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These systematic effects of sound on touch perception may be a consequence of
neuronal interactions within and between several different brain areas. The
organization of the cerebral cortex is well-suited for integrating sound and touch
information since a) primary auditory cortex is adjacent to secondary somatosensory
areas, b) there are anatomical connections from somatosensory cortex into auditory
cortex (Schroeder, et al. 2001), c) functional imaging studies show common cortical
activation sites for auditory and somatosensory information (Beauchamp and Ro 2008;
Foxe, et al. 2002; Ozcan, et al. 2005; Schurmann, et al. 2006), and d) even Unisensory
cortex may be driven by different sensory modalities (Ghazanfar and Schroeder 2006;
Macaluso and Driver 2005). This anatomical proximity and functional interconnectivity
may provide the neural basis for the interactions between audition and touch measured
in these experiments; connections between nearby areas of cortex are more extensive
than connections between distant areas.
The interactions between the auditory and somatosensory systems may reflect a
special case of multisensory integration for information in peripersonal space. Previous
studies have shown that auditory-somatosensory interactions may be specific to
information around the body (Serino, et al. 2007), regardless of whether the
peripersonal auditory information comes from in front of or behind the subject (Fame
and Ladavas 2002; Zampini, et al. 2007). Since in our experiments the auditory
information was always presented through headphones or in peripersonal space, we
cannot assess whether the increases in sensitivity to somatosensory information would
also extend for auditory information in far, extrapersonal space. Further experiments