Topographical analysis of homotopic interhemispheric "relay" asymmetries in visual evoked potentials

Brown and colleagues (1994) found that most evoked potential studies provide evidence of faster interhemispheric relay from the right to the left hemisphere, as determined from N160 latencies derived from parietal and occipital electrode sites. The experiment reported here was designed to complement those findings by 1) analyzing more electrode sites (several frontal, temporal, and central sites in addition to the previously investigated sites) and more waveforms (P1 and P2 waves); 3) introducing analysis of amplitude data; 4) carrying out site-specific and experiment-wise inference tests of putative interhemispheric relay asymmetry. We found that all of the conclusions of Brown and colleagues, regarding latency effects, could be extended to the ensemble of electrode sites and waveforms. However, amplitude effects were significantly compatible with stronger (though slower) relay from the left to the right hemisphere.