Delay modulates spectral correlates in the human EEG of non-verbal auditory working memory

Studies using neuroimaging and electro- and magnetoencephalographic techniques have begun to identify the brain structures and dynamics that underlie auditory working memory. However, past research has not clearly characterized how the neural dynamics varies with the delay over which auditory information must be maintained. We used electroencephalogram band power as a measure of relative neuronal synchrony during a non-verbal auditory working memory task. Comparing the working memory task with a control recognition task, the relative synchrony in bilateral theta and alpha bands was unchanged using a two second delay. However, five and ten second delays produced increases and decreases in relative synchrony, respectively. The memory task also induced greater synchronization in beta and gamma bands over the right temporal cortex during the two and five second delays. The results suggest that the cortical dynamics that underlie auditory working memory are highly dependent upon a duration-dependent encoding strategy. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.