Coding interaural time differences for sound localisation - the steps beyond the initial binaural comparison

Summary

The project addresses the profound problem of how a representation of auditory space is derived in the brain. Specifically, we are asking how timing differences between the two ears are extracted neurally and used to pinpoint the horizontal position of a sound source.

Supervisor(s)

Dr Christine Koeppl

Research Location

Camperdown - School of Medical Sciences - Bosch Institute

Program Type

PHD

Synopsis

The localisation of sounds, a task that we subconsciously carry out many times a day, is not as easy as it seems. Unlike, e.g., the eye, the auditory receptor (the cochlea), contains no map-like projection of the environment that can simply be relayed to the brain. So how does the brain solve the problem of sound localisation? From behavioural tests, it is well known that humans and animals rely on subtle differences between the sound arriving at the two ears, so-called interaural differences, to reconstruct its spatial origin. Such differences arise from the head’s shadowing effects and influence both the time of arrival and the loudness of the sound. Interaural time differences are known to be an important cue for humans in the low-frequency range. Experiments in the barn owl, a nocturnal predator that is able to localise sounds very precisely, have led to a widely accepted model of the neural representation of interaural time differences. Recent results from small mammals (guinea pigs and gerbils), however, are incompatible with that and have resulted in an alternative model. It is now important to clarify which conditions select for one or the other coding strategy, in order to make predictions for the brain representation in humans who cannot be tested neurophysiologically. One suggestion is that head size and thus interaural distance and the resulting range of interaural time differences is very important. The PhD project will test this by comparing the small-headed chicken to the well-known neural circuitry of the barn owl. Specifically, we will focus on the processing steps following the initial binaural comparison.

Additional Information

Techniques will include in-vivo neurophysiology and neuroanatomical tracing. Relevant previous experience would be an advantage.

From 2010, the location of this reserach project will be the Department of Biology and Environmental Sciences, University of Oldenburg, Germany (http://www.biologie.uni-oldenburg.de/en/)

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Keywords

hearing problems, Sensory, Hearing, Auditory, Sound localisation, Evolution, Hearing & vision problems, Neuroscience & psychology, The senses, Human body

Opportunity ID

The opportunity ID for this research opportunity is: 20