Transcript Sensation - Schoolwires

Audition
Frequency and Amplitude

Audition
 the sense of hearing
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Frequency
 the number of complete wavelengths that
pass a point in a given time = pitch
 Pitch (wave frequency, Hz)
 High frequency = high pitch
 low frequency = low pitch
Amplitude

Amplitude: height of sound wave = loudness of
sound
 Timbre: quality, complexity of sound

Average human: hears tones from 20Hz to
20,000Hz.
 Women tend to hear higher frequencies
 Theory: men = Louder activities more often…
The Intensity of Some
Common Sounds
From Waves to Sound
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Outer Ear
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Middle Ear
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Channels sound wave through auditory canal to
eardrum
Eardrum: Membrane/ converts wave to vibrations
Vibrations pass through piston (hammer, anvil,
stirrup: smallest bones in human body!) piston
concentrates vibrations of the eardrum on the
cochlea’s oval window
Inner Ear
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Cochlea: converts vibrations into neural activity
(vibration = ripples in basilar membrane fluid
Bending hair cells = auditory neural impulse
In other words…
 From
sound waves to vibrations to fluid
waves to neural impulse to auditory cortex
(temporal lobe) = hearing!
Hair Cells: Basilar Membrane
How do we discern pitch?
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Place Theory
 Specific places along the basilar membrane
match a tone with a particular pitch
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Frequency Theory

rate of sound wave = rate of neural
impulses to the brain (# of neural impulses
determines pitch) ex. 100 sound
waves/second = 100 neural impulses =
pitch)
How We Locate Sounds
 Brain
analyzes differences in what is
heard by each ear to determine where
sound is coming from… (3 dimensional)
Hearing Loss
1.
2.
3.
4.
5.
Most common physical disability
35 million Americans (500 million worldwide)
Recent study: 60% of American college
students suffer from high frequency hearing
loss.
Each 5 db increase, time it takes for
permanent damage cut in half (after 85)
Men: greater degree of hearing loss at every
age (loud music or changes in cochlea that
restrict blood supply to neural elements?)
Audition
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Conduction Hearing Loss
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caused by damage to the mechanical
system that conducts sound waves to the
cochlea (Ear drum, hammer, anvil, stirrup)
Nerve Hearing Loss

hearing loss caused by damage to the
cochlea’s receptor cells or to the auditory
nerve (hairs in basilar membrane not
regenerative)
Tinnitus
 Damage
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to auditory ear (ringing in ears)
Advanced case is incapacitating
Shell shock (combat zones)
tinnitus masker: “ocean waves or radio static”
Helen Keller
 What
would be more difficult, being blind
or deaf?
 “…deafness
to be a much greater
handicap than blindness… Blindness cuts
people off from things. Deafness cuts
people off from people.”
Cochlear Implants
 Nerve
deafness
 “bionic ear”
 Stimulates sites on auditory nerve
Audition

Amplitude required for
perception relative to
20-29 year-old group
Older people tend to hear low
frequencies well but suffer hearing loss
for high frequencies
1
time
10
times
100
times
1000
times
32
64
128
256
512
1024 2048 4096
8192 16384
Frequency of tone in waves per second
Low
Pitch
High
True or False?
1. Hard of hearing people need all sounds
amplified.
2. Blind musicians are more likely than
sighted ones to develop perfect pitch.
3. Deaf people’s auditory cortex becomes
responsive to touch and visual input.
 Sensory
Compensation / plasticity
Touch
 Skin
senses: pressure, warmth, cold, pain
 Which is the only sensation identifiable
with skin receptors?

Pressure
 The
Rubber hand illusion (demo)
Touch
Pain
 Pain
= sensation + brain + expectation
 “No brain, no pain”
 More complex / no one stimulus / neural
cord, no special receptors
 Research shows extent of pain is more
influential than duration (medical
procedures)
Pain
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Gate-Control Theory
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Theory: spinal cord contains a
neurological “gate” that blocks pain
signals or allows them to pass on to the
brain
Small nerve fibers: conduct pain signals
Small nerve fibers open / activate neural
gate
Large nerve fibers close gate (shut off
pain)
Chronic Pain
 Pain=
physiological and psychological
 Treat by stimulating large neural fibers (to
close the gate…)

1
Acupuncture, massage, electrical stimulation)
in 6 Americans:100 billion total expenses
Reactions to pain..
 Why
do we rub something when we hurt
it?

Create competing stimulation that will block
some of the pain impulses… (“Makes it feel
better…”)
Taste

Taste Sensations
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sweet
sour
salty
Bitter
Umami (meaty taste) monosodium glutamate
Sensory Interaction

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the principle that one sense may influence
another (all senses)
Ex: the smell of food influences its taste
Taste: A Chemical Sense
 Each
bump on your tongue = 200 taste
buds
 Taste sensitivity decreases with age
 Sensory interaction: taste + texture +smell
= flavor
 T-F
You can taste without your tongue.
(Taste receptors in back and roof of mouth.)
New Studies
 Tongue
and taste: Place theory outdated
 Taste is comprehensive over tongue
Senses Influence Each Other…
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Sensory Interaction
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the principle that one sense may influence
another (all senses)
Ex: the smell of food influences its taste
Synaesthesia (“to perceive together”)
 joining of senses / one sense stimulates
another
 Feels shapes when taste / smell food
 See colors in response to pain
 Most common: see numbers / letters in colors
 Recent study: 1 in 2,000 - 1 male to 6 female
 Theory: cross-activation of adjacent brain
regions
Smell

Olfaction
 A chemical sense
 Process
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Molecules of substance / air / 5 million receptor
cells @ top of each nasal cavity
Impulse sent to brain through axon fibers
Odors recognized individually
Odor molecules / neural receptors (key and lock)
10,000 odors detected! Peak at early adulthood
Olfactory bulb > amygdala > hippocampus >
cortex (why smell evokes emotions, memories)
Smell
Olfactory
nerve
Olfactory
bulb
Nasal
passage
Receptor cells in
olfactory membrane
Gender and Senses

Detecting men from women: smell
 Research confirms: “hands, breath and shirts” can distinguish the genders (pheromones)
 Women better “sniffers” than men
Age, Sex and Sense of
Smell
Number
of correct
answers
Women and young adults
have best sense of smell
4
Women
3
Men
2
0
10-19
20-29
30-39
40-49
50-59
60-69
Age Group
70-79
80-89 90-99
Body Position and Movement
(Sensorimotor Coordination)
 Kinesthesis
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the system for sensing the position and
movement of individual body parts
Vestibular Sense
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Monitors head (and thus bodies) movement
Sense of balance (equalibrium)
Inner ear: semicircular canals, vestibular
sacs = fluid = hair-like receptors = impulse
to cerebellum (Vertigo)
Make sense now…?