A METHOD FOR IDENTIFYING SHORT-LATENCY HUMAN COGNITIVE POTENTIALS IN SINGLE TRIALS BY SCALP MAPPING

Studies of scalp-recorded brain event-related potentials in humans cur rently depend on the electronic averaging of many responses to the sti mulus. In non-averaged single responses, it is sometimes possible to s ee late components such as the so-called P300, but not the shorter lat ency components that are much smaller and masked in background noise. We tried to identify short-latency cognitive potentials evoked by fing er stimulation by comparing single trial responses that are concomitan tly recorded at the contralateral and ipsilateral parietal scalp respe ctively. We developed a single trial topographic mapping method that p roved important for assessing whether any left-right difference at sho rt latency indeed reflected genuine cognitive electrogeneses. These re sults make it possible to analyze on a trial-by-trial basis the short latency cognitive processing in somatic perception.