Current source density analysis of CNV during temporal Gap paradigm

The present report studied the contingent negative variation during Gap and Non-Gap conditions using visual stimulation and manual responses. The reac tion times during the Gap condition were facilitated compared with those of the Non-Gap condition. The contingent negative variation component was obt ained during the preparatory period from electrodes placed at 58 scalp site s for both Gap and Non-Gap conditions. The comparison between both conditio ns: Gap and non-gap did not show statistically significant differences duri ng the preparatory period. The topography of the voltage and current source density maps showed three different foci: (i) an early negativity centred in electrodes overlying the supplementary motor area and cingulate motor ar eas, (ii) an activation over the primary motor cortex contralateral to the finger movement, and (iii) a bilateral activation on posterior sites. All t hese results suggest that the facilitation induced by the warning stimuli o ccurs in neural circuits that would be recruited for the subsequent process ing of the imperative stimulus. The facilitation of the reaction times duri ng the gap condition with respect to non-gap condition must be justified by neural events occurring during the gap period.