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Experiment 2
In Experiment 1, subjects performed a discrimination task, manually pressing a
button in response to each sensory stimulus. It could be argued that the observed STS
activations were the result of cognitive processes involved in task performance, rather
than simple sensory responses. To address this possibility, in Experiment 2 subjects
received somatosensory Vibrotactile stimulation on their hands and feet that did not
require a behavioral response (Beauchamp, et al. 2007).
Because tactile stimuli were delivered bilaterally, we expected responses to be
evoked in both left and right hemispheres. Consistent with this, we observed activation
in the left and right postcentral gyrus, parietal operculum and STS (Fig. ЗА). Localizers
were used to map auditory and visually-responsive brain regions. Auditory responses
were observed in the temporal plane, inferior frontal cortex, and the STS (Fig. 3B) while
visual responses were found primarily in the occipital lobe and the STS. A conjunction
analysis revealed a focus Oftrisensory activation in posterior STS in the single subject
(Fig. 3D) and group average activation maps (Fig. 3E). The center-pf-mass of the average
STS activation was (56,41,14) in the right hemisphere and (-44,35,13) in the left
hemisphere.