The Steady State Visually Evoked Potential Topography and Vigilance

We report data which demonstrates a correlation between the magnitude of the Steady State Visually Evoked Potential (SSVEP) and visual vigilance. The SSVEP was recorded from 64 scalp sites and elicited by a 13 Hz uniform visual flicker presented while subjects undertook a visual vigilance task. Fifteen right-handed males were required to view three times a 180 second series of geometrical shapes; a continuous sequence of 60 squares, 60 circles and finally 60 squares. Just prior to the final trial subjects were asked to identify a target circle. A comparison of the last two trials indicated that the appearance of the target circle was associated with a transient SSVEP attenuation in the occipito-parietal and right pre-frontal regions. The same comparison indicated a pronounced SSVEP attenuation in the centro-parietal region peaking after the appearance of the circles. The distribution of the attenuation at the pre-frontal, centro-parietal and occipito-parietal regions was lateralised with the right hemisphere showing pronounced and long lasting effects. Aspects of normal brain function and dysfunction can be further explored using this novel technique.