Fig. 3 illustrates the scalp field potentials (nose-referenced ERP) and CSD topographies at the peak latency of N1 produced to a number of different auditory stimuli. All nose-referenced ERP topographies show the distributed, midline-frontal negativity described for N1/P2 by Vaughan and Ritter (1970). The corresponding CSD topographies are readily distinguished from the corresponding ERP topographies by their regional specificity and the absence of a midline maximum. In place of a midline topography, the auditory N1 CSD includes sinks immediately anterior to, and sources posterior to, the Sylvian fissure, aligned in proximity to primary auditory cortex. This generator pattern is repeatedly obtained for frequent nontargets and distractors in various auditory oddball tasks, but is readily distinguishable from that of a slightly later, overlapping pattern of activity identified with sinks over the lateral surface of the temporal lobe (temporal N1; Kayser and Tenke, 2006a; Tenke et al., 1998, 2008, 2010).
