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.