Functional dissociation of brain rhythms in social coordination

ObjectivesThe goal of this research was to investigate sub-band modulations in the mu domain in dyads performing different social coordination tasks.MethodsDyads of subjects performed rhythmic finger movement under three different task conditions: intrinsic - maintain self-produced movement while ignoring their partner's movement; in-phase - synchronize with partner; and anti-phase - maintain syncopation with partner. Movement profiles of the dyads were used to estimate a synchronization index (SI) to verify differences in coordination according to each task. EEG was recorded during task performance and at baseline (partner's actions hidden from view). Log power ratios of mu band activity (active against baseline) were used to assess the relative levels of synchronization/de-synchronization in both the upper and lower mu bands.ResultsResults confirm a functional dissociation of lower (8-10 Hz) and upper (10-12 Hz) mu bands in social coordination tasks. Lower mu band activity was independent of specific modulations across tasks and hemispheric preferences. Upper mu band activity was sensitive to coordination tasks and exhibited marked differences between the hemispheres. Accentuated de-synchronization of right relative to left hemisphere in the anti-phase task appeared related to the greater demand of perceptual-motor discrimination. Left hemisphere de-synchronization in both in-phase and anti-phase coordination was interpreted in terms of successful production of imitation. Right hemisphere synchronization in the intrinsic task was interpreted as inhibition of an imitative response tendency.ConclusionsFunctional dissociation of lower and upper mu band and hemispheric preferences exists in real-time social coordination.SignificanceThis research attests to the merit of analyzing sub-band activity in the alpha-mu domain in order to identify neural correlates of social coordination. Such 'neuromarkers' may be relevant for brain disorders such as apraxia and autism.

► Spectral separation of sub-bands in the mu domain was used to identify neural processes in tasks requiring real-time social interaction: changes in the lower mu band were diffuse and non-specific; changes in the upper mu band were highly related to coupling measures of intentional social coordination. ► In the upper mu-band event-related synchronization was associated with uncoupled behavior whereas event-related de-synchronization denoted coupled behaviors. ► Coupled coordinated behavior displayed clear hemisphere predispositions: L > R in the in-phase and R > L in the anti-phase tasks.