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brain network, including parietal areas such as VIP, that transform Somatotopic touches
on the body surface to Spatiotopic coordinates. The second perceptual process that may
explain tactile activation in MST is sensorimotor integration. Temporary inactivation of
MST interferes with visually guided hand movements as well as smooth-pursuit eye
movements (Hg and Schumann 2007), and there are anatomical connections between
MST and hand motor areas (Marconi, et al. 2001). Our finding that MST responds more
strongly to hand than foot stimulation supports a link between MST and eye-hand
coordination (Whitney, et al. 2007). Integrating visual and tactile signals in MST may be
important for enabling the complex dynamics necessary to track and grasp a moving
object. A third perceptual process that may explain tactile responses in MST is
involvement in purely somatosensory processing. Just as MST is important for
perceiving the direction and speed of visual stimuli (Celebrini and Newsome 1995), it
may also be important for computing the direction and speed of tactile stimuli (Blake, et
al. 2004; Hagen, et al. 2002). Although our Vibrotactile stimuli were stationary relative to
the body surface, they vibrated at a high frequency perpendicular to the skin surface.
MT+ responds to visual flicker (Tootell, et al. 1995), which could be considered
analogous to stationary Vibrotactile stimulation. Therefore, responses in MST to simple
Vibrotactile stimulation do not rule out the involvement of MST in tactile motion
processing.
Activity in MT and MST may also be dependent on the behavioral task. Although
we did not observe MT activity in response to passive Vibrotactile stimulation, it is
possible that other kinds of tactile stimuli and tasks, such as direction discrimination of a