Electrophysiological evidence of enhanced cortical activity in the human brain during visual curve tracing

ERPs were recorded while participants performed a curve tracing task in which they had to identify the end point of a target curve presented among three other distractor curves. Differential activation associated with the side of the target curve was found in the form of a sustained posterior contralateral negativity (SPCN). This contralateral brain activity suggests covert attention was deployed to the target curve during performance of the tracing task. The amplitude of the SPCN varied according to the hypothesized curve-tracing process, depending on whether the start and end locations of the target curve were above to below the horizontal midline, or the opposite, and this detailed analysis of the results provided evidence supporting the spread-of-attention model of curve tracing. These results represent the first neurophysiological investigation of brain activity reflecting visual curve tracing in humans.