Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Rachel Ege (Donders series 406)

4 November 2019

Promotor: prof. dr. J. van Opstal
Co-promotor: dr. M. van Wanrooij

Dealing with Uncertainty in Human Sound Localization

This thesis describes a series of psychophysical experiments that probe
some of the neural mechanisms underlying human sound-localization
behaviour. The focus lies on revealing the brain’s strategies to cope
with uncertainty about a sound’s location, which is due to inherently
incomplete information in the sensory input on the one hand, and to
internal and external noise sources on the other hand. A possible
strategy to reduce sound-location uncertainty is to integrate the
sensory observations with prior information.
In Chapter 2 we found that vertical and horizontal sound localization
mechanisms rely on different strategies to deal with spatial uncertainty
and that vertical sound localization appears to strongly rely on the
involvement of a (finite width) spatial prior. In Chapter 3 we tested
the extent to which self-derived spatial information about the
environment (spatial prior) is used during sound localization. In
Chapter 4 we studied whether a precedence effect (temporal prior) may
also exist for the elevation direction, which is extracted from the
acoustic input on the basis of very different cues than azimuth. In
Chapter 5, we investigated where in the auditory system the audiovisual
interactions might take place (audiovisual integration), by testing the
Ventriloquism aftereffect for a set of different frequencies, after
entraining a ventriloquist effect with a particular frequency.