Abstract
.Toward the goal of understanding cutaneous sensory integration during manual behavior, we used voltage-sensitive dye (VSD) imaging to study the organization and dynamics of anesthetized monkey primary somatosensory cortex (SI) in response to single and multidigit tactile stimulation. We find that in both macaque and squirrel monkey SI, VSD reveals clear focal digit topography consistent with previous electrophysiological and intrinsic signal imaging studies. VSD also reveals interactions in SI in response to multidigit stimulation. With a tactile funneling paradigm in areas 3b and 1 in squirrel monkeys, VSD reveals two-digit induction of subthreshhold influences, consistent with lateral intracortical inhibition. In response to tactile apparent motion stimuli, VSD reveals preferential response to motion stimuli over static tactile stimuli in both areas 1 and 3b. Comparison of the response at different digit locations to “toward digit” stimuli suggests the presence of direction-selective response in area 1; however, further study is needed. These exciting results indicate that VSD constitutes a powerful tool for studying somatosensory cortical processing in nonhuman primates and should be further developed for future somatosensory studies in awake behaving monkeys.
Highlights
Voltage-sensitive dyes (VSDs) are ideal for revealing the spatiotemporal patterns of cortical population response at mesoscales (50 to 100-μm resolution) and high temporal resolution
VSD staining of cortex was achieved by minipump infusion of VSD over 1.5 to 2 h through a tube attached to a piece of artificial dura (TecoflexTM) that covered the cortex [Figs. 1(d) and 1(e)]
We report that VSD imaging is a very useful tool for studying activation in monkey SI in response to cutaneous stimuli
Summary
Voltage-sensitive dyes (VSDs) are ideal for revealing the spatiotemporal patterns of cortical population response at mesoscales (50 to 100-μm resolution) and high temporal resolution (millisecond) This has proven enormously useful for studying the dynamics of cortical activity in both anesthetized and awake monkeys.[1,2,3,4] In the visual cortex, VSD has revealed spatiotemporal organization of retinotopic activation,[5] stimulus-induced traveling waves,[6] motion processing[7] (in cat), binocular integration,[8] contour integration and shape,[9,10] and color encoding.[11] VSD imaging has been highly instrumental for extending our understanding of visual feature representation and integration in monkey visual cortex. Understanding the pattern and dynamics of cutaneous inputs from the hand during such manual behavior is lacking and is crucial for designing manual prosthetics.[12,13] Previous work predicts that somatosensory cortical networks underlying different manual grasps are dynamic and reconfigure based on the type of grasp being performed.[14,15] In our studies, based on evidence from resting state fMRI connectivity, electrophysiological spike
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