TOPOGRAPHIC DIFFERENCES OF SLOW EVENT-RELATED BRAIN POTENTIALS IN BLIND AND SIGHTED ADULT HUMAN-SUBJECTS DURING HAPTIC MENTAL ROTATION

Twelve blindfolded sighted, nine congenitally blind, and seven adventi tiously blind subjects were tested in a haptic mental rotation task wh ile slow event-related brain potentials in the EEG were recorded from 17 scalp locations. The overall topography of the slow wave pattern wh ich prevailed during the task differed for sighted and for blind, but not for congenitally and adventitiously blind subjects. While the tact ile stimuli were encoded, the blind showed a pronounced occipital and the sighted a pronounced frontal activation. The task-specific amplitu de increment of a negative slow wave which can be understood as a mani festation of the process of mental rotation proper, showed a different topography for sighted and for blind subjects too. It had its maximum over central to parietal cortical areas in both groups, but it extend ed more towards occipital regions in the blind. In both groups, the ef fects were very similar to those observed in former studies with visua l versions of the mental rotation task, i.e. the slow wave amplitude o ver central to parietal areas increased monotonously with an increasin g angular disparity of the two stimuli to be compared. These results a re discussed with respect to the question of whether visual deprivatio n in the blind can cause a reorganization of cortical representational maps.