Are visual-auditory fusion limits valid estimations of spatial disparity uncertainty?
Poster Presentation

David Hartnagel
IMASSA - Université Paris 8

Alain Bichot
IMASSA

Corinne Roumes
IMASSA

     Abstract ID Number: 52
     Full text: Not available
     Last modified: May 30, 2007
     Presentation date: 07/06/2007 10:00 AM in Quad Maclauren Hall
     (View Schedule)

Abstract
Electrophysiological studies have shown that spatially coincident visual-auditory (VA) stimuli give rise to response enhancement in the Superior Colliculus (SC) cells whereas a response depression appears for a certain amount of stimuli disparity (Stein & Meredith, 1993). For humans, the unity perception of VA stimuli, called fusion, varies with spatial disparity (Godfroy et al., 2003). This fusion phenomenon could be a behavioral parallel to the multisensory integration found in the SC. Recent experiments showed that VA fusion varies with horizontal eccentricity and gaze shift (Hartnagel et al., 2005). This experiment used a broadband noise burst and a 1°, 500ms duration light spot, simultaneously presented with a random spatial disparity. Participants had to judge about their unity. Results have shown that VA fusion limits in azimuth varies with horizontal eccentricity of the bimodal stimulus. VA fusion limits were estimated by the Point of Subjective Equality of the fusion responses variation with VA disparity. To assess the accuracy of fusion limit estimation, response times (RT) were analyzed to assess the response uncertainty. Results showed that RTs vary with VA spatial disparity according to fusion thresholds estimation. An additional comparison between fusion limits analysis and signal detection analysis (d’) is discussed.