Download The Brain, Processing, and the Ear

Presented by:
Maude Le Roux, OTR/L, RCTC
Sofia, Bulgaria
May 2012
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Neurons
that Fire
together,
wire
together!
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12 Cranial Nerves
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1. Olfactory Nerve
• Influences sense of smell
to enhance, dampen and
adapt to odors
• Directly projecting into
limbic system
(emotions)
• Arousal, bonding,
reproduction, memory
and safety
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2. Optic Nerve
• Peripheral and Central
Vision
• Monitoring, scanning,
searching environment
for possible danger
• Discrimination
• Direction of the eye,
hand, and body in and
through near and far
space
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3. Oculomotor; 4. Trochlear;
5. Abducens
 Extrinsic eye movements for
convergence, divergence,
scanning and tracking
 Involuntary eye movements
such as pupillary
constriction, dilation and
accommodation
 Binocular coordination to
support for depth perception,
acuity, fixation, and smooth
pursuits
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6. Trigeminal Nerve
 Muscles of mastication and
soft palate for sucking,
chewing, initiation of
swallowing, phonation
 Touch, pain, temperature
for eyes and temporal area
of face
 Serves Tensor Tympani,
scalp, face, teeth, sockets,
tongue, palate, mucosal
membrane of nose
(breath)
 Attention, articulation,
auditory processing
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7. Facial Nerve
 Facial Expression,
stapedius muscles
 Verbal / non-verbal
communication
 Salivation
 Tear glands
 Subcortical influences to
express emotions
 Taste
 Midline Orientation
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8. Vestibulocochlear Nerve
 Extensor Tone
throughout the body
 Balance
 Detection of position in
space
 Hearing
 Muscle tone, protective
reactions
 Equilibrium responses
 Orientation
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9. Glossopharyngeal Nerve
 Swallowing
 Pharynx, Larynx
 Gag reflex
 Phonation
 Taste - posterior third
 Oxygen consumption
 Blood pressure
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10. Vagus Nerve
 Muscles of palate, uvula
and palatal arch,
pharynx, vocal cords,
swallow, respiration,
disgestive function
 Heart rate, respiration.
Esophagus, stomach
 Taste – base of tongue
and palate
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Ear to the Eye: c.n. III and VI
Cranial Nerve III is Oculomotor and c.n.VI is Abducens, which controls
the movement of a single muscle, the lateral rectus muscle of the eye.
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Pathways of the Vestibular
Reflex. Cranial Nerves 3, 4, 6, 8,
and 11 are shown.
3=oculomotor
4=trochlear
6=abducens
8=vestibular/cochlear (hearing
and balance)
11=spinoaccessory, which
controls specific muscles of the
neck.
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11. Accessory Nerve
 Not true cranial nerve,
since receptors are
located in the spinal cord
 C1-5 input for respiration
 Joins Vagus nerve to
pharynx and larynx
 Trapezoid and
sternocleidomastoid
 Head posture / control
for gradation and
stability
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12. Hypoglossal Nerve
 Movement of the tongue
 Sucking, swallowing,
breathing
 Speech Language
 Self-regulation
 Mother – infant bonding
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Auditory
Pathway
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The Auditory Pathway
 First stop is the cochlear
nucleus in the brainstem.
 Nerve fibres originating from
different parts of the cochlea
are geometrically mapped
onto specific regions within
the cochlear nucleus.
 Spatial mapping of the
cochlea onto the cochlear
nucleus translates, therefore,
into a map of preferred
stimulus frequency within
the cochlear nucleus
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Auditory Pathway (Continued)
 Tonotopic map very similar
to the retinotopic map
found in the visual system.
 This spatial organization
allows the nervous system
to analyze the overall
frequency content of an
auditory stimulus.
 Some cochlear nucleus
neurons fire only a single
action potential abruptly
and reliably just at the
onset of a tone at their
preferred frequency
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Auditory Pathway (continued)
 Neurons extract precise
information about the
time of onset of an
arriving sound stimulus
 Other neurons remain
silent at the onset of a
stimulus, then increase
their firing rate during a
sustained tone
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Auditory Pathway (continued)
 Two parallel pathways lead
from the cochlear nucleus
to the inferior nucleus.
 A direct, bilateral
projection of axons of the
cochlear nucleus neurons.
 Indirect path via an
intermediate brainstem
nucleus, the superior
olivary nucleus (superior
olive)
 Give rise to efferent axons
that project back to the
cochlea
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Auditory Pathway (continued)
 Main function of superior
olive is to process aspects of
auditory information related
to the localization of sound
sources in the external
environment.
 Sounds coming from left or
right side of head are
differentiated through higher
intensity and difference
(microseconds) in time it
reaches both ears.
 The Superior Olive registers
these very refined differences.
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Superior
Olive
Auditory Pathway (continued)
 When we turn our heads
from side to side to localize a
sound, you are trying to help
your superior olives to gain
more information to track
down the source.
 Superior Olive and the
cochlear nucleus neurons join
to form the track of the
lateral lemniscis.
 This track ends in the inferior
colliculus
 Inferior colliculus on each
side of the brain receives
information from both ears.
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Auditory Pathway (continued)
 The thalamus is the gateway
to the auditory cortex
 The medial geniculate
nucleus is the nucleus
relevant to the auditory
system
 Projections from here to the
cortex is primarily ipsilateral
 The primary auditory cortex
is located in superior part of
the temporal lobe of the
cerebral cortex (Brodmann’s
areas 41 and 42).
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Auditory Pathway (continued)
 Tonotopic map of cochlear




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nucleus in brainstem also
present in auditory cortex.
This map is represented
multiple times for different
functions of auditory system.
One dimension is frequency
columns
Cells have same frequency
preference for sound stimuli
Columns of frequency
preference range consistently
from low to high frequency
across the surface of the
cortex
Auditory Pathway (continued)
 Again, you find a similar




orientation as in the visual
cortex.
Other axis of two dimensional
array in the auditory cortex
consists of binaural columns
Summation column – cells
respond best to sound stimuli
presented simultaneously to
both ears
Suppression column – cells
respond best to a stimulus in
only one ear.
Functional significance not quite
extrapolated by science as yet.
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Thank you
for listening!
Have a nice day!
The end