Transcallosal conduction time measured by visual hemifield stimulation with face images.

Transcallosal conduction time (TCT) in human visual system was estimated from the hemispheric difference of the peak latencies of face-evoked magnetic field (N170m) by left/right hemifield stimulation using 14 8 channel whole-head magnetometers. The estimated TCTwas 18.0 + 6.2 ms (mean +/- s.d.). Although N 170m amplitude was larger in the right hemisphere of seven of nine subjects, no hemispheric asymmetry was observed in the TCT estimate. Transcallosal visual information was likely to be transferred in the higher order (non-retinotopic) visual cortices. Hemifield stimulation with face images is a useful non-invasive method to estimate the TCT in human visual system.