~Chapter 12 - Lecture Section 12.1 Flashcards
What is Auditory Space?
We are able to perceive objects and events located at specific positions in space based on sound alone.
Auditory Space is talking about the stimulus, the info about object location that is available
What is Auditory Localization?
We can localize an object’s position in space based on sound.
Auditory Localization is the perceptual ability for us to take advantage of the info of Auditory Space.
Auditory Localization is often described in coordinates in ___ dimensions
3
What are the 3 coordinates used to describe Auditory Localization?
Azimuth, Elevation, and Distance
Azimuth is the ___ meridian, such as ___ and ___.
horizontal // left // right
Elevation is the ___ meridian, such as ___ and ___.
vertical // up // down
There are not auditory mechanisms to determine ___.
distance
Azimuth and Elevation are usually reported in ___ to account for ___.
degrees // absolute Distance
Are people generally good or bad at localizing sounds?
People are pretty good at localizing sounds
When subjects were blindfolded and asked to identify sounds coming from inside the dome, researchers found that people are most accurate for detecting the location of sounds ___, with an error of ___ degrees.
directly in front of them // 2-3.5
When subjects were blindfolded and asked to identify sounds coming from inside the dome, researchers found that people are least accurate for detecting the location of sounds ___, with an error of ___ degrees.
around the side, above, and behind the head // 20
The Primary receptor for sound (the Cochlea) detects ___ and ___ of sounds, not ___.
frequencies // intensity // space
The Auditory system uses ___, similar to the visual system using ___.
Location Cues // Depth cues
What are Binaural Cues?
Cues that require two ears
What are Monaural Cues?
Cues that require only one ear
Monaural Cues include the ___ and ___.
Head // Pinnae
Binaural Cues use ___ and ___.
Interaural Time Difference (ITD) // Interaural Level Difference (ILD)
What is the speed of sound?
340m/s
What does ITD rely on?
ITD relies on the fact that the Speed of sound 340m/s is pretty slow in terms of how fast the nervous system operates.
When sound is coming from the front, sound waves arrive to the Left and Right ears at ___ time(s), and the ITD = ___.
the same // 0
When sound is played from the side, sound travels ___ enough that there is ___ from when sound arrives at the near ear to when it activates the far ear, the ITD = ___.
slow // a detectable difference // > 0 (greater than 0)
ITD is really intuitive if you consider ___.
Aperiodic sounds
What does it mean when the Tympanic Membranes are moving out of phase?
One is being pushed in and the other is being pushed out
The Tympanic Membrane is pushed in when it’s struck by ___.
Condensation
The Tympanic Membrane is pulled out when it overlays a ___.
Refraction
When sounds are being played from the side and the wavelengths are correct, there will be times when the Tympanic Membranes are moving ___.
Out of phase
What does it mean when the Tympanic Membranes are moving in phase?
If a continuous Periodic Sound Pure Tone is being played from the front, both eardrums would be pushed in or pulled out at the same time.
For continuous sounds, Interaural Time Difference could better be described as ___.
Interaural Phase Difference
The ITD can only detect Phase Differences for relatively ___ wavelengths (___Hz), because the wavelength has to be ___ enough such that when one eardrum is pushed in, the other is pulled out. If the wavelength is too ___, there can be a lot of ___ info because there could be many wavelengths between the ears.
long // low frequencies ~20 – 1000 // long // short // lost
When sound played from the side, our head creates a barrier that ___ the intensity of sounds that reach the ___ ear, the head casts an ___.
reduces // far // Acoustic Shadow
For high-frequency information, the sound will be ___ for the ___ ear in an unobstructed path.
louder // near
For the far ear, it will be ___ because some of that sound energy is being ___ by the head.
quieter // absorbed
Sound waves will bounce off of ___ objects, but they will pass around ___ objects.
large // small
The ILD cue is only available when the wavelength of the sound is ___ than the width of the head, around ___Hz.
smaller // 1000 – 20,000
For short wavelengths, due to a ___ coming from the side, there is a nice Acoustic Shadow being cast, this will lead to a ___ ILD.
high frequency // strong
For ___ with a long wavelength coming from the side, there is no ___ cast and there will be the same ___ reaching the Near ear vs the Far ear.
lower frequencies // Acoustic Shadow // intensity
If sound is coming directly from the front, it will strike both ears with ___ intensity because no ___ is protecting any of the ears.
equal // Acoustic Shadow
Which cues are used to judge Azimuth?
