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Abstract:
Most objects and events can be detected by more than one sensory system. Thus, to form a coherent percept of the environment the brain has to combine information from different senses. Multisensory integration of visual and auditory information offers numerous benefits for the accuracy or completeness of the perception and seems to depend on neural substrates that can be found at various levels of the cortical processing hierarchy. The objective of the current human fMRI study was to identify and characterize brain regions mediating the integration of invariant higher-order audio-visual features that specify complex natural objects. We presented subjects with tools and musical instruments as pictures and sounds whilst manipulating their relative informativeness with respect to object recognition and controlling for their low-level features. Subjects were engaged in a categorization or target detection task. Across both tasks, we show higher-level audio-visual interactions in posterior, middle and anterior por
tions of the superior temporal sulcus (STS), with those regions obeying the law of inverse effectiveness: integration effects were larger for less effective stimulus configurations. We demonstrate that these findings parallel indices of multisensory enhancement on the behavioral level. These results confirm the role of STS as a major convergence site of auditory and visual information and show that invariant higher-order audio-visual features are integrated within higher association areas of the brain.
