PSY 250 Lecture Notes - Lecture 48: Optic Chiasm, Language Disorder, Parsley
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Study Guide Exam 3 Chapters 9 -11
- Chapter 9: Hearing and Language
- Know the Following Definitions
- 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; function is to convert that energy
into a neural response
- Adequate Stimulus: the energy form for which the receptor is specialized
- Sensation: the acquisition of sensory information
- Perception: the interpretation of sensory information
- The Stimulus for Hearing
- Frequency: the numbers 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
- The Outer and Middle Ear
- Tympanic Membrane: first part of the middle ear; eardrum; a very thin membrane
stretched across the end of the auditory canal; its vibration transmits the sound energy to
the ossicles
- Ossicles: tiny bones that operate in lever fashion to transfer vibration from the tympanic
membrane to the cochlea
- Hammer (malleus), anvil (incus), and stirrup (stapes)
- 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
- Amplification is enough to compensate for the loss of energy as the vibration
passes from air to the denser liquid inside the cochlea
- Not passive players in the auditory process
- The muscles attached to them tighten the joints to increase sensitivity to
soft sounds and loosen the connections to dampen loud sounds
- The Inner Ear
- Cochlear Canal: where the auditory receptors are located
- Organ of Corti: the sound-analyzing structure that rests on the basilar membrane
- Consists of 4 rows of specialized cells called hair cells and the tectorial
membrane above the hair cells
- Basilar Membrane: the membrane in the cochlea that separates the cochlear canal from
the tympanic canal, and on which the organ of Corti is located
- Tectorial Membrane: a shelf like membrane overlying the hair cells and the basilar
membrane in the cochlea
- Outer and Inner Hair Cells
- Outer Hair Cells: three rows of about 12,000 cells located on the basilar
membrane toward the outside of the cochlea’s coil; they amplify the cochlea’s
output and sharpen frequency, tuning, possibly by adjusting the tension of the
tectorial membrane
- Inner Hair Cells: a single row of about 3,500 hair cells located on the basilar
membrane toward the inside of the cochlea’s coil; they produce most, if not all,
of the auditory signal
- The Auditory Cortex
- Neurons from the 2 cochleas make up part of the auditory nerves
- 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
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- The left hemisphere is dominant for language in most people and the right hemisphere is
better at identifying different types of sounds
- Auditory cortex is on the superior (upper) gyrus of the temporal lobe of each hemisphere
- Topographically Organized: neurons from adjacent receptor locations project to adjacent
cells in the cortex
- Projections form a sort of map of the unrolled basilar membrane
- Secondary auditory areas are involved in processing complex sounds and understanding
their meaning
- Human primary auditory cortex has a secondary area surrounding it
- Auditory information also travels well beyond the auditory areas, following the dorsal or
ventral streams
- Dorsal (where): 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
- Information then proceeds to the frontal lobes, where it can be used for directing
eye movements toward sound sources and for planning movements
- Ventral (what): active when the individual is identifying sounds
- Frequency Theories
- Frequency Theory: assumes that the auditory mechanism transmits the actual frequency
of a sound to the auditory cortex for analysis there
- Telephone Theory: believed that individual neurons in the auditory nerve fired at the
same frequency as the rate of vibration of the sound source
- Volley Theory: states that groups of neurons follow the frequency of a sound at higher
frequencies, whereas a single neuron cannot
- Place Theory
- Hermann von Helmholtz proposed that the basilar membrane was like a series of
piano strings, stretched progressively more loosely with distance down the
membrane
- Invoked a principle from physics called resonance to explain how we
discriminate different frequencies
- Resonance: the vibration of an object in sympathy with another vibrating object
- 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
- 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
- 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
- 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
- Tonotopic Map: each successive area responds to successively higher
frequencies
- Place analysis is the reason we can hear with some clarity through bone
conduction
- 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
- 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
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3
- Cocktail Party Effect: the ability to sort out meaningful auditory messages from a complex
background of sounds
- Language and Aphasia
- Language: it is not limited to speech but includes the generation and understanding of
written, spoken, and gestural communication
- Communication through language has important survival value and is inestimably
important to human social relationships
- Aphasia: language impairment caused by damage to the brain
- Broca’s Area is located in the frontal area anterior to the motor cortex
- Wernicke’s Area is located in the posterior portion of the left temporal lobe
- Broca’s Area
- Broca’s Aphasia: impairment caused by damage to Broca’s Area and
surrounding cortical and subcortical areas
- Example
- Doctor: Why are you in the hospital, Mr. Ford?
- Mr. Ford: Arm no good. Speech… can’t say… talk, you see.
- Doctor: What happened to make you lose your speech?
- Mr. Ford: Head, fall, Jesus Christ, me no good, str, str… oh Jesus…
stroke.
- Doctor: I see. Could you tell me, Mr. Ford, what you’ve been doing in
the hospital?
- Mr. Ford: Yes, sure. Me go, er, uh, P.T. none o’cot, speech… two
times… read… wr… ripe, er rike, er, write… practice… getting better.
- Symptoms
- Speech is not fluent
- Have trouble finding the right words (anomia)
- Have difficulty with articulation
- Speech lack grammatical words (agrammatic
- Wernicke’s Area
- Wernicke’s Aphasia: person has difficulty understanding and producing spoken
and written language
- Also known as receptive aphasia
- Speech is fluent but meaningless (word salad)
- Example
- A patient asked to describe a picture of two boys stealing cookies
behind a woman’s back said…
- “Mother is away here worker her work to get her better, but when she’s
looking the two boys looking in the other part. She’s working another
time.”
- Dyslexia: an impairment of reading
- Can be acquired, through damage, but its origin is more often developmental
- Developmental dyslexia is partially genetic, with an estimated heritability between 40-
60%
- Four genes are involved in neuron guidance and migration, and two contribute to cell
functioning
- Visual-perceptual symptoms of dyslexia (reading words backwards, confuses mirror-
image letters, and has trouble fixating on printed words [move around the page])
- Prosody: the use of intonation, emphasis, and rhythm to convey meaning in speech
- Right hemisphere role in language
___________________________________________________________________________________________
- Chapter 10: Vision and Visual Perception
- The Visible Spectrum
- To understand we need to start describing the adequate stimulus
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Document Summary
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; function is to convert that energy into a neural response. Adequate stimulus: the energy form for which the receptor is specialized. Frequency: the numbers 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. Tympanic membrane: first part of the middle ear; eardrum; a very thin membrane stretched across the end of the auditory canal; its vibration transmits the sound energy to the ossicles. Ossicles: tiny bones that operate in lever fashion to transfer vibration from the tympanic membrane to the cochlea. Hammer (malleus), anvil (incus), and stirrup (stapes)
