| |
Abstract:
Abstract: Considerable attention has focused on the relevance
of high-frequency neuronal activity. For example, thalamocortical
gamma band activity has been argued to provide a basis for the
integration of sensory information. If coherent activity in
specific frequency bands is associated with the functional
characteristics of each hemisphere (e.g. phonetic segmentation in
the left versus prosodic analysis in the right), then the relevant
frequency bands might be differentially salient in the two
hemispheres. We performed EEG and MEG recordings during
presentation of auditory stimuli of varying spectral complexity,
including (continuous) speech and ripples (auditory analogue of
visual gratings). The power ratios between spectral frequency bands
were computed, revealing pronounced asymmetries. In particular, the
gamma/theta ratio is different for left and right hemispheres, with
gamma activity being more pronounced in the left temporal areas.
The effect is robust: it is observed in EEG and MEG recordings, and
for simple and complex stimuli. The characteristics of the spectral
power ratios differ among conditions for the complex auditory
stimuli and differ between single-trial and averaged data,
suggesting the importance of analyzing both time-locked and
non-time-locked activity. These data are consistent with the view
that information is analyzed in specific frequency bands and
different time-scales in the hemispheres.
|
