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PSYC 440 > sensation and perception - sound > Flashcards

sensation and perception - sound Flashcards

1
Q

What is tonotopy?

A

the fact that the way things get activated in the cochlea is not related to space but to the frequencies that make up a sound

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2
Q

How does sound travel?

A

as waves of pressure through the air and the sound of a voice has a source and that is propagating out from your mouth and hitting your ears

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3
Q

What is the basic currency for sound communication and sound signaling?

A

time

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4
Q

How is sound conveyed?

A

as transverse waves of air pressure

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5
Q

When we visualize sound using a spectrogram what do we see?

A

a wave form going up and down
-if a sound is 440Hz that means we will see it go up and down 44 time per second which means there is an increase and decrease in frequency of the sound 44 times

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6
Q

How do you go up an octave?

A

double the frequencies

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7
Q

How do you get a pure tone?

A

if you extract the frequencies

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8
Q

In the auditory system what type of frequcny are we interested in?

A

temporal frequency of sound waves

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9
Q

What math is used to describe frequcny in both visual and auditory domains?

A

the fourier transform

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10
Q

How come you are usually not hearing alot of pure tones?

A

most of the sounds you hear the sound is resonating in a cavity which is giving it some sort of camber and that is not because the base frequcny is different it is because that frequncy has na overtone that gets dampened as a result of the cavity form which teh soudn is coming from

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11
Q

Where do pure tones come from?

A

they do not occur in nature need to use a tuning fork to get one

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12
Q

What is encoded in the auditory system?

A

temporal frequcny or how frequntly the sound is getting louder and quieter is getting encoded

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13
Q

What is the Gabor filter?

A

a convolution of a sine or cosine wave at a particular spatial frequcny with a gaussian wave over it to yield a joint representation of spatial frequncy and location

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14
Q

In the auditory system can you compress speech?

A

there are limits to what you can compress and you can compress speech and get info out of it but there is a limit on it

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15
Q

What is an important difference between auditory and visual input?

A

all spatial frequncies in a visual array are available instantaneously and in parallel
-temporal frequencies of sound unfold over time
-so can show the word freuqncy and you will see it all in 50 ms
-but cannot compress speech into 50ms that you can hear it

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16
Q

What is frequecny transduced by?

A

the cochlea

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17
Q

How does sound get into the brain?

A

bones in the middle ear vibrate and the tympanic membrane displaces fluid which opens and closes hair cells in the basialr membrane and this is a place code for frequncy with close to the oval window being high and near the cochlear apex is low frequcnies - different frequencies will land at different spots of the cohlea and the cohlea does the fourier transofrm and decomposes the stimulus into a place code

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18
Q

What does the basilar membrane do?

A

transduces vibrations from the middle ear

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19
Q

What do locations on the basilar membrane have?

A

they have a best frequency

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20
Q

What is a place code?

A

the result of the fourier transform conducted by the cochlea and is a tonotopic representation

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21
Q

How does tonotopy compare with retinotopy?

A

tonotopic is tone represnted by position while retinotopy is where a posiiton on the retina is related to a position in the visual field

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22
Q

What does tonotopic mean?

A

tone represented by position

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23
Q

As you get a higher frequency what happens to the tuning curves?

A

they get more precise

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24
Q

How is the place code biological?

A

there is a distribution of frequency so these locations have tuning functions so the best frequency for a hair cells or its neurons is in the cochlear membrane

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25
Q

How is tonotopy preserved?

A

throughout the auditory system - including subcortical areas

26
Q

From where does the auditory nerve project to?

A

from the cochlea to the cochlear nucleus

27
Q

How come by the time the information gets to the primary auditory cortex it is fairly processed?

A

there is a lack of strict hierarchical organization - a region gets a ton of parallel inputs from the subcortical auditroy system and all of these parts have a bunch of feed forward and feedback mechanisms so by the time it gets to the auditroy cortex it is fairly processed
-there are also direct projections from the thalamus to the other cortcial auditory areas

28
Q

How are what and where somewhat recoverable from the retina?

A

what = activity of rods and cones
where = where on the retina - it is a bit more complicated for where in space like you need eyes and head for depth perception

29
Q

How are what and where determined in the auditory system?

A

what - the frequency information i.e. location on the cochlea and tonotopic maps that preserve this organization up through the cortex
where - interaural time difference and interaural intensity difference

30
Q

What neurons measure interaural intensity difference?

A

LSO - uses subtraction that compares the signal coming in from both ears

31
Q

What neurons measure interaural time difference?

A

MSO - (MNTB also) - has the delay line where the relative timing and coincidence detections properties of neurons or treating them as an end gate to de time to determine the info

32
Q

At what speed do sound waves move through space?

A

slowly through space at about 10^-6 the speed of light

33
Q

What does the speed of sound waves mean if a sound is directly to your left?

A

the sound it emits will reach your left ear ever so slightly faster than teh right ear and the difference is measureable

34
Q

Can you detect if sound is in front of or behind you if it is perfectly 90 degrees?

A

no - cannot use interaural time difference

35
Q

What appear to be in the MSO and what do they do?

A

delay lines; axons of variable lenghts which send inputs to neurons in the MSO from the two ears

36
Q

How do delay lines in the MSO work?

A

they work as coincidence detectors such that they are only activated when they receive input from the two ears at the same time

37
Q

What is the neuron in the middle of delay lines tuned to?

A

simultaneous activity on the left and right

38
Q

What does interaural intensity difference depend on?

