Introduction to
Physiological Psychology
Psych 260
Kim Sweeney
ksweeney@cogsci.ucsd.edu
www.cogsci.ucsd.edu/~ksweeney/Psych260
Visual Agnosia
Deficits in visual form perception
NOT blindness!
Caused by damage to visual association
areas in ventral stream
Video….
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Fusiform Face Area
The fusiform face
area (FFA) is part of
the ventral (“what”)
pathway. It’s located
on the ventral
surface of the
temporal lobe.
Prosopagnosia
Damage to the fusiform face area (FFA)
results in prosopagnosia.
Diffusion tensor imaging (DTI) tractography reveals a reduction in the volume
of the inferior longitudinal fasciculus in the brains of 6 patients with
congenital prosopagnosia (top). (From Thomas et al 2008)
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The lateral occipital complex is activated in
response to a wide variety of objects.
It seems possible that different categories of
objects are processed at least in part in
different subregions
subregions..
Fusiform Face
Area (FFA)
Parahippocampal
Place Area (PPA)
Kanwisher et al (97-99)
Tong et al (in press)
Sergent et al (92)
Haxby et al (91, 94, 99)
Puce et al (95, 96)
McCarthy et al (97)
Halgren et al (99)
Epstein & Kanwisher (98)
Aquirre et al (98, 99)
Haxby et al (99)
Maguire et al (96, 97, 98)
LOC: Things
Malach et al. (95)
Kanwisher et al. (96)
Grill-Spector et al (98, 99)
Kourtzi & Kanwisher (00)
Body Area
Downing et al (01)
Drawing Modified from Allison et al (94)
Also in the ventral stream is the
extrastriate body area
– Seems to be particularly responsive to body
parts
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The Auditory System
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What is sound?
If a tree falls in a forest and no one is
there to hear it, would there be a sound?
What is sound?
If a tree falls in a forest and no one is
there to hear it, would there be a sound?
SOUND can refer to a physical stimulus or
a perceptual response.
– Physical stimulus: “sound” is pressure
changes in air (or other medium)
– Perceptual response: “sound” is the
experience we have when we hear
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What is sound?
Auditory perception occurs when sound
waves interact with the structures of the
ear.
Sound Wave—changes over time in the
pressure of an elastic medium (e.g., air or
water)
– Without air (or another elastic medium), there can
be no sound waves, and thus no sound.
What is “color”?
Hue – determined by wave
length (red= longer, violet =
shorter)
Brightness – determined by
amplitude
Saturation – determined by
purity
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What is “sound”?
Pitch- determined by the frequency of a
Pitchvibration
Loudness- determined by the amplitude
Loudness(intensity) of a vibration
Timbre- determined by the complexity of
Timbrea vibration
Frequency of Sound Waves
The frequency of a sound wave is
measured as the number of cycles
per second (Hertz):
20,000 Hz
4,186 Hz
1,000 Hz
100 Hz
27 Hz
Highest Frequency we can hear
Highest note on a piano
Highest pitch of human voice
Lowest pitch of human voice
Lowest note on a piano
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Different animals are sensitive to
different frequency ranges
From Dusenbery, 1994
Intensity of Various Sounds (dB)
Log P Decibels
Softest detectable sound
0
Soft whisper
20
Quiet neighborhood
40
Average conversation
60
Loud music from a radio
80
Heavy automobile traffic
100
Very loud thunder
120
Jet airplane taking off
140
Loudest rock band on record
160
Spacecraft launch (from 150 ft.)
180
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Timbre of various sounds
Sound as a physical stimulus
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Sound as a psychological experience
Amplitude of a sound wave is related to loudness of a sound.
Frequency of a sound wave is related to the pitch of a sound.
Complexity of a sound wave is related to the timbre of a sound.
sound.
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What is “sound”?
The relation between the physical and perceptual dimensions of sound
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But how do we hear sound?
