Transcript Ear to Auditory Cortex

MECHANISMS OF
Perception
EXTEROCEPTIVE
SENSORY SYSTEMS
1.
2.
3.
4.
5.
Auditory
Somatosensory
Olfactory
Gustatory
Vision
Sensory Areas of Cortex
3 fundamentals
• Primary
• Secondary
• Association
PRIMARY SENSORY
CORTEX
• System is the area of sensory cortex that
receives most of its input directly from the
thalamic relay nuclei of that system.
Primary Visual
Cortex
Visual
Association Area
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Regions
SECONDARY SENSORY
CORTEX
• System comprises the areas of the sensory
input from the primary sensory cortex of
that system or from other areas of the
secondary sensory cortex of the same
system.
ASSOCIATION CORTEX
• Any area of cortex that receives input from
more than one sensory system.
3 MAJOR PRINCIPLES OF
THE INTERACTIONS
1. Hierarchical Organization
A system whose members can be assigned
to specific levels or ranks in relation to one
another.
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Association Cortex
Secondary Sensory Cortex
Primary Sensory Cortex
Thalamic Relay Nuclei
Receptors
NOTE:
• The hierarchical org. of sensory system is
APPARENT from comparisons of the
effects of damage to various levels:
• The higher the level the damage, the more
specific and complex the deficit.
Example:
Destruction of a sensory system’s receptors
produces a complete loss of ability to
perceive in that sensory modality (blindness
or deafness)
TWO GENERAL PHASES
OF PERCEPTION
• Sensation – the process of detecting the
presence of the stimuli.
• Perception- the higher-order process of
integrating, recognizing, and interpreting
complete patterns of perception
FUNCTIONAL
SEGREGATION
• The functions is distinct that specialized
different kinds analysis.
PARALLEL PROCESSING
• The different levels of a sensory hierarchy
were connected in a SERIAL fashion.
• Information flows among the components
over just one pathway.
• Research: Multiple pathways called
PARALLEL SYSTEM
Until after 1960…..
• Sensory system are characterized by a
division of labor : Multiple specialized
areas, at multiple parallel pathways.
• Product of combined activity of different
interconnected cortical regions.
SOMETHING TO THINK
ABOUT
• What is top Down processing and Bottom
up processing?
• How does this influence the case of
depression?
INFOBIT
• iPods and other MP3 players can reach 120
decibels. At that level, you risk damage to
your hearing after only 7 1/2 minutes. How
do you know if the volume is too loud? It’s
too loud if someone three feet away can
hear your music, or if you need to remove
the ear piece to hear someone talking to you
The auditory system
• The Mechanism of Hearing
Sound
 ( MOLECULAR VIBRATIONS) A,F, C--( PERCEPTIONS) L, P, T,
Pure tones
Theories ( Fourier analysis and fundamental
frequency)
• Hearing begins with sound waves—
vibrations in air, water, or solid material.
The number of sound waves that pass
through a given point in one second is
called the sound’s frequency.
• When your sensory system experiences the
physical sensation of frequency, you also
have the psychological experience of pitch.
High-pitched sounds are high frequencies,
and
low-pitched
sounds
are
low
frequencies.
• Loudness of sound is a psychological
experience that corresponds to the height of
a sound wave, called amplitude. Amplitude
is measured in decibels (dB).
• The greater the amplitude, the higher the
decibels, and the louder the sound.
DIFFERENT WAVES OF
FREQUENCY
• You experience this combination—or
blending of frequencies—as timbre.
• Timbre is why you can recognize different
friends’ voices over the telephone.
SOMETHING TO THINK
ABOUT
• Why ear is a complex patterns of
vibrations, how this affects what
we hear/perceive?
• What happened if we combined
sine waves together?
• What happen if we combine 100,
200 qnd 300 Hz?
OUTER EAR
• The outer ear is the part you see. It is the
part of the ear that receives sound waves
and sends them down a passageway called
the auditory canal.
• At the end of the auditory canal is the
eardrum, which is a thin, flexible membrane
that vibrates in sequence with the sound
waves.
MIDDLE EAR AND OUTER
EAR
• The middle ear is an air-filled cavity that
begins on the other side of the eardrum.
• As the eardrum vibrates, it sets in motion
three tiny, interconnected bones
(Occicles)—the hammer, anvil, and
stirrup or malleus, incus and stapes
• When the eardrum vibrates from sound
waves, these bones also vibrate against the
cochlea, which is part of the inner ear.
• The cochlea (pronounced COKE-lee-ah) is
a coiled, fluid-filled tube that is lined with
special hair-like auditory receptor cells.
When these hair cells are stimulated by
sound wave vibration, they trigger the fi
ring of sensory neurons that form the
auditory nerve.
• Organ of corti ( basilar and tectorial
membrane)
• The auditory nerve then transmits sound
information to the brain.
Hearing Loss
• Two types of hearing loss, conduction and
sensorineural.
