Psychophysical and electrophysiologic support for a left hemisphere temporal processing advantage.

Objective: The objective of this study was to investigate cerebral asymmetries for the detection of brief temporal events in a group of 22 dextrals using psychophysical measures.

Background: By combining electrophysiologic and psychophysical measures, it should be possible to demonstrate that the right ear advantage reported in previous studies is the result of a left hemisphere temporal processing advantage rather than a rightward attentional bias.

Method: Bursts of white noise lasting 300 milliseconds were delivered unilaterally to the participants' ears. Half of the stimuli contained a gap lasting either 4 or 6 milliseconds. Participants indicated whether or not the noise burst contained a gap. Asymmetries in alpha and beta activity at left and right temporal lobe sites were measured during the task.

Results: The psychophysical data confirmed previous reports of faster response times (RTs) and lower levels of error for the right ear (RE). There was no asymmetry in alpha activity between the left and right temporal lobes; however, there was a higher level of beta activity in the left temporal lobe.

Conclusions: The electrophysiological data suggest that the perceptual asymmetry is not the result of a nonspecific rightward attentional bias but that of a left hemisphere specialization for the detection of brief temporal events. The relation between atypical temporal processing asymmetries and developmental learning disorders is discussed.