The name is absent

³⁸

2003), will be important to better understand the functional differences between the
Cytoarchitectonicsubdivisionsoftheoperculum.

Connections from many parietal regions to MST are considered to be "top-
down" in the neuroanatomical sense, because they receive feed forward projections
from MST and send feedback projections to MST, placing them higher in the visual
processing hierarchy than MST (Felleman and Van Essen 1991). Top down has a quite
different meaning in the psychological literature, in which it is used to describe
perceptual phenomena that have a strong cognitive component, as opposed to bottom-
up perceptual Processesthatarethedirectresultofsensoryinput. Although
somatosensory responses in MST may arise from perceptual processing (bottom-up in
the psychological sense), their potential substrates (e.g., VIP-to-MST feedback
projections) is neuroanatomically top-down. We separately consider cognitive and
perceptual processes that may be related to MST Vibrotactile responses without labeling
them as bottom-up or top-down.

The first cognitive factor that we consider is visual imagery. Previous studies
reporting tactile activation in MT+ have used complex stimuli (such as a brush stroking
the arm) and tasks (such as discriminating the direction of motion of a rotating sphere
by touch) likely to induce imagery of visual motion. In our experiment, the piezoelectric
vibrator was stationary relative to the body surface, so that there was no external cue to
evoke imagery of visual motion. Imagery of the body site of stimulation is another
possibility. In this view, tactile activation in MST is primarily an epiphenomenon of
imagining the visual appearance of the touch or the body part being touched. However,

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