PSY 250 Lecture Notes - Lecture 36: Agraphia, American Sign Language, Lateral Sulcus
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Chapter 9: Hearing and Language Book Notes
A. Introduction Information
a. Heather Whitestone
i. First Miss America to have a handicap (Deafness)
ii. Became deaf at 18 months when being treated for meningitis
iii. He had a hearing aid
iv. Decided to get a cochlear implant when her son was hurt and noticed her
husband running to him and realized she could not hear her son crying
b. Receptor: a cell, often a specialized neuron that is suited by its structure and function to
respond to a particular form of energy, such as sound
c. Function is to convert that energy into a neural response
d. Adequate Stimulus: the energy form for which the receptor is specialize
e. Patterning of the stimulation (amplitude and timing of neural impulses) makes sensory
information meaningful
f. Sensation: the acquisition of sensory information
g. Perception: the interpretation of sensory information
B. Hearing
a. Cochlea: where the auditory stimulus is converted into neural impulses, contains a million
moving parts
b. Range of sensitivity to intensity is a million to one
c. Ability to hear low-intensity sounds is limited more by interference from the sound of
blood coursing through our veins and arteries than by the artery mechanism itself
d. We are able to hear frequencies ranging from 20 hertz to 20,000 Hz
e. We can detect a difference in frequencies of only 2 or 3 Hz
f. The Stimulus for Hearing
i. Adequate stimulus for audition is vibration in a conducting medium
ii. Conducting Mediums
1. Air
2. Water
3. Skull
iii. Frequency: the number of cycles or waves of alternating compression and
decompression of the vibrating medium that occur in a second
iv. Pitch: our experience of the frequency of a sound
v. Amplitude (intensity): the term for the physical energy in a sound
vi. Loudness: the term for our experience of sound energy
vii. Sounds can be classified as…
1. Pure Tones: only has one frequency
2. Complex Sounds: has several frequencies
g. The Auditory Mechanism
i. We must get information about the sound to the auditory complex to be able to
hear
ii. The Outer and Middle Ear
1. Pinna (outer ear): the flap the graces the side of your head
a. Captures the sound and then amplifies it slightly by funneling it
from the larger area of the pinna into the smaller area of the
auditory canal
b. Selects sounds in front of you, making it easier to focus on the
conversation you maybe having
2. Middle Ear
a. Tympanic Membrane (eardrum): a very thin membrane stretched
across the end of the auditory canal; its vibration transmits the
sound energy to the ossicles
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b. Tensor Tympani: a muscle that can stretch the ear drum lighter
or loosen it to adjust the sensitivity to changing sound levels
c. Ossicles: tiny bones that operate in lever fashion to transfer
vibration from the tympanic membrane to the cochlea
i. Malleus (hammer), incus (anvil), and stapes (stirrup)
ii. Provide additional amplification by concentrating the
energy collected from the larger tympanic membrane
onto the much smaller base of the stirrup, which rests on
the end of the cochlea
iii. Amplification is enough to compensate for the loss of
energy as the vibration passes from air to the denser
liquid inside the cochlea
iii. The Inner Ear
1. Cochlea: where the ear’s sound-analyzing structures are located
2. Subdivided by membranes into three fluid-filled chambers or canals
3. The stirrup rests on the Oval Window: a thin, flexible membrane on the
face of the vestibular canal
4. Vestibular Canal (scala vestibuli): the point of entry of sound energy into
the cochlea and connects to the tympanic canal
5. Tympanic Canal: at the far end of the cochlea through an opening called
the helicotrema
6. Helicotrema: allowed the pressure waves to travel through the cochlear
fluid into the tympanic canal more easily
7. Round Window: flexes outward with each sound wave and relieves the
pressure
8. Cochlear Canal: where the auditory receptors are located
9. Organ of Corti: the sound-analyzing structure that rest on the basilar
membrane
a. 4 rows of specialized cells called hair cells
b. Supporting cells
c. Tectorial membrane above the hair cells
d. Hair cells are receptors for auditory stimulation
e. Hair cells are very sensitive
f. Single row of 3,500 inner hair cells (receive 90-95% of the
auditory neurons and provide the majority of the information
about auditory stimulation)
g. Three rows of about 12,000 outer hair cells (increase the
cochlea’s sensitivity both by amplifying its output and by
sharpening the frequency tuning at the location of peak vibration
h. Damage to hair cells can cause hearing loss
iv. The Auditory Cortex