• Conduction hearing loss occurs when there
are physical problems sending sound waves
through the outer or middle ear.
Sensorineural hearing loss involves nerve
problems in the inner ear.
• Conduction hearing problems often involve
a punctured eardrum or damage to any of
the three bones in the middle ear.
• A common treatment for conduction
hearing loss is hearing aids, which are tiny
instruments worn just inside the outer ear.
Hearing aids change sound waves into
amplified vibrations and send them to the
inner ear.
• Sensorineural hearing loss is a more
common problem. It often occurs because
hair cells in the cochlea are damaged either
by disease, injury, or aging.
• The only means of restoring hearing in
people suffering from nerve deafness is a
cochlear implant, which is a miniature
electronic device that is surgically placed
into the cochlea.
• The implant changes sound waves into
electrical signals and sends them to the
auditory nerve, which transmits them to the
brain.
• Young children born with hearing loss are
the best candidates for this implant.
Why do some people hear voices
that aren’t really there?
• Inner speech vs actual speech
Ear to Auditory Cortex
• The axons of each
Auditory nerve
synapse in the
ipsilateral Cochlear
nuclei------which leads
to the superior olives
on both sides of the
brain stem at the same
level.
• The axons of the • The complexity of the
olivary
neurons
subcortical auditory
project via the lateral
pathways......make the
lemniscus
to
the
analysis of the sound
inferior colliculi---difficult------but there
where they synapse on
is one function of the
neurons that project to
subcortical auditory
the
medial
system -----the
geneculate nuclei of
localization of sounds
the thalamus.....which
in space.
is projected to the
primary
auditory
cortex.
Subcortical Mechanisms of
Sound Localization
• The
localization
of
sounds in space is
mediated by the lateral
and medial superior
olives but in different
ways.
• When
the
sound
originates to a person’s
left, it reaches the left ear
first-----louder left ear
Located in the temporal
lobe, hidden view
from lateral fissure.
TWO AREAS
Core region---surrounded by a band---called BELT---areas of secondary
cortex----outside the
belt is the
PARABELT AREAS
Streams of Auditory Cortex
• Anterior auditory
pathway---is more
involved in identifying
sounds (What)
• Posterior auditory
pathway-----is more
involved in locating
sounds (Where)
The Olfactory System
• The stimuli for smell are airborne
molecules.
Ex.
When you smell hot chocolate you
are sensing molecules that have left the hot
chocolate and traveled through the air
to your nose.
• These molecules then enter your nasal
passages and reach tiny receptor cells at the
top of the nasal cavity.
• These receptor cells then transmit neural
impulses containing smell information
through the olfactory nerve to the brain.
Once your brain has processed these neural
signals, you experience the hot chocolate’s
aroma
• The olfactory receptor cells are located in
the upper part of the nose-----embedded in a
layer of mucus-covered tissue---called
Olfactory Mucosa
• Cribriform plate ( porous portion of the
skull) where the axons passes through.
• Olfactory bulbs-where they synapse on
neurons that project via the olfactory tracts
to the brain.
Did you know that?
Humans have about 10 • Brain scans taken
while people are
million
olfactory
smelling objects find
receptors while dogs
that smells trigger
have 200 million
more brain activity in
receptors.
women than in men.
Research indicates that
women’s
smell
sensitivity is better
than that of men.
• Olfactory receptor proteins---located at the
membranes of the dendrites of the olfactory
receptor cells, where they can be stimulated
by circulating airborne chemicals in the
nasal passages
• Olfactory glomeruli----a cluster where the
olfactory receptor axons terminate. It
receives input from several thousand
olfactory receptor cells, all with the same
protein.
• Medial Temporal Lobes----includes the
Amygdala and Piriform cortex
• Piriform cortex- considered to be primary
olfactory cortex.
• Olfactory system- the only sensory system
whose major sensory pathway reaches the
cerebral cortex without first passing
through the thalamus
• The two major pathways ----projects
diffusely to the limbic system and to the
medial dorsal nuclei of the thalamus to the
orbitofrontal cortex-----the area of cortex on
the inferior surface of the frontal lobes next
to the orbits (eye sockets)
• Thalamic-orbitofrontal projection-mediate
the conscious perception of odors,
Eardrum- A thin, flexible membrane that
vibrates in sequence with sound waves
Cochlea- The coiled, fluid-filled tube in the
inner ear that contains hair-like auditory
receptors
Perception
“Perception refers to the interpretation of what we
take in through our senses. In terms of optical
illusions this means our eyes.”
Simply put, our brains are tricked into seeing
something which may or may not be real.
http://www.keele.ac.uk/depts/aa/widening/uniworld/webclub/rs/optical.htm
Factors that
Influence
Perception
 The Object of Perception:
some things in our environment tend to
attract attention
 Backgrounds and Surroundings
our surroundings at the moment of
perception will affect our perceptions
 The Perceiver
we each bring unique experiences and
personal points of view to each situation