Both Interaural Time Difference and Interaural Level Difference are used to judge Azimuth
Interaural Time Difference and Interaural Level Difference have ___.
complimentary Frequency Requirements
The Interaural Time Difference affects Azimuth judgments only for ___ stimuli, around ___Hz. This is because sound frequencies that are too high can create errors if there are many wavelengths between the near ear and the far ear.
low-frequency // 20-1000
Interaural Level Difference affects Azimuth judgments only for ___ stimuli around ___Hz.
high-frequency // 1,000-20,000
True or False: Interaural Time Difference and Interaural Level Difference complement each other to cover the entire range of sound frequencies.
True
Binaural Cues don’t help much in judging ___.
sound elevation
If we have 3 sound locations directly at the Midline, going upward, all of the sound info from these sources would have an ITD and ILD of ___, so those two pieces of info have nothing to contribute to the perception of ___.
0 // elevation
Usually, before a sound stimulus can enter the auditory canal, it first bounces off and interacts with the ___ and ___.
Head // Pinnae
There is a difference between the sound characteristics at the ___ VS the sound characteristics entering the ___.
source // auditory canal
Due to the shape of the Pinnae, there are more ___ patterns of constructive and destructive ___ with incoming or reflected sound waves, and different frequencies will be affected in different ways depending on the ___ of the sound coming in.
complex // interference // elevation
It is called a “Spectral Cue” because certain ___ are increased or decreased depending on the source’s ___.
frequencies // position
If a sound is played at 40 degrees elevation, Lower frequencies undergo ___ interference, so their power is ___ a bit. Mid frequencies undergo ___ interference, and their power is ___ a little bit. High frequencies undergo ___ interference such that they are a little bit ___.
constructive // increased // destructive // decreased // constructive // stronger
If the sound is played at 0 degrees elevation, there is not as much ___ interference. There is a different shape of ___ interference through the midrange. There is a different shape of ___ interference in the high frequencies.
constructive // destructive // constructive
When the sound is played at 40 degrees below the ear, there is a different shape of ___ interference through the midrange. There is a different shape of ___ interference in the high frequencies
destructive // constructive
It is a pattern of constructive and destructive interference that gives a ___ for sound elevation.
unique signature
Why are Spectral Cues a Monaural Cue?
Because this information is produced by the constructive and destructive interference pattern that is created by the Pinna, you only need 1 pinnae/one ear for this, hence it is a Monaural Cue.
Spectral Cues can be used to localize sounds at different ___.
elevations
In the Pre-treatment condition, Subjects were asked to judge the Azimuth and Elevation of sounds under normal circumstance, what did researchers find?
Subjects have fairly accurate representation of azimuth and elevation
-There is fairly accurate correspondence between the perceptual judgement and the physical stimulus.
On Day 0, subjects Pinnae are reshaped with a plug, which changes the shape of the Pinnae, and therefore changes the head and pinnae-related spectral cues that are available, what did researchers find?
Subjects can still accurately judge the Azimuth, but the Elevation info/perception is eliminated.
On Day 5 – 19, what did researchers find?
The Elevation perception returns despite still wearing the earplug
Around 20 days in, what did researchers find?
Around 20 days, the perception of Azimuth and Elevation has returned to approximately normal, they can judge both the Azimuth and Elevation pretty accurately.
What happened after the ear plug was removed?
