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Sophie Wuerger, Markus Hofbauer, Georg Meyer; The integration of auditory and visual motion is not direction selective. Journal of Vision 2002;2(7):663. doi: https://doi.org/10.1167/2.7.663.
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There is evidence that visual and auditory signals are integrated at a perceptual level and in spatial attention tasks. In this study we investigated whether the subthreshold integration of visual and auditory motion signals depends on the direction of the motion signals in the two modalities.
The visual motion stimulus consisted of a random dot kinematogram (RDK) extending over 25 degrees of visual angle. A certain percentage of the dots moved in the same direction whereas the remaining dots moved in random directions. The RDK was presented for only 175 ms to minimise eye movements. The auditory stimulus consisted of two components, a noise pedestal which was different for each loudspeaker, and an incremental noise component that was cross-faded between the two loudspeakers, giving rise to a motion percept. The visual and the auditory motion had matched speeds of 10 degrees per second. The motion signals were either to the right or to the left. Auditory and visual motion directions could either be consistent (both to the left or both to the right), or inconsistent (one to the left, the other to the right). In each trial, two intervals were presented. One interval contained the noise stimulus (neither auditory nor visual motion); in the other interval the signal was present which was defined as either visual, auditory, or motion in both modalities. The task of the observer was to identify which interval contained motion.
Motion detection thresholds were defined as the coherence level at which the motion was detected with a probability of 0.81. For each of the two conditions (consistent and inconsistent motion) we fitted two-dimensional psychometric functions and estimated the motion thresholds. We find that the thresholds for inconsistent and consistent auditory and visual motions are very similar. This suggests that the integration of auditory and visual motion signals is not direction-selective.
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