Spectral dissociation of lateralized pairs of brain rhythms

Abstract: Using high resolution spectral methods to uncover neuromarkers of social, cognitive and behavioral function, we have found that hemi-lateralized pairs of oscillations such as left and right occipital alpha, or left and right rolandic mu dissociate spectrally. That is, they show a shifted frequency distribution, with one member of the pair peaking at a slightly lower frequency than the other. To illustrate the phenomenon, we analyze EEG spatio-spectral patterns providing examples of dissociations in the 10Hz frequency band. Our observations suggest that homologous pairs of neuromarkers have distinct intrinsic frequencies and only transiently coordinate their oscillations into synchronous ensembles. On occasion, hemi-lateralized pairs are observed to blend into medial aggregates, leading to strongly coherent dynamics. We hypothesize that spectral dissociation plays a role in the balance of integration and segregation in the brain: separation of oscillations from homologous cortical areas allows them to function independently under certain circumstances, while preserving a potential for stronger interactions supported by structural and functional symmetries. As a method, spectral dissociation may be harnessed to better track the individual power of each member of a hemi-lateralized pair, and their respective time-courses. Resulting insights may shed light on the functional interaction between homologous cortices in studies of attention (alpha), e.g. during perceptual and social interaction tasks, and in studies of somatomotor processing (mu), e.g. in bimanual coordination and brain computer interfaces.