The Elevation and Azimuth perception returns to pre-treatment levels immediately (new representation created, rather than plasticity).
What is the difference between the auditory system and the visual system when dealing with having their senses manipulated?
The auditory system seems to deal with changes to the shape of the ear by creating a whole new map, opposed to the visual system which slowly changes the existing map into something and slowly change it back afterwards.
Why were Barn owls selected as a model for studying the physiology of Sound Localization?
They were easy to handle, and ethologists noticed they could fly around in barns in the dark, and could catch the mice without seeing them.
What did researchers find when performing head-tracking studies performed on Barn Owls in complete darkness?
They were found to be remarkably accurate.
Barn Owls sound localize abilities were tested based on ___ and ___.
Azimuth // Elevation
Barn Owls use ___ To localize sounds in ___.
Interaural Time Differences // Azimuth
If there is an ongoing time disparity between the two earphones, when the disparity was positive, the owls would orient their heads as if the sound was coming from ___ Azimuth, in other words, they would turn their head to the right when the right ear was stimulated first. They would turn their heads to the left if the left ear was stimulated first.
positive
In the sound localization studies done on Barn Owls, there was a correlation between the ___ and the ___.
animals behaviour // Time Disparity/ITD
___ proposed that there were neurons that received input from both ears and acted as ___.
Jeffress (1948) // Coincidence Detectors
In an auditory Coincidence Detector, neurons require stimulation from ___ ear(s) to become activated, and it is the ___ along the axons/along the projections that will reach the ear at different times.
both // conduction velocity
In an auditory Coincidence Detector, if each one of the neurons is only activated by one branch it ___ fire, if the neuron is activated by two branches simultaneously, it ___ fire.
won’t // will
In an auditory Coincidence Detector, if a sound is coming directly from the front, where sound starts at the right and left ear at the same time, and they propagate along at the same time, the ___ neuron would become activated.
middle
In an auditory Coincidence Detector, if sound is coming from the Right, the signal propagating from the Right ear gets a head start, so it goes further along before the left ear even starts. What this does is it will shift the activation of the neurons to the __, so the 3rd on the left side becomes activated, because by the time the left ear and right ear are converging on the same neuron, its over on neuron 3.
left
Barn Owls have ___ coincidence detectors and narrowly tuned ___..
narrowly tuned // ITD neurons
When Barn Owls were examined with electrophysiological recordings, there were cells in the ___ which had these very narrow ITD specificities that are ___.
Mesencephalic Lateralis Dorsalis Nucleus (MLD) // space-specific
Barn Owls were found to have auditory receptive fields that respond strongly ___ degrees to the ___.
10 // right
Barn Owls have a very tight tuning for ___ because they have ___ skulls where one their ears points up and one points down, which allows them to use ITD for Elevation as well.
Elevation // asymmetrically-shaped
True or False: Mammals have narrowly-tuned ITD neurons in their brains
False, Mammals do not have narrowly tuned ITD neurons in their brains
Mammals have ___-tuned ITD neurons while Barn Owls have ___-tuned ITD neurons.
broadly // narrowly
Why are Gerbils often used to study Broadly-tuned ITD neurons?
Because they are quite good at auditory localization, but the principles have been found in other mammals including primates.
ITD neurons located in ___ of Gerbils and other mammals are much more ___. They respond to a range of ITDs that are ___ than what occurs in the natural environment.
Superior Olivary Nucleus // broadly tuned // greater
Broadly-tuned ITD neurons respond most to sound coming from the ___ side, so when looking at a neuron recorded from the left hemisphere of a, it responds best when sound leads from the ___ ear. The neuron responds best when there is a ___ difference between the left and right ears being stimulated.
Contralateral // right // 200 microsecond
How is it that these broadly-tuned neurons can lead to an accurate localization of sound along the Azimuth?
It’s thought that sound localization is based on a ratio of the two populations.
