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Abstract:
Abstract: We examined somato-auditory (S-A) interactions in
humans using high-density (64 channel) mapping of SEPs and AEPs
evoked by unilateral median nerve electrical and auditory stimuli,
alone, and in either congruent (ipsilateral) or incongruent
(crossed) combinations. S-A interaction, indexed by the difference
between the combined congruent S-AEP and the sum of the separate
SEP and AEP, was significant from ~50-100ms post-stimulus. Thus,
S-A integration appears to begin very early in cortical processing.
Scalp current density maps of the difference potentials were
consistent with both somatosensory and auditory cortical
contributions to the integration effects. The auditory cortical
contribution was supported by the demonstration of somatosensory
input to auditory association cortices in the superior temporal
plane posterior to A1 in macaque monkeys. As indexed by
multielectrode sampling of laminar current source density (CSD),
and multiunit activity (MUA) patterns, both auditory and
somatosensory stimulation produced laminar activation profiles
consistent with "feed forward" inputs, with an initial response in
layer 4, followed by infragranular and supragranular activation.
Our findings indicate that cross-modal convergence which underlies
multisensory integration begins early in cortical processing in
areas considered to be classically auditory in function.
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