Psychology 210 Lecture 5 Kevin R Smith

Today The Auditory system The Auditory system The Somatosensory system The Somatosensory system The chemical systems The chemical systems

Properties of sounds Sounds are waves Sounds are waves Amplitude: loudnessAmplitude: loudness Frequency: pitchFrequency: pitch

Audible Sound

The ear

Outer ear Outer ear PinnaPinna Auditory canalAuditory canal

Anatomy of the ear Middle ear Middle ear Tympanic membrane: Ear drumTympanic membrane: Ear drum OsciclesOscicles Malleus (Hammer) Malleus (Hammer) Incus (Anvil) Incus (Anvil) Stapes (Stirrup) Stapes (Stirrup) Oval WindowOval Window

Anatomy of the ear Inner ear Inner ear Semicircular canalsSemicircular canals CochleaCochlea Basilar membrane Basilar membrane Hair cellsHair cells

The basilar membrane Hair cells translate vibrations from the sound waves into frequencies Hair cells translate vibrations from the sound waves into frequencies Higher pitches are processed closer to the base Higher pitches are processed closer to the base Lower pitches are processed closer to the apex Lower pitches are processed closer to the apex Tonotopic organizationTonotopic organization

Transduction The hair cells move The 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 frequency of the incoming soundDifferent hair cells move depending on the frequency of the incoming sound

Hair cells Hair cell damage Hair cell damage Noise, infections, genetic diseases, agingNoise, infections, genetic diseases, aging Higher frequencies are harder to hear as you ageHigher frequencies are harder to hear as you age Regeneration Regeneration 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 brain The auditory nerve The auditory nerve Cochlear nucleus Cochlear nucleus Superior olivary nucleus Superior olivary nucleus The inferior colliculus The inferior colliculus Thalamus (medial geniculate nucleus) Thalamus (medial geniculate nucleus) Primary auditory cortex Primary auditory cortex

In the superior olivary nucleus Information from the ears is first combined here Information from the ears is first combined here May have some role in localization of sounds May have some role in localization of sounds Tonotopically organized Tonotopically organized

Organization of the MGN Similar to the LGN for vision Similar to the LGN for vision Different layers have different inputs Different layers have different inputs Tuning curves become more specific Tuning curves become more specific Tonotopically organized Tonotopically organized

Organization of A1 Tonotopically organized Tonotopically organized Just like the cochlea, superior olivary nucleus, and MGN, different tones are processed in different locations Just like the cochlea, superior olivary nucleus, and MGN, different tones are processed in different locations

After A1 Like vision: A2, A3, A4… Like vision: A2, A3, A4… Two pathways Two pathways Dorsal “where” pathwayDorsal “where” pathway Ventral “what” pathwayVentral “what” pathway Researchers try and relate auditory systems to visual systems Researchers try and relate auditory systems to visual systems Some similarities have been found, but nothing is certain Some similarities have been found, but nothing is certain

Is the auditory system contralaterally organized? Somewhat Somewhat 80% of incoming information into each auditory cortex is from the contralateral ear and 20% is from the ipsilateral ear 80% of incoming information into each auditory cortex is from the contralateral ear and 20% is from the ipsilateral ear Why the combining of the incoming information from the two ears? Why the combining of the incoming information from the two ears?

Spatial cues We need information from both ears to locate where a sound is in space We need information from both ears to locate where a sound is in space Two main cues Two main cues Interaural intensity (level) difference (IID or ILD)Interaural intensity (level) difference (IID or ILD) Interaural time difference (ITD)Interaural time difference (ITD) Also our pinna provides information about how vertical a sound is Also our pinna provides information about how vertical a sound is

Interaural Intensity Differences The ear that is closer to the sound hears a louder sound than the ear that is farther from the sound The ear that is closer to the sound hears a louder sound than the ear that is farther from the sound The difference in loudness here is a difference in intensity The difference in loudness here is a difference in intensity Our head provides a shadow effect over the far ear Our head provides a shadow effect over the far ear Based upon the difference in intensity, our brain can calculate where the sound was Based upon the difference in intensity, our brain can calculate where the sound was

Interaural Time Differences The ear that is closer to the sound hears the sound earlier than the ear that is farther from the sound The ear that is closer to the sound hears the sound earlier than the ear that is farther from the sound Based upon the difference in time, our brain can calculate where in space the sound was Based upon the difference in time, our brain can calculate where in space the sound was

IIDs and ITDs

Only provide information about where a sound is along the horizontal Only provide information about where a sound is along the horizontal We use our pinnas to locate where a sound is vertically We use our pinnas to locate where a sound is vertically Head related transfer functionsHead related transfer functions

Interesting Note Changing the shape of the pinna change localization abilities Changing the shape of the pinna change localization abilities Eventually subjects learn to localize sounds properly Eventually subjects learn to localize sounds properly

The somatosensory system The Vestibular System The Vestibular System Touch Touch Temperature Temperature Pain Pain

The Vestibular System Fluid filled cavaties Fluid filled cavaties Semicircular canals Semicircular canals Otoliths Otoliths SacculeSaccule UtricleUtricle Found near the ear and auditory structures Found near the ear and auditory structures

