Lateral asymmetries of event-related potential slow waves

Lateral asymmetries of event-related potentials (ERPs) were measured during auditory temporal and spatial discrimination tasks. The temporal task required a discrimination of a difference in the duration of a binaural standard and a test stimulus presented to either the right or left ear and the spatial task required a discrimination of the apparent location of standard and test stimuli presented in either the right or left hemifield. ERPs of 27 right-handed adults were recorded to click stimuli in each task. Negative slow wave activity elicited by test stimuli in the temporal task was greater over the right compared to the left frontal site. Positive slow wave in the spatial task was greater over the left compared to the right at both frontal and parietal sites. Asymmetry of parietal slow wave was related to subject s perceptual asymmetry (difference in d accuracy scores for right and left hemifields), whereas asymmetry of frontal slow wave was not. Moreover lateral asymmetries of frontal and parietal slow waves differed with respect to the influence of hemifield of test stimulus and whether test stimuli were the same or different compared to the standard. It was concluded that asymmetries of frontal and parietal slow waves reflect different aspects of lateralized cognitive processing.