Early Visual Area Activation in Tactile Processing
Poster Presentation

Lotfi Merabet
Neurology, Harvard Medical School

Jascha Swisher
Psychology, Boston U

Stephanie McMains
Psychology, Boston U

Mark Halko
Psychology, Boston U

Amir Amedi
Neurology, Harvard Medical School

Alvaro Pascual-Leone
Neurology, Harvard Medical School

David Somers
Psychology, Boston U

     Abstract ID Number: 34
     Full text: Not available
     Last modified: March 14, 2005

Abstract
The contribution of early visual areas in tactile cross-modal sensory processing remains unclear. In a previous study, we employed rTMS to selectively disrupt somatosensory and occipital cortex processing while blindfolded sighted subjects performed a tactile task. Using arrays of raised dots of different inter-dot spacing, normally sighted subjects (blindfolded) were asked to rate the roughness and distance spacing between dot patterns presented in random order. rTMS delivered to somatosensory cortex impaired the overall perceived roughness while rTMS applied to the occipital cortex did not affect roughness but rather disrupted distance perception. As a follow-up to this study, we employed fMRI to investigate the contribution of early visual areas while subjects performed the same tactile task. Occipital cortex activation was evident in both hemispheres and for both roughness and distance determinations. Further ROI analysis revealed that activation was localized to V1 and that higher visual areas exhibited a pattern of progressive deactivation. Taken together, these results suggest that tactile discrimination implicates a network involving both somatosensory and visual cortical areas. Current studies are now investigating activation of V1 as a function of task difficulty and the role of this area in congenitally blind subjects.