Electrophysiological evidence for fast visual processing through the humankoniocellular pathway when stimuli move

There is increasing evidence from cellular recordings in primates and behav ioral studies in humans that motion can be processed by other than the magn ocellular (M) pathway and the cortical dorsal stream. Little is known about cortical processing of moving stimuli when the information is conveyed by the third retinogeniculocortical pathway - the so-called koniocellular (K) pathway. We addressed this issue in humans by studying the spatio-temporal dynamics of the brain electrical fields evoked by tritan (S-cone isolating) and luminance-defined moving stimuli. Tritan and luminance stimuli are pre sumably carried by the K and M pathways respectively. We found two time int ervals where significant stimulus-specific electric fields were evoked: an early period between 40 and 75 ms after stimulus onset, and a later period between 175 and 240 ms. Some of these fields were identical for tritan- and luminance-motion, suggesting that the processing of moving stimuli share c ommon cortical substrates when mediated via K and M pathway input. However. tritan-motion stimuli also evoked unique electric fields that appeared ear lier in time than the common motion-specific fields, indicating very fast a ctivation of cortical areas specific to input through the K pathway. A dist ributed source localization procedure revealed simultaneous activation of s triate and extrastriate areas even at the early processing stages, strongly suggesting a very fast activation of the visual cerebral network.