Lecture 19 Flashcards
Describe neural frequency tuning curves
Pure tones can be used to determine the threshold for specific frequencies
measured at single neurons, which can then be used to produce neural
frequency tuning curves
Describe characteristic frequency
Frequency to which the neuron is most
sensitive
Describe the cochlear amplifier
the entire outer hair cells
respond to sound by slight tilting and a
change in length
* These cells are referred to as the
cochlear amplifier
Describe the importance of cochlear amplifiers
- Damage to the outer hair cells impacts
the frequency tuning curve,
demonstrating the role they play when
intact - Higher threshold = lower sensitivity =
worse hearing
Describe place theory
Place theory suggests that pitch perception is based on the relation between
a sound’s frequency and the place along the basilar membrane that is
activated
Describe the effect of the missing fundamental
The ‘effect of the missing fundamental’
could be explained by assuming the
harmonics also vibrate the membrane, and
that the spacing of the intervals is
informative of the fundamental
Describe resolved harmonics
The lower harmonics produced by tones
tend to create distinct neural responses
What are unresolved harmonics?
In contrast, higher harmonics tend to create
neural responses that are not clearly
distinguishable
What is another name for the repetition rate?
the interval spacing
Describe phase locking
carries similar temporal information that may assist
with pitch perception
Name the places that the auditory nerve signal travels to
- The auditory nerve sends signals generated
in the cochlea to various subcortical
structures while en route to primary auditory
cortex, including: - Cochlear nucleus
- Superior olivary nucleus (brain stem)
- Inferior colliculus (midbrain)
- Medial geniculate nucleus (thalamus)
- Acronym: SONIC MG
Describe the primary auditory cortex
(auditory
receiving area, or A1, in temporal
lobe) can be divided up into three
general subregions:
* Core area
* Belt area
* Parabelt area
Describe pitch neurons
respond to the same fundamental frequency,
regardless of what harmonic is heard
Describe anterior auditory cortex
Evidence for a greater responses to pitch information
Describe noise induced hearing loss
Acute
exposure to very loud noises can severely
damage the hair cells in the organ of Corti
Describe hidden hearing loss
situations in which individuals may have normal results
(e.g. thresholds) in a standard hearing test using pure tones played in isolation, yet
have difficulty perceiving more complex ‘real-word’ sounds
Describe presbycusis
Results from the cumulative effects of exposure to noise over time
- Greatest loss at high frequencies
- Affects males more severely than females
- Can be caused by exposure to some drugs (which damage the hair cells)
Describe auditory localization
- Locating sounds in space
Describe azimuth coordinates
left to right position
Describe elevation coordinates
up and down position
Describe distance coordinates
position relative to observer
Describe location cues
created based on how sound waves interact with our
head/ears
Describe binaural cues
location cues based on the comparison of the signals
received by the left and right ears (interaural time and level differences) to
determine the azimuth (i.e. left-right) position of sounds
Describe interaural level difference
a binaural cue related to differences in
sound pressure levels reaching each ear
Describe acoustic shadows
- Reduction in intensity occurs for high frequency sounds for the far (relative to
audio source) ear, due to the head casting an acoustic shadow - This effect does not occur for low frequency sounds
because the distance, or spacing, between waves
(i.e. frequency) for low frequency sounds is relatively
large, in comparison to the object casting the
acoustic shadow (i.e. your head)
Describe intraural time difference
a binaural cue
related to differences in the timing of when a sound
reaches each ear
* When distance to each ear is the same, there is no
difference in timing (ITD = 0)
* When the source is to the side of the observer, the
times will differ
* Behavioural experiments show that ITD is most
effective for localizing low frequency sounds
Describe cone of confusion
(many) conical
space(s) around the ears for which various
possible pairs of points on an ‘imaginary cone’
would produce the same ITD and ILD
Describe monaural cues
location cues based on signals reaching a single ear
Describe spectral cues
The monaural cue we primarily rely on is referred to as a spectral cue, because it
involve using information related to the distribution of intensities of a particular
spectrum of frequencies experienced
Describe frequency spectra study
Frequency spectra recorded by a microphone placed inside the ear for the
same stimulus being played at different elevations
