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29 Cards in this Set
- Front
- Back
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Waveforms - type?
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combination of sinusoidal waves
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Phase?
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Temporal delay of the wave
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Characteristics of wave?
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- frequency (beats/cycles per time/sec)
- amplitude - phase (temporal delay of wave) |
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loudness? pitch? vowels/consonants
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loudness - amplitude (louder sound, more energy it carries, higher amplitude)
pitch - frequency phase - sort of related to vowels/consonants |
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fourier transform?
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mathematical theories - decompose wave form into some sort of sinusoidal waves.
Analyze wave/function according to individual sinusoidal components. Inverse fourier transform - take sum of sinusoid and revert it back to original space in mathematical terms |
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impedance/resistance mismatch?
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sound is compression of air molecules. if pressure goes through air then encounters wall, it will bounce back - mismatch.
brain needs to solve problem bc waves are in air, but neurons are in water. - transfer energy through series of cones in inner ear |
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pinna and concha - amplification of sound waves?
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physical structure used to increase concentration of the gradient
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why are ears convoluted?
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amplification of sound from different directions. ears evolved to specifically amplify sounds from human speach.
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1st impedance mismatch? and how resolved?
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when sound hits tympanic membrane, 1st impedance mismatch. 3 bones form lever connected to tympanic membrane - malleus, incus, and stapes. sound arrives at tympanic membrane, membrane moves, pushes bone lever back and forth which is connected to oval window.
levers amplify wave, compensating for impedance mismatch. |
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cochlea (basic)?
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coiled structure with base and apex
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basilar membrane
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membrane runs through cochlea, gets wider at the base. it is a mechanical resonator - oscillates depending on frequency of sound. every part of basilar membrane designed to oscillate at particular frequency
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resonanced is based on...
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size of object.
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where on basilar membrane does high frequency sound resonate?
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base
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low frequency sound resonates where on basilar membrane?
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apex
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fourier transfer in ears?
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basilar membrane - takes different frequencies and breaks them apart into their diff components. every sound (no matter how complicated) gets broken down into sinusoids and resonates different locations of basilar membrane based on frequencies
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how does this get relayed to brain?
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hair cells are on top of basilar membrane and touch organ of corti.
hair cells transduce mechanical energy into electrical potentials & have axons that connect to brain. hair cells have cilia that touch tectorial membrane. basilar membrane moves w/ respect to tectorial membrane & hair cells bend. bending of cilia opens channels that depolarize hair cells & trigger NT release & AP go to brain. |
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outer ears amplifies by...
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~ 100x
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elevation in sound?
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ears are asymmetric - amplify sounds differently that come from different elevations - helps us analyze sounds
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tonotopy
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different freq. of sounds, tones, pitches are mapped in different places of cochlea.
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inner ears - transduction
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by hair cells.
afferents - pathway into brain from inner hair cells efferent - goes from brain to periphery, outer hair cells |
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shear force?
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tectoral membrane + basilar membrane - diff insertion points so when move relative to each other, create shear force that opens channels in hair cells
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tip links of cilia? (cascade of events for depolarization)
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cilia differ in size - lines of increasing length linked together by "springs" (tip links)
connect to top of channel & open channel when cilia moves. K+ OUTSIDE of cell (only part of body w/ higher conc of K outside) bending pulls tip links which pulls channel & lets K+ ions into cell (typical neuron is Na+) - K+ is positive so hair cells get depolarized - K+ flows thru cell and depolarization opens Ca++ channels at base of hair cells, so Ca++ flows in synaptic vesicles then release NT, which diffuse to postsynaptic side (auditory nerve fiber) & nerve fiber has APs that get sent to brain. |
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amplitude coded by...
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amount of displacement of cilia
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"receptive field" of auditory neuron
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frequency it fires most. stimulus is sound.
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how brain measures phase?
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wave goes up, fires a lot, goes down, stops firing. hair cells tuned to phase of sound and likes to fire at particular time. w/ this, you can calculate phase of waves - by number of spikes, you know amplitude of wave, by shape, you can know phase
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auditory pathway as it leaves cochlea?
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afferent axons go thru 8th cranial nerve to cochlear nucleus - one on each side. right ear --> right nucleus (vice versa). neurons from cochlear nucleus send axons to superior olive (in pons). projections then become bilateral w/ ipsi & contralateral projections --> inferior colliculus (in midbrain) --> auditory thalamus (like LGN for visual system), --> primary auditory cortex (A1) --> secondary, tertiary, etc
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pons & medulla
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have to do with sound localization
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why does olive structure in pons receive ipsi and contra-lateral projections?
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neurons in olive that are sensitive to arrival time of APs coming from one ear or other ear.
(Animals use this to estimate location of sound) |
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how do you localize sound? (also, see lecture slide 29) use example - sound is coming from right side
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sound from right side hits right ear first, will go to olive on right. eventually, sound will hit left ear, but it will lag behind. APs going to olive are staggered and AP will reach olive on right side while left AP is still coming up. When AP hits neuron E, nothing will be on the left. when it hits neuron A, the left would have had enough time, so both APs reach olive at the same time. neuron will fire.
brain knows sound is on right side using delay + coincidence detector of both axons firing together |