1. Neurons from the 2 cochleas make up part of the auditory nerves
2. Neurons pass through the brainstem nuclei to the inferior colliculi, to the
medial geniculate nucleus of the thalamus, and finally to the auditory
cortex in each temporal lobe
3. The left hemisphere is dominant for language in most people and the
right hemisphere is better at identifying different types of sounds
4. Auditory cortex is on the superior (upper) gyrus of the temporal lobe of
each hemisphere
5. Topographically Organized: neurons from adjacent receptor locations
project to adjacent cells in the cortex
6. Projections form a sort of map of the unrolled basilar membrane
7. Secondary auditory areas are involved in processing complex sounds
and understanding their meaning
8. Human primary auditory cortex has a secondary area surrounding it
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9. Auditory information also travels well beyond the auditory areas,
following the dorsal or ventral streams
10. Dorsal (where)
a. Flows from the auditory cortex through the parietal area, where
the brain combines information from other senses to locate the
sound in relation to the body and visual scene
b. Information then proceeds to the frontal lobes, where it can be
used for directing eye movements toward sound sources and for
planning movements
11. Ventral (what)
a. Active when the individual is identifying sounds
h. Frequency Analysis
i. Sounds vary in intensity and frequency and change rapidly
ii. It is the task of the cochlea and the auditory cortex to analyze these complex
patterns and convert the raw information into a meaningful experience
iii. Frequency Theories
1. Frequency Theory: assumes that the auditory mechanism transmits the
actual frequency of a sound to the auditory cortex for analysis there
2. Telephone Theory: believed that individual neurons in the auditory nerve
fired at the same frequency as the rate of vibration of the sound source
3. Volley Theory: states that groups of neurons follow the frequency of a
sound at higher frequencies, whereas a single neuron cannot
iv. Place Theory
1. Hermann von Helmholtz proposed that the basilar membrane was like a
series of piano strings, stretched progressively more loosely with
distance down the membrane
2. Invoked a principle from physics called resonance to explain how we
discriminate different frequencies
3. Resonance: the vibration of an object in sympathy with another vibrating
object
4. Resonance would cause the narrow base end of the membrane to
resonate more to high-frequency sounds, the middle portion to moderate
frequencies, and the wider apex (tip) to low frequencies
5. Place Theory: states that identifying the frequency of a sound depends
on the location of maximal vibration on the basilar membrane and which
neurons are firing most
6. Georg von Bekesy constructed mechanical models of the cochlea and
also observed the responses of the basilar membrane in cochleas he
removed from deceased subjects as diverse as elephants and human
7. Bekesy determined that its frequency selectivity is due to differences in
elasticity, with the membrane near the stirrup 100 times stiffer than at the
apical end
8. Tonotopic Map: each successive area responds to successively higher
frequencies
9. Place analysis is the reason we can hear with some clarity through bone
conduction
10. Frequency-Volley-Place Theory: individual neurons follow the frequency
of sounds up to about 500 Hz by firing at the same rate as the sound’s
frequency; then between 500 and 5,000 Hz, the frequency is tracked by
volleying, and place analysis takes over beyond that point
11. Frequency-Place Theory: frequency following by individual neurons
accounts for frequencies up to about 200 Hz and all remaining
frequencies are represented by the place of greatest activity
v. Analyzing Complex Sounds
1. Speech, music, and meaningful noises are made up of many frequencies
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Document Summary
First miss america to have a handicap (deafness) Became deaf at 18 months when being treated for meningitis. Adequate stimulus for audition is vibration in a conducting medium. Frequency: the number of cycles or waves of alternating compression and decompression of the vibrating medium that occur in a second. Pitch: our experience of the frequency of a sound. Amplitude (intensity): the term for the physical energy in a sound. Loudness: the term for our experience of sound energy. Sounds can be classified as : pure tones: only has one frequency, complex sounds: has several frequencies, the auditory mechanism, we must get information about the sound to the auditory complex to be able to hear. Provide additional amplification by concentrating the energy collected from the larger tympanic membrane onto the much smaller base of the stirrup, which rests on the end of the cochlea.
