, our brain Based upon the difference in time, our brain can calculate where in space the sound wascan calculate where in space the sound was

IIDs and ITDsIIDs and ITDs

IIDs and ITDsIIDs and ITDs

Only provide Only provide information about information about where a sound is where a sound is along the along the horizontalhorizontal

We use our pinnas We use our pinnas to locate where a to locate where a sound is verticallysound is vertically• Head related Head related

transfer functionstransfer functions

Interesting NoteInteresting Note

Changing the Changing the shape of the pinna shape of the pinna change localization change localization abilitiesabilities

Eventually subjects Eventually subjects learn to localize learn to localize sounds properlysounds properly

The somatosensory systemThe somatosensory system

The Vestibular SystemThe Vestibular System TouchTouch TemperatureTemperature PainPain

The Vestibular SystemThe Vestibular System Fluid filled Fluid filled

cavatiescavaties Semicircular Semicircular

canalscanals OtolithsOtoliths

• SacculeSaccule• UtricleUtricle

Found near the Found near the ear and auditory ear and auditory structuresstructures

How the vestibular system worksHow the vestibular system works

Fluid filled cavitiesFluid filled cavities Contain hair cellsContain hair cells

• Sensitive to direction of movementSensitive to direction of movement• Either hyperpolarize or depolarizeEither hyperpolarize or depolarize• Provide information about the location in Provide information about the location in

space of the headspace of the head Semicircular canalsSemicircular canals

• Provide more information about the Provide more information about the rotation of the headrotation of the head

How the vestibular system worksHow the vestibular system works

Pathway to the brainPathway to the brain

Auditory nerveAuditory nerve Pons, medulla, cerebellumPons, medulla, cerebellum

• Vestibular nucleiVestibular nuclei Ventral posterior thalamusVentral posterior thalamus Primary somatosensory cortex and Primary somatosensory cortex and

primary motor cortexprimary motor cortex

The vestibular systemThe vestibular system

Information is highly integrated with Information is highly integrated with information from the visual cortexinformation from the visual cortex

Also, projects to the spinal cord for Also, projects to the spinal cord for feedback regarding posturefeedback regarding posture

TouchTouch

The Sensory inputsThe Sensory inputs• Meissner’s Meissner’s

corpusclescorpuscles• Pacinian corpusclesPacinian corpuscles• Merkel’s disksMerkel’s disks• Ruffini’s endingsRuffini’s endings• Free nerve Free nerve

distributionsdistributions• Hair follicle Hair follicle

receptorsreceptors

Differences between receptorsDifferences between receptors

Size of receptive fieldSize of receptive field• SmallSmall

Meissner’s corpusclesMeissner’s corpuscles Merkel’s disksMerkel’s disks

• LargeLarge Pacinian corpusclesPacinian corpuscles Ruffini’s endingsRuffini’s endings

Differences between receptorsDifferences between receptors

Rate of adaptationRate of adaptation• FastFast

Meissner’s corpusclesMeissner’s corpuscles Pacinian corpusclesPacinian corpuscles

• SlowSlow Merkel’s disksMerkel’s disks Ruffini’s endingsRuffini’s endings

Differences between receptorsDifferences between receptors

LocationLocation• Shallow in the skinShallow in the skin

Meissner’s corpuscles Meissner’s corpuscles Merkel’s disksMerkel’s disks

• Deep in the skin (digestive tracts, joints)Deep in the skin (digestive tracts, joints) Pacinian corpusclesPacinian corpuscles Ruffini’s endingsRuffini’s endings

Differences between receptorsDifferences between receptors

Type of information processedType of information processed• PressurePressure

Meissner’s corpusclesMeissner’s corpuscles Merkel’s disksMerkel’s disks

• Pressure and vibrationsPressure and vibrations Pacinian corpusclesPacinian corpuscles

• StretchStretch Ruffini’s endingsRuffini’s endings

• Pain and temperaturePain and temperature Free nerve endingsFree nerve endings

Meissner’s CorpusclesMeissner’s Corpuscles

Pacinian corpusclesPacinian corpuscles

Pathway to the brainPathway to the brain

Spinal cordSpinal cord Medial lemniscusMedial lemniscus Ventral posterior nucleus of the Ventral posterior nucleus of the

thalamusthalamus S1S1

Organization of S1Organization of S1 Somatotopically Somatotopically

organizedorganized Cortical magnificationCortical magnification The amount of cortex The amount of cortex

devoted to your hand devoted to your hand is more than the is more than the amount of cortex amount of cortex devoted to your torso, devoted to your torso, even though your even though your torso is largertorso is larger

Why?Why?

SomatotopySomatotopy

Your hand is much Your hand is much more sensitive to more sensitive to touch than your touch than your backback

Same with face, Same with face, mouth, eyes, etc…mouth, eyes, etc…

HomunculusHomunculus

Other types of receptorsOther types of receptors Free Nerve Ending ReceptorsFree Nerve Ending Receptors

• ThermoreceptorsThermoreceptors Respond to warmth or coldRespond to warmth or cold

• NociceptorsNociceptors Respond to mechanical pain, extreme heat, or bothRespond to mechanical pain, extreme heat, or both

The chemical sensesThe chemical senses

Senses that use chemical receptorsSenses that use chemical receptors• Olfaction: SmellOlfaction: Smell

Olfactory epithelium detects molecules in Olfactory epithelium detects molecules in the airthe air

• TasteTaste Saliva dissolves food into moleculesSaliva dissolves food into molecules

Smelling…..Smelling…..

1000 different smell receptors1000 different smell receptors Each receptor detects a broad range Each receptor detects a broad range

of smellsof smells Based upon the combination of Based upon the combination of

activity from the receptors, our brain activity from the receptors, our brain constructs the smellconstructs the smell

The olfactory systemThe olfactory system

The noseThe nose• Olfactory Olfactory

epitheliumepithelium• Olfactory Olfactory

receptor cells receptor cells synapse onto synapse onto olfactory nerves olfactory nerves within the within the olfactory bulbolfactory bulb

The olfactory systemThe olfactory system

Pathway to the brainPathway to the brain• Olfactory bulb axons form the olfactory Olfactory bulb axons form the olfactory

tracttract• Olfactory cortexOlfactory cortex• Thalamus: Medial dorsal nucleus Thalamus: Medial dorsal nucleus • Projects to all over the brainProjects to all over the brain

Various frontal areasVarious frontal areas

TasteTaste

The tongueThe tongue• Four different taste buds Four different taste buds

Sweet, sour, salty, bitterSweet, sour, salty, bitter Umami: savoryUmami: savory

• Possibly a fifth type of taste budPossibly a fifth type of taste bud

PapillaPapilla• Bumps on the tongueBumps on the tongue• Each contains up to 100 taste budsEach contains up to 100 taste buds

The TongueThe Tongue

Pathway to the brainPathway to the brain Tongue: taste fibers – cranial nerves –Tongue: taste fibers – cranial nerves –

Thalamus: ventral posterior medial Thalamus: ventral posterior medial nucleus – parietal lobenucleus – parietal lobe