Sources of somatic sensory input to auditory cortex in monkeys

Troy Hackett, Dept. Psychology, Vanderbilt University

Abstract
Convergent auditory and somatic sensory activity in auditory cortex has been observed in several physiological studies of humans and nonhuman primates. These interactions have been found in association areas such as caudomedial (CM) belt area of auditory cortex adjacent to the core area, A1, as well as in the core or other belt areas. Since distinct sources of auditory input contribute to variations in the auditory properties of these areas, it is likely that regional differences in somatic sensory input underlie differences in multisensory activity, as well. To determine potential sources somatic input to A1, CM and adjoining areas, parallel studies of their cortical and thalamic connections were conducted in marmoset and macaque monkeys. In both species, the results suggest that the retroinsular area (Ri), located in the fundus of the lateral sulcus, is the principal source of somatosensory input to CM. Additional strong inputs from numerous multisensory nuclei in the posterior thalamus may also contribute to somatic activation in CM. In contrast, A1 lacks significant inputs from Ri, and has relatively fewer inputs from multisensory thalamic nuclei. These findings are consistent with current physiological findings, and support the hypothesis that regional differences characterize multisensory activity in auditory cortex.

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