A

the sound source and frequency of the sound

39
Q

How are high frequency versus low frequency sounds interpreted via interaural intensity difference?

A

-high frequency sounds are absorbed by yoir head whcih causes the contralateral ear to have a low frequency acoustic shawdow causing dampening of it allowing you to use iid to figure out where the sound is coming from
-low frequency sounds are not absorbed by the head so cannot use iid but can use itd

40
Q

What happens when the same signal hits the two ears with the same amplitude?

A

they cancel each other out and activity stays at baseline

41
Q

What happens when the ipsi>contra?

A

the excitation from CNipsi goes up
the inhibition from the CNcontra does down

42
Q

What is a simple description of how the lateral superior olive works to amplify interaural intensity differences?

A

-excitatory inputs from the ipsilateral ear
-inhibitory inputs from the contralateral ear

-Have to build a circuit that uses differences in intensity between two ears to determine information and excitatory input from Ipsilateal ear and inhibitory input from contralaletrla ear then the intensity difference amplifier will produce a high number so if it a psiiitve value the thing is closer on the right than left and negative means closer to left and then opposite for otehr side and smaller difference might be at an angle and larger difference if completely far apart

43
Q

In an fmri study using block design for what and where for auditory system what is the design?

A

-one block is localization
-one block is recognition
-one block is rest

-both the actuve and passive listening trials begin a bit more than 6s after the last data acquistion
-the data acquisition starts about 3.5s after the beginning of the critical stimulus

44
Q

Why does the the data acquisition starts about 3.5s after the beginning of the critical stimulus? THERE ARE TWO MAIN THINGS

A

-the scanner itslef is very loud when data are being collected
-the noise is generated by mechanical consequences of the large changes in magnetic field that are part of data collection
-you cannot collect mri data without making noise
-the audiotry system is good at adapting to repetitive stimuli so for many experiments it is not necessary to go to such extremes to avoid noise related brain atcivity

-the other thing is that the BOLD response peaks typically at around 5s and by around 10s the response tends to overshoot the baseline meaning it is slightly depressed - so this fmri protocol was desigend to catch the peak of the respnse to the target stimuli and the trough of the auditory response to the scanner

45
Q

What are the stimuli they use for recognition in the study?

A

5s background sounds indicating different auditory scenes (train station, marketplace)
2s unusual sound like hammering or animal vocalizations

46
Q

What are the stimuli they use for localization in the study?

A

5s background noise roving in ITD
two 500ms targets 1.5s apart presented with ITDs simulating either the same or different hemifield locations

47
Q

What are the active and passive tasks for the study?

A

active - listen for animal sounds or same differnet judgemnt for location
passive - just listen to stimuli wihtout instructions

48
Q

What were the results of the study in the active task?

A

-behaviorally the recongiiotn task was easier than the location task
-relatuve to rest both tasks actuavte a number of subcortical and cortical audiotry areas very strongly
-this validates the sparse scannig approach
-it is not trivial to light up auditory thalamus in an mri study due to auditory noise issues
-cannot recongize the location versus recognition differenence because the supeiror olive is like two voxels so cant divide into MSO and LSO

49
Q

What were the results of the study in the recogniiton versus localization contrast?

A

-red is the areas where localization caused more activity than recognition
-green is the areas where recognition caused more activity than localization
-what includes - middle and ventral temporal areas, lateral occipital cortex, inferior frontal gyrus
-where includes the superior parietal lobe and the premotor cortex

50
Q

What does the posterior parietal lobe tend to be involved in?

A

spatial processing

51
Q

What does the anterior portion of the temporal lobe tend to be involved in?

A

comprehenesion

52
Q

What were the results of the passive task in teh study?

A

there is must less extensive effect of location vs recongiton stimuli wihtout task demands

-but still - anterior temporal actiity and right ventral interior frontal gurys for what
-parietal atcivity for where

53
Q

In the parietal lobe where pathway what can the PPc receive input from?

A

V1 and A1

54
Q

In the parietal lobe where pathway where does the PPC output to?

A

DLPFC (dorsolateralPFC)
(A1 can also send projections to here)

55
Q

In the temporal lobe what pathway what does it receive input from?

A

VI in the IT (inferior)
A1 in the ST (superior)
also middle

56
Q

In the temporal lobe what pathway what does it output to?

A

VLPFC
-A1 can also send here

57
Q

Why did we discuss this paper/study in particular?

A

-there are some problems - recongition task was easier than loclaization causing some addiitonal medial activation; large unexplained differences between active and passive tasks

-paper allowed us to review fmri meaurements and dorsal and ventral streams of brain

58
Q

What does a meta analysis show?

A

take a group of related studies and summarizing data and takes the results of a bunch of inferential tests and asks across studies how likely are the results due to chance - can compare effect sizes for simpler data sets - each of these points reflects a difference between a spatial task and other task - more blue (spatial) on dorsal and more red (non-spatial) on ventral - means dorsal is where and ventral is what

59
Q

Since we just get frequency from the cohlea what is inferred by the audiotry system?

A

loudness, pitch, and location

60
Q

Where is location computed?

A

subcortically - using differences between the timing ITD and intensity IID of sound waves as they hit two ears

61
Q

What is there growing evidence for in the cortical pathways in the auditory system that represent location and identity?

A

that they mirror the dorsal and ventral streams in visual processing - run in parallel functionally and anatomically to what we see in the visual system

62
Q
A

PSYC 440 (15 decks)

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