How the vestibular system works Fluid filled cavities Fluid filled cavities Contain hair cells Contain hair cells Sensitive to direction of movementSensitive to direction of movement Either hyperpolarize or depolarizeEither hyperpolarize or depolarize Provide information about the location in space of the headProvide information about the location in space of the head Semicircular canals Semicircular canals Provide more information about the rotation of the headProvide more information about the rotation of the head

How the vestibular system works

Pathway to the brain Auditory nerve Auditory nerve Pons, medulla, cerebellum Pons, medulla, cerebellum Vestibular nucleiVestibular nuclei Ventral posterior thalamus Ventral posterior thalamus Primary somatosensory cortex and primary motor cortex Primary somatosensory cortex and primary motor cortex

The vestibular system Information is highly integrated with information from the visual cortex Information is highly integrated with information from the visual cortex Also, projects to the spinal cord for feedback regarding posture Also, projects to the spinal cord for feedback regarding posture

Touch The Sensory inputs The Sensory inputs Meissner’s corpusclesMeissner’s corpuscles Pacinian corpusclesPacinian corpuscles Merkel’s disksMerkel’s disks Ruffini’s endingsRuffini’s endings Free nerve distributionsFree nerve distributions Hair follicle receptorsHair follicle receptors

Differences between receptors Size of receptive field Size of receptive field SmallSmall Meissner’s corpuscles Meissner’s corpuscles Merkel’s disks Merkel’s disks LargeLarge Pacinian corpuscles Pacinian corpuscles Ruffini’s endings Ruffini’s endings

Differences between receptors Rate of adaptation Rate of adaptation FastFast Meissner’s corpuscles Meissner’s corpuscles Pacinian corpuscles Pacinian corpuscles SlowSlow Merkel’s disks Merkel’s disks Ruffini’s endings Ruffini’s endings

Differences between receptors Location Location Shallow in the skinShallow in the skin Meissner’s corpuscles Meissner’s corpuscles Merkel’s disks Merkel’s disks Deep in the skin (digestive tracts, joints)Deep in the skin (digestive tracts, joints) Pacinian corpuscles Pacinian corpuscles Ruffini’s endings Ruffini’s endings

Differences between receptors Type of information processed Type of information processed PressurePressure Meissner’s corpuscles Meissner’s corpuscles Merkel’s disks Merkel’s disks Pressure and vibrationsPressure and vibrations Pacinian corpuscles Pacinian corpuscles StretchStretch Ruffini’s endings Ruffini’s endings Pain and temperaturePain and temperature Free nerve endings Free nerve endings

Meissner’s Corpuscles

Pacinian corpuscles

Pathway to the brain Spinal cord Spinal cord Medial lemniscus Medial lemniscus Ventral posterior nucleus of the thalamus Ventral posterior nucleus of the thalamus S1 S1

Organization of S1 Somatotopically organized Somatotopically organized Cortical magnification Cortical magnification The amount of cortex devoted to your hand is more than the amount of cortex devoted to your torso, even though your torso is larger The amount of cortex devoted to your hand is more than the amount of cortex devoted to your torso, even though your torso is larger Why? Why?

Somatotopy Your hand is much more sensitive to touch than your back Your hand is much more sensitive to touch than your back Same with face, mouth, eyes, etc… Same with face, mouth, eyes, etc…

Homunculus

Other types of receptors Free Nerve Ending Receptors Free Nerve Ending Receptors ThermoreceptorsThermoreceptors Respond to warmth or cold Respond to warmth or cold NociceptorsNociceptors Respond to mechanical pain, extreme heat, or both Respond to mechanical pain, extreme heat, or both

The chemical senses Senses that use chemical receptors Senses that use chemical receptors Olfaction: SmellOlfaction: Smell Olfactory epithelium detects molecules in the air Olfactory epithelium detects molecules in the air TasteTaste Saliva dissolves food into molecules Saliva dissolves food into molecules

Smelling… different smell receptors 1000 different smell receptors Each receptor detects a broad range of smells Each receptor detects a broad range of smells Based upon the combination of activity from the receptors, our brain constructs the smell Based upon the combination of activity from the receptors, our brain constructs the smell

The olfactory system The nose The nose Olfactory epitheliumOlfactory epithelium Olfactory receptor cells synapse onto olfactory nerves within the olfactory bulbOlfactory receptor cells synapse onto olfactory nerves within the olfactory bulb

The olfactory system Pathway to the brain Pathway to the brain Olfactory bulb axons form the olfactory tractOlfactory bulb axons form the olfactory tract Olfactory cortexOlfactory cortex Thalamus: Medial dorsal nucleusThalamus: Medial dorsal nucleus Projects to all over the brainProjects to all over the brain Various frontal areas Various frontal areas

Taste The tongue The tongue Four different taste budsFour different taste buds Sweet, sour, salty, bitter Sweet, sour, salty, bitter Umami: savory Umami: savory Possibly a fifth type of taste budPossibly a fifth type of taste bud Papilla Papilla Bumps on the tongueBumps on the tongue Each contains up to 100 taste budsEach contains up to 100 taste buds

The Tongue

Pathway to the brain Tongue: taste fibers – cranial nerves – Thalamus: ventral posterior medial nucleus – parietal lobe Tongue: taste fibers – cranial nerves – Thalamus: ventral posterior medial nucleus – parietal lobe