A Source Analysis of the Late Human Auditory Evoked Potentials

Abstract

The intracerebral generators of the human auditory evoked potentials were estimated using dipole source analysis of 14-channel scalp recordings. The response to a 400-msec toneburst presented every 0.9 sec could be explained by three major dipole sources in each temporal lobe. The first was a vertically oriented dipole located on the supratemporal plane in or near the auditory koniocortex. This contributed to the scalp-recorded N1 wave at 100 msec. The second was a vertically oriented dipole source located on the supratemporal plane somewhat anterior to the first. This contributed to both the Nl and the sustained potential (SP). The third was a laterally oriented dipole source that perhaps originated in the magnopyramidal temporal field. This contributed a negative wave to the lateral scalp recordings at the latency of 145 msec. A change in the frequency of the toneburst elicited an additional negativity in the scalp-recording -the mismatch negativity (MMN). When the frequency change was large, the mismatch negativity was composed of two distinct sources with sequential but partially overlapping activities. The earlier corresponded to the Nl dipole sources and the later to a more anteriorly located dipole with an orientation more lateral than Nl. Only the later source was active when the frequency change was small. MMN source activities peaked about 15 msec earlier in the contralateral hemisphere, while this difference was only 4 msec for the sources of the Nl.

Knowledge of sequence structure prevents auditory distraction: An ERP study

“…participants were reading during tone presentation), in a tone sequence in which every fifth tone was a deviant, deviants did not elicit an MMN, presumably, because the unit of representation was not the single tone, but the five-tone micro-sequence. The lack of MMN elicitation depended, however, on the rate of presentation: MMN was not present when the onsetto-onset interval (stimulus onset asynchrony -SOA) was 100 ms, but a clear MMN was elicited when it was 1300 ms (see also Scherg et al, 1989). In a further study (Sussman et al, 2002), in which tones were presented with an SOA of 1000 ms, and participants actively monitored whether the repeating five-tone-pattern was violated, no significant MMN was observed.…”

Cortical Evoked Response to Gaps in Noise: Within-Channel and Across-Channel Conditions

“…The N1 component is thought to reflect stimulus characteristics such as intensity and timing (Naatanen & Picton, 1987), and may be generated by activity in the superior temporal plane as well as other sources in the temporal and frontal lobes (Knight, Scabini, Woods, & Clayworth, 1988; Papanicolaou, Bau-mann, Rogers, Saydjari, Amparo, & Eisenberg, 1990;Scherg, Vajsar, & Picton, 1989). The P2 component also appears to be affected by stimulus characteristics such as frequency and intensity (Hegerl & Juckel, 1993;Hillyard & Picton, 1987;Novak, Ritter, & Vaughan, 1992), and has sources in the primary and secondary auditory cortices that may or may not be distinct from those of the N1 (Knight, et al, 1988;Zouridakis, Simos, & Papanicolaou, 1998).…”

Neurophysiological evidence for context-dependent encoding of sensory input in human auditory cortex

“…The main neural generators of the MMN are located bilaterally in the supratemporal plane, as determined by dipole-modeling of electric (Scherg et al, 1989) and magnetic responses (Sams and Hari, 1991;Woldorff et al, 1998), scalp-current density maps of scalp-recorded ERPs (Giard et al, 1990), functional magnetic resonance imaging (fMRI) (Opitz et al, 1999(Opitz et al, , 2005, and intracortical ERP recordings (Halgren et al, 1995;Kropotov et al, 1995Kropotov et al, , 2000. The location of the generators in auditory cortex accounts for the observed scalp topography of the waveform, which is maximally negative over the frontocentral scalp locations and often inverts in polarity below the Sylvian fissure.…”