The involvement of ipsilateral temporoparietal cortex in tactile pattern working memory as reflected in beta event-related desynchronization.

Cortical oscillatory activity in various frequency bands has been shown to reflect working memory processes operating on visual and auditory stimulus information. Here we use magnetoencephalography to investigate cortical oscillatory activity related to working memory for tactile patterns. Right-handed subjects made same-different judgements on two dot patterns sequentially applied with a 3-s delay to the right middle fingertip. Spectral analysis revealed beta desynchronization (17+/-2.5 Hz) at contralateral postcentral and ipsilateral temporoparietal regions preceding and during the presentation of both tactile stimuli as well as during the early and late delay periods. Whereas contralateral beta desynchronization preceding tactile stimulation may reflect anticipation of incoming stimuli, ipsilateral beta desynchronization may underlie working memory maintenance of tactile patterns. The later hypothesis is supported by a significant positive correlation between subjects' performance and the amplitude of ipsilateral beta desynchronization 800 ms to 500 ms before the onset of the second pattern stimulus. Thus, our results suggest that ipsilateral temporoparietal cortex contributes to the maintenance of tactile pattern information in working memory.