Fine-grained tactile perception recruits early visual cortex in normally sighted humans
Single Paper Presentation

Krish Sathian
Department of Neurology, Emory University School of Medicine, Atlanta, GA, USA

Randall Stilla
Department of Neurology, Emory University School of Medicine, Atlanta, GA, USA

Erica Mariola
Department of Neurology, Emory University School of Medicine, Atlanta, GA, USA

     Abstract ID Number: 128
     Full text: Not available
     Last modified: March 17, 2006
     Presentation date: 06/20/2006 4:30 PM in Hamilton Building, McNeil Theatre
     (View Schedule)

Abstract
It is now accepted that extrastriate visual cortex is involved in touch in sighted humans. However, cross-modal activity in striate cortex (V1) is thought to occur only in the blind. In two separate fMRI studies, we have found cross-modal activity in or near V1 of normally sighted subjects. The first study contrasted shape and texture, perceived both haptically and visually. Bisensory texture-selectivity was found in medial occipital cortex near the calcarine fissure. In the second study, subjects were trained to tactually discriminate the direction of spatial offset of a central dot in a linear 3-dot array. Training progressively decreased the discrimination threshold, expressed in terms of the magnitude of offset required for 75% accuracy, well into the hyperacuity range (<1mm). Subjects underwent fMRI scanning before and after training on this experimental task; the scans included the experimental (spatial) task and a control (temporal) task. The task-by-session interaction revealed training-specific effects in medial occipital cortex, determined by retinotopic mapping in some subjects to be within V1 or V2. Thus, much of visual cortex, including V1, appears to have multisensory functions. Recruitment of cortex in or near V1 may occur in tactile tasks demanding particularly high spatial resolution.