In Broadly Tuned ITD Neurons, if sound is coming from the center line, 0 Azimuth, the two populations would be ___ active. However, if sound info is coming from the right side, so that it would hit the right ear first, it would be detected by the ___ hemisphere neurons, and would produce much less activity in the ___ hemisphere neurons, it would produce a difference in the ratio of activity between the two curves. Anywhere you put the sound, the ratio would be ___ for that Azimuth.
equally // left // right // unique
Sound location = ___ of ___ populations
ratio // 2
The Binaural neurons coding for ITD are located in the ___.
Superior Olivary Nucleus
What is the journey from the ear to thee Medial Geniculate Nucleus?
Info coming from the Cochlea down the Cochlear nerve → hits the Cochlear nucleus → from there, it crosses the midline/decussates and so there is Ipsilateral and Contralateral projections to the Superior Olivary Nucleus, from then on, it is Binaural info coming from both ears reaching the inferior colliculus and the medial geniculate nucleus.
The way to remember the order of these structures is the acronym SONICMG.
SON = ___
IC = ___
MG = ___
Superior Olivary Nucleus // Inferior Colliculus // Medial Geniculate Nucleus
What is the Medial Geniculate Nucleus?
The Medial Geniculate Nucleus is a thalamic structure that processes auditory information.
It sounds like the LGN which processes visual info
What is the function of the Superior Colliculus?
The Superior Colliculus is important for visual orienting.
What is the function of the Inferior Colliculus?
The Inferior Colliculus is important for sound processing
Afferent processing is Binaural (2 ears) from the level of the ___ onwards.
superior olivary nucleus
There are ___ and ___ streams for hearing.
”What” // “Where”
In A1 the ___ stream starts in the anterior portion of the belt and extends to the ___ and then ___, this is used for sound ___.
“What”/Ventral // Temporal // prefrontal cortex // identification
In A1 the ___ stream starts in the posterior part of the belt and extends to the ___ and then sends projections to the ___, this is for auditory/sound ___.
“Where”/Dorsal // Parietal // prefrontal cortices // localization
Experiments done by Steve Lomber (UWO) demonstrate the separation of “what” info and “where” info in cat auditory cortex using ___.
Cryoloop inactivation
How does Cryoloop inactivation work?
Stainless steel pipes are overlaid on top of the cortex, and cold fluid passes through the pipes to cool down the brain. Cooling of the brain causes temporary inactivation, puts it to sleep temporarily, and when it rewarms, it acts normal.
Cryoloop inactivation is good for ___ tests, because it creates a lesion that is ___, so you can test an animal when a lesion is present and that region is inactivated, and when that area is normal and all the brain regions are functioning ___.
behaviour // temporary // normally
In Lomber’s Cryoloop inactivation tests, as a control, when the core primary auditory cortex (A1) was inactivated there was ___ sound localization.
poor
In Lomber’s Cryoloop inactivation tests, when the anterior/what region is inactivated, the cats cannot ___ sounds, but can still ___ sounds.
identify // locate
In Lomber’s Cryoloop inactivation tests, when the posterior/where region was inactivated, cats could not do the object ___ task, but could do the object ___ task.
localization // identification
This is very strong evidence for the ___ of what vs where information in the sound processing stream, which is complementary to the what vs where in the visual processing stream
double dissociation
For the visual system, Receptive field location and spatial organization is coded ___ due to the optics of the eye, and the ___ that is maintained throughout processing.
directly // retinotopic organization
In the visual system, things like ___ and ___ need to be calculated, it doesn’t mean that they are less important, it just means that there has to be more ___ dedicated to measuring those qualities about the visual input.
depth // motion // neural processing power
For Hearing, frequency is ___, but receptive field location is calculated from ___, ___, and ___.
coded directly // ITDs // ILDs // Spectral Cues
What are Spectral Cues?
In hearing, the distribution of frequencies reaching the ear that are associated with specific locations of a sound. The differences in frequencies are caused by interaction of sound with the listener’s head and pinnae.
