Unisensory Processing Time and Neural Coactivation: The Redundant Signals Effect Revisited
Poster Presentation

Lynnette Leone
Department of Psychology North Dakota State University

Mark McCourt
Department of Psychology North Dakota State University

     Abstract ID Number: 107
     Full text: Not available
     Last modified: March 26, 2007
     Presentation date: 07/06/2007 10:00 AM in Quad Maclauren Hall
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Abstract
We examined the dependence of the audiovisual (AV) redundant signals effect (RSE) on the processing speed of the unisensory visual stimulus. Experiment 1 measured reaction times (RT) to an auditory stimulus (1 KHz tone), and to low (1 c/deg) and high (18 c/deg) frequency Gabor stimuli, comparing them to RTs to multisensory AV combinations across a range (300 ms) of AV stimulus onset asynchronies (SOA). Over the course of 100 trials the intensities of the A and V unisensory stimuli were titrated to ensure criterion response accuracy (d’ = 2). For RT, significant violations of Miller’s inequality (i.e., neural coactivation) occurred only at an AV SOA of zero. The range of RTs over which such violations occurred tracked mean RTs for the unisensory V stimuli. Experiment 2 replicated Experiment 1 except that only the low spatial frequency visual stimulus was used and stimulus contrast was tripled to produce enhanced visual discrimination (d’ = 3+) and faster RTs. Relative to Experiment 1, mean visual RT decreased by 117 ms, and AV SOAs producing RSEs expanded to include those for which the visual stimulus preceded the auditory stimulus by 100-200 ms. We discuss these results in the context of neural coactivation models.