Task 8: Auditory Localization Flashcards
Auditory localization
Locating of sound sources in auditory space.
Name the 2 dimensions in which sounds can be located in addition to distance
- azimuth = left to right
2. elevation = up to down
Name the 2 cues for localization
- binaural
2. monaural
Binaural cues
- define
- name 2 examples
Uses information reaching both ears to determine azimuth of sounds e.g. ITD + ILD
Interaural time difference (binaural cue)
Difference between when sound reaches left ear and when it reaches right ear. Provides information about location of low-frequency sounds.
-> ITD becomes larger as sources are located more to the side. When distance is equal, ITD is equal
Interaural level difference (binaural cue)
Difference in sound pressure level of sound reaching two ears.
- Acoustic shadow: reduces intensity of sounds reaching far ear.
- Reduction of intensity occurs only for high-frequency sounds because if object is larger than distance between waves, it has higher effect than if object is smaller.
Cone of confusion
Time and level differences provide info that enables us to judge location along azimuth, but they provide little info about elevation of sound source.
Monaural cue
one ear to determine elevation
Define spectral cue
Information for localization is contained in differences in distribution (spectrum) of frequencies reaching each ear from different locations
- best for judging elevation at high frequencies
Directional transfer function
Explains how head, pinna and ear canal change intensity of sounds with different frequencies arriving at each ear from different locations in space (azimuth and elevation).
Superior olivary nucleus
place where signals from left and right ears meet
Inferior colliculus
place where further binaural processing occurs
A1
signal arrive here, travel to other cortical auditory areas (core, belt and parabelt areas)
What do neurons of the belt area do?
provide more precise information than A1 neurons about location of sound sources
Jeffress neural conicidence model of auditory localization
model that proposes that neurons are wired so they each receive signals from two ears (blue is left ear and red is right)
Coincidence detectors
Neurons that only fire when both signals coincide by arriving at same time at neuron.
ITD tuning curves
Curve that plots neuron’s firing rate against ITD. Useful to measure properties of ITD neurons, because each respond best to certain ITD.
What kind of neurons is coding for localization based on? Where are they? What does the amount of firing indicated
- Broadly tuned neurons
- Right hemisphere when responding to sound on left and vice versa
- How much these neurons fire indicates the location of sound. If sound is in left side, right hemispheric neurons respond faster
Distributed code
Code of localization for mammals because ITD is determined by firing of many broadly tuned neurons working together.
Name the 2 auditory pathways extending from temporal to frontal lobe
What and where
What pathway
- location
- responsibility
- neurons
- effect of deactivation
- Anterior part of core and belt and extends to prefrontal cortex
- Responsible for identifying different types of sounds.
- Neurons in anterior belt respond to more complex sounds.
- Deactivating disrupts ability to distinguish two patterns of sounds
Where pathway
- location
- responsibility
- neurons
- effect of deactivation
- Posterior part of core and belt and extends to prefrontal cortex.
- Associated with locating sounds.
- Neurons in posterior belt have better spatial tuning than those in A1.
- Deactivating disrupts ability to localize sounds
Sound waves from all sound sources in environment are summed into ______ But our auditory system can distinguish events or objects
single complex wave
Auditory scene analysis
Process by multiple sound sources in auditory scene are separated into sound images.