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areas (including the STS) and the temporal plane, the location of core and belt areas of
auditory cortex (Fig. 2B). The visual Iocalizer activated occipital, temporal and parietal
cortex, including the STS (Fig. 2C). To determine regions that responded to all three
modalities, we performed a voxel-by-voxel conjunction analysis. Voxels concentrated in
the parietal lobe and the STS were active in all three conditions (Fig. 2D). The mixed-
effects group map showed a similar pattern, with a region of posterior STS responding
to all three modalities (Fig. 2E). The center-of-mass of the STS activation in the group
map was (52,44,15).
After identifying STSms, we measured the degree of multisensory integration in
STSms between tactile and auditory modalities. The evoked response in STSms to
unisensory and multisensory trials Was computed in each subject and averaged across
subjects (Figs. 2F, G). The response resembled a classical hemodynamic response with a
sharp increase followed by a slow return to baseline. Due to the relatively long TR (2.75
s), the largest magnitude of response was observed in the second TR, 5.5 s following
Stimulusonsetjthispeakmagnitudewasusedasameasureoftheamplitudeof
response in different trials. Because the STSms was defined without reference to the
multisensory response, unbiased statistical comparisons could be performed between
multisensory and unisensory responses (Simmons, et al. 2007).
The response was similar in unisensory tactile and auditory trials (0.30% vs.
0.31%±0.02% SEM for both). In multisensory tactile-auditory trials, the response was
significantly larger than the maximum unisensory response and the average unisensory
response (multisensory response, 0.38%±0.02%SEM vs. max Unisensory response,