Workshop 3: Changes in neural orchestration and the neural code W3-1: Neural synchrony during bimanual motor behaviour and visuotactile integration

Christian Gerloff University Medical Center Hamburg-Eppendorf, Department of Neurology Converging evidence indicates that information can be represented in the brain by the functional coupling of distant brain areas. Here, 3 sets of experiments addressing interregional neural synchrony in humans during integrative sensorimotor behaviour are reviewed. The conclusion of a first study (Andres et al. 1999) was that task-related coherence (TRCoh) reflects changes in interhemispheric communication that are specifically related to bimanual learning and may be relayed through the corpus callosum. Further analyses with partial task-related coherence and directed transfer function as well as with fMRI pointed to a crucial role of the posterior parietal cortex as a region acting as a driver of bimanual motor integration. The conclusion of a second set of experiments (Hummel and Gerloff 2005) was that the amount of long-range synchrony is quantitatively linked with the degree of behavioural success in humans in a visuo-tactile integration paradigm. The ability to generate topographically specific synchrony of high amplitude appeared to be functionally relevant for behavioural success. In this study, the divergence between (unchanged) local activation and (dynamically modulated) TRCoh raised the possibility that magnitude of regional activation is less representative of the efficacy of brain functioning than interregional synchrony. The conclusion of a third set of experiments (Plewnia et al. 2008) was that synchronous bifocal transcranial magnetic stimulation (TMS) is feasible for selective modulation of interregional EEG coherence. In summary, (i) EEG coherence shows specific modulations during tasks requiring large-scale neuronal interaction, (ii) variations of interregional neural synchrony are quantitatively linked to the level of behavioural performance, and (iii) it is possible to modulate interregional synchrony with bifocal TMS, rendering it possible in the future to address the functional causal relationship between connectivity measures and behaviour more directly.