Week 8 Flashcards
Tinnitus
- perception of ringing sound in the ears
Objective tinnitus
An actual sound is produced in the ears.
This may be due to middle ear muscle spasms, spontaneous ** otoacoustic emissions ** (produced by inner ear), or vascular problems.
Subjective tinnitus
Experienced by the individual, usually in association with another disorder.
Most common with noise-induced hearing loss.
Associated with both conductive and sensineural hearing loss.
Cochlear Implants
How are they inserted?
Electrodes are inserted into the cochlea to electrically stimulate auditory nerve fibers along the basilar membrane’s tonotopic map.
What does the cochlear implant device include?
A microphone, sound processor, transmitter (outside), andreceiver (surgically implanted)
What does the cochlear impact do and what’s it effective for?
Overcomes damage to the hair cells, but not damage to the cochlear auditory nerves.
Very effective for speech perception if done early (by 12-18 months)
If someone ruptures their tympanic membrane, they will experience:
A. Conductive hearing loss
B. Sensineural hearing loss
C. Objective Tinnitus
D. Subjective tinnitus
A
Auditory nerve fibers synapse in a series of sub cortical structures:
- cochlear nucleus
- superior Oliver’s nucleus
- inferior colliculus
- medial geniculate nucleus
- auditory receiving area
The first cortical region to receive auditory information is in the ______
Temporal lobe
Primary Auditory Cortex (PAC or A1)
It is believed to have broadly ** tonotopic** organization, matching the structure established in the consoles. There are thought to be multiple tonotopic maps in auditory cortex [not neatly organized]
Is the medial geniculate nucleus tonotopic ally organized?
A. Yes, abs
B. Prob
C. No
Yes
In A1, different patches of cortex responds to different _____
Characteristic frequencies (CF)
Natural sounds include
Speech, laughter, animal sounds, musical instruments, and tools.
Tonotopic maps can be found in
A1 (core area)
Neurons respond better to low frequencies are on the ____ and those that respond best to high frequencies are on the ___.
Left; right
The auditory cortex appears
Hierarchically organized
- neural signals travel through the core (including A1), then belt, followed by the parables area.
Simple sounds
Pure tones
Cause activation in the core area
Belt and parabelt areas
Are preferentially activated in response to more complex stimuli (tones, voices) made up of many frequencies. B
Bender and Wang recorded from a cell just outside A1 and found that it responded to______ with the scene fundamental frequency.
Complex Tones
Such cells were called pitch neurons
Norman used fMRI to measure responses to complex tones perceived as pitch (100 Hz) and frequency, match noise.
- The noise stimulus contains all the frequencies, but wasn’t perceived as having a specific pitch.
- Areas in interior auditory cortex were more responsive to pitch.
Effect of training (experience dependent plasticity) on tonotopic maps:
- Monkeys were trained to discriminate between two frequencies near 2500 Hz.
- Trained monkeys showed tonotopic maps (in A1) within large areas with neurons that responded to 2500 Hz compared to untrained monkeys. Importantly, rthe monkeys were better at the task after training
Where or Dorsal Stream
Start in the posterior core and belt, and extends to the parietal and prefrontal corticosteroids.
- Responsible for locating sound.
What or ventral stream
Starts in the anterior portion of the core belt, and extends to the prefrontal cortex.
- Responsible for identifying sounds
Patient with temporal lobe damage has trouble ____ but can ____.
Recognizing sounds; localize.
Patient with parietal lobe damage can ____ but is very poor with ______
Recognizing sounds; localization
Auditory space
The area surrounding an observer, which includes sound signals
Auditory scene
The array of all sound sources in the environment
Auditory scene analysis
Process by which sound sources in the auditory scene are separated into individual perceptions.
- this does not happen at the cochlea since simultaneous sounds are together in the pattern of vibrations on the basilar membrane.
Simultaneous grouping
When multiple sound sources are simultaneously active how do we separate sources?
How is the singer separated from the guitar?
Sequential grouping
As sounds follow each other in time, how do we perceive them at staying together?
How does the melody produced by the keyboard stay group together?
Auditory grouping principles for simultaneous grouping
Location, unset, synchrony, timbre and pitch, harmonocity
Location
A single sound source tends to be at one location and to move continuously
Onset synchrony
Sound that start at different times are likely to come from different sources
Timbre and pitch
Sound with the same pitch or timbre are grouped together with the same distinct source
Example : flute trails belong to the flute while trumpet blares belong to the trumpet
Similarity?
Harmonicity
When we hear a harmonic series ( fundamental + harmonics) we infer that it can form a single source
Auditory grouping principles for sequential grouping
Similarity of pitch, proximity in time, auditory continuity, effect of experience
Search grouping allows us to perform auditory stream segregation based on attributions of different pitch and timing to multiple sources
Similarity of pitch
Consecutive sounds of similar pitch are associated with a single source and group together
Proximity in time
Sound that occur in rapid succession usually come from the same source
Proximity ?
auditory Continuity
Sounds that stay constant or change smoothly are usually from the same source
Good continuation ?
Effect of experience
Familiarity
Top down knowledge
Auditory space
Surrounds an observer and exists, wherever there are sound sources
Researchers study house sounds are Localized in space along three dimensions
Azimuth
Elevation
Distance
Azimuth
Position left to right
Elevation
Position up and down
Distance
 Distance from observer
Binaural
Using both ears
- Interaural time difference (ITD)
- Interaural level difference (ILD)
Monaural
Using one ear
- spectral cues and the head-related transfer function ( HRTF)
Binaural cues
Location cues based on the comparison of the signals received by the left and right ears.
Interaural time difference ITD
Difference between the times at which sound reach the two ears.
- when distance to each ear is the same, there are no differences in time.
- When does sources to the side of the observer, the times will differ.
- this cue is better for low frequency tones under 800 Hz
Interaural level difference IDL
Reduction in intensity occurs for high frequency sounds for the far ear ( pointed away from the source)
- The head casts an acoustic shadow, blocking (reflecting) and absorbing some of the high frequency pressure wave.
This effect doesn’t occur for low frequency sound. Works best about 800 Hz.
ILD is largest at locations _____
Farther to the side
ILD and ITD are not effective for detecting ______ in elevation.
Differences
How much cones of confusion are possible?
Infinite
Spectral cue
The information for location comes from the spectrum of frequencies
HRTF
Unique to each head.
Dependent and head affect the intensities of frequencies
Which auditory cue would be most useful for locating a low frequency coming from under your feet?
ITD, ILD, HRTF, ALL
C
Best for elevation
Neroli tuned ITD neurons
Respond to specific time differences only. One neuron gives a location. This is a form of specificity coding.
Broadly tuned ITD neurons
Respond to broad late range of time differences. Location is calculated from a range of neural responses. This is a form of distributed coding.
What is the first place for information from both ears is combined?
Superior olivary nucleus
Human echolocation (flash sonar)
Some blind individuals can train them selves to detect objects in the environment by producing clicking sound in listening to the echo.
They don’t see, but they can sense the location of an object
FMRI evidence suggests echolocation experts , blind since the very young, use striate cortex V1 to help represent the space. Extreme case of experience dependent plasticity.
