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Cortical processing of interaural timing differences (ITDs) was investigated with event-related potential (ERP) measurements in 16 human participants who were required in separate tasks to detect or to spatially localize dichotically embedded pitches. ITDs elicited three ERP components labeled ORN, N2, and P400. The ORN occurred at a latency of 150-250 ms and was elicited by ITDs regardless of location or task. In contrast, the N2 response (250-350 ms) was strongly modulated by location and showed larger amplitudes for the localization task than for the detection task. Finally, ITDs in the detection task elicited a P400 at a latency of 400-500 ms, but this response was entirely absent from ERPs elicited by identical stimuli in the localization task. These results are consistent with a sequential model of auditory perception in which segregation of concurrent sounds is followed by domain-specific processing of object location and identity.

We investigated the role of cerebral motor structures during mental hand rotation. Neural activity was measured with event-related potentials (ERPs) in 16 healthy participants while they performed handedness judgments of visually presented hands. Mental rotation was associated with ERP amplitude modulations as early as 170 ms but most strongly during a time window of about 600–800 ms. Source analysis of ERPs during these time windows indicated generators in bilateral extrastriate and parietal cortices. The results do not support a direct involvement of anterior motor cortices in the neural computations underlying mental rotation. However, motor regions may play a role in providing ongoing kinaesthetic feedback during mental rotation or in checking the results of the imagined transformation.

When inverted, thatcherized faces appear normal. This may be due to a decrease in configural and an increase in featural processing. It is not known whether this processing is continuous or reflects two distinct processing systems. Using event-related potentials (ERPs), we investigated the Thatcher effect on thatcherized and normal faces at varying orientations. The ERPs paralleled the perceptual illusion. The effect of thatcherization on upright faces was visible in P1 and N170 ERP components, possibly reflecting attentional engagement due to unpleasantness of thatcherized faces. Effects were also found over two later components, the P250 component, which has been related to configural recognition, and a late parietal component possibly reflecting featural processing. The effect of thatcherization on the two later components decreased gradually (for the P250 component) and abruptly (for the late parietal component) as the faces were rotated away from the upright. Descriptors: Brain mapping, Electroencephalography, Face perception, Perceptual illusion, Visual event-related potentials

We recorded 128-channel EEG from 16 participants while they observed, imitated, and self-initiated the precision grip of a manipulandum. Mu rhythm amplitudes were significantly lower during observation of a precision grip than during observation of a simple hand extension without object interaction. Scalp topographies for subtractions of observation, imitation, and execution conditions from the control condition showed a high degree of congruence, supporting the notion of a human observation–execution matching system. Surface Laplacian transformations suggest that the decrease in mu amplitude during precision grip observation reflects desynchronization of mu rhythm generators in the sensorimotor cortex. These results support the hypothesis that sensorimotor cortex is a neural substrate involved in the representation of both self- and other-generated actions and show the mu rhythm is sensitive to subtle changes in observed motor behavior.