The present study employed a combined CSD-PCA approach that is not subject to the interpretational ambiguities stemming from the recording reference or ERP component quantification, which may have contributed to prior conflicting reports concerning P3 asymmetry. Apart from this methodological advantage, the capability of these combined methods to separate task- and response-related effects for temporally and spatially overlapping components, which are highly blurred in volume-conducted surface potentials,28,34,76 allowed the identification of a late, left-lateralized source. This source was unique to silent-counting of targets and approximated the timing of the subjects’ manual response, suggesting an increased, left-lateralized memory load associated with updating the internal target count. Most importantly, this left-lateralized source was markedly reduced in patients, which is consistent with impairments of working memory in schizophrenia.77,78 The left temporoparietal topography of this silent-counting effect resembles topographic abnormalities observed in schizophrenia for the late parietal old/new effect, which is widely considered an electrophysiological correlate of conscious recollection.93 In three independent studies, we found largely preserved late positive old/new effects in patients over mid-parietal sites, but markedly reduced old/new effects over left lateral