Purpose of the structures in the ear:
– Measure the frequency (pitch) of sound waves
– Measure the amplitude (loudness) of sound waves
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Major Structures of the Ear
Outer ear (Pinna
(Pinna))—acts as a funnel to
direct sound waves towards the tympanic
membrane and inner ear structures
Middle ear—
ear—consists of three small bones
(or ossicles)
ossicles) that amplify the sound
Inner ear—
ear—contains the structures that
actually transduce sound into neural
response
Anatomy of the Ear
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Audition in three easy steps
Sound is funneled via the pinna (external ear)
through the ear canal to the tympanic membrane
(eardrum), which vibrates with the sound
The middle ear (located behind the tympanic
membrane) includes the middle ear bones, the
ossicles (malleus
malleus,, incus and stapes)
The malleus connects with the tympanic membrane
and transmits vibrations via the incus and stapes (at
the oval window) to the cochlea (inner ear), the
structure that contains the receptors
The Ear
Sound wave > eardrum > ossicles > oval window
Vibration of the oval window sets in motion the
fluid of the cochlea
The cochlea’s internal membrane, the organ of
Corti,, is the auditory receptor organ
Corti
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The Cochlea
The cochlea is part of the inner ear; it is filled with fluid,
therefore sounds transferred through the air must be
transferred into a liquid medium; the ossicles aid in this
transmission
Within the cochlea,
there are three
separate chambers:
Scala vestibuli
Scala media
Scala tympani
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The Cochlea
The organ of Corti is found in the middle
chamber- scala media
The organ of Corti consists of
– Basilar membrane (the base)
– Tectorial membrane (the roof)
– Hair cells in between
Hair cells within the organ of
Corti transduce sound waves
into nerve impulses
– Inner hair cells are crucial for hearing, outer hair
cells enhance inner hair cells’ sensitivity
Hair Cells, or Cilia
In the human cochlea
we find TWO kinds of
hair cells:
Inner hair cells
– Responsible for hearing
(95% of afferent info)
Outer hair cells
– Responsible for
amplifying soundsound- they
can move, so amplify
basilar membrane
movement
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Auditory Hair Cells
Inner hair cells: (~ 3500)
form a single line of cells along
the basilar membrane
Destruction of inner hair cells
eliminates hearing
Outer hair cells: (~ 12,000)
are arranged in three rows
along the basilar membrane
Outer hair cells serve a
structural function
The cilia project from the top of each hair cell
The tectorial membrane is attached to the
(some of the) outer hair cell cilia
When sound waves move the basilar and
tectorial membranes, the cilia bend in one
direction or the other
Shear of the cilia generates a receptor
potential that releases a neurotransmitter
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The Basilar Membrane
Sound waves cause the basilar membrane
to move relative to the tectorial
membrane, which bends the cilia of the
hair cells…
this bending produces
receptor potentials!!
Because of the
physical properties
of basilar membrane:
tonotopic organization
Cilia are connected by tip links
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Auditory Transduction
Cilia tips are joined by
fiber links
Cilia movement
produces tension of
the link which opens
(or closes) ion
channels in the
adjacent tip
Calcium and potassium
ions produce a
depolarization or
hyperpolarization
7.37
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Auditory Transduction
Movement towards
the tallest cilium
result in
depolarization:
– Higher firing rate
Movement away
from the tallest
cilium results in
hyperpolarization:
– Lower firing rate
Sound Transmission Through the Ear
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Sound Transmission Through the Ear
Sound Transmission Through the Ear
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Sound Transmission Through the Ear
Sound Transmission Through the Ear
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Cochlear Coding
Different frequencies produce maximal
stimulation of hair cells at different
points along the basilar membrane
Tonotopic (frequency) organization exists
not only at the basilar membrane but also
in most other parts of auditory system
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Tonotopic OrganizationOrganization- Place Coding
Tonotopic Organization
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Distinguishing Pitch
Place theory—
theory—different frequencies cause
larger vibrations at different locations
along the basilar membrane (place coding)
Frequency theory—
theory—basilar membrane
vibrates at the same frequency as the
sound wave (rate coding)
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Pitch perception:
Place coding
The cochlea has a
tonotopic organization
For high frequencies
Pitch Perception: Rate code
Used for low frequency sounds ( <1500 Hz )
Mechanism: The rate of neural firing matches
the sound's frequency. For example,
– 50 Hz tone (50 cycles per sec) -> 50 spikes/sec,
– 100 hz -> 100 spikes/sec
Problem: even at the low frequency range,
Problem:
some frequencies exceed neurons’ highest
firing rate (200 times per sec)
Solution:: large numbers of neurons that are
Solution
phased locked (volley principle).
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Then what?
Sound is
processed both
ipsilaterally and
(especially)
contralaterally
Then what?
Cochlear nerve>
cochlear nucleus of medulla >
superior olive >
inferior colliculus>
colliculus>
MGN (thalamus!) >
Primary auditory cortex
Efferent information from
inferior colliculus
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Subcortical Mechanisms of
Sound Localization
The lateral and medial superior olives react to
differences in what is heard by the two ears
– Medial – arrival time differences
– Lateral – amplitude differences
Both project to the superior colliculus
– The deep layers of the superior colliculus are laid out
according to auditory space, allowing location of sound
sources in the world; the shallow layers are laid out
retinotopically
– … so it seems that function is identifying location
Anatomy and function
Many
sound features are encoded before
the signal reaches the cortex
- Cochlear nucleus segregates
sound information
- Signals from each ear converge on
the superior olivary complex important for sound localization
- Inferior colliculus is sensitive to
location, absolute intensity, rates of
intensity change, frequency important for pattern categorization
- Descending cortical influences
modify the input from the medial
geniculate nucleus - important as
an adaptive ‘filter’
cortex
medial geniculate
body
inferior colliculus
cochlear nucleus
complex
cochlea
superior olivary complex
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Sound Localization
Interaural Intensity Difference (high
frequency)
Interaural Time Difference (low
frequency)
Spatial Location of Sound
Auditory neurons in the superior olives
detect phase differences
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Perception of Spatial Location
Arrival time difference for high frequency sound
“What” and “Where” pathways
Just as in the visual system, the auditory
system seems to have separate pathways
for analyzing the location and the
identity of a sound.
Just as in the visual system, the “where”
pathway is more dorsal, and the “what”
pathway is more ventral.
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Evidence for “top“top-down”
processing in the auditory system
Next time…
– The vestibular system
– Gustation and Olfaction
– !! Somatosenses AFTER all this other stuff!
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