Phase reorganization leads to transient β-LFP spatial wave patterns in motor cortex during steady-state movement preparation

Michael Rule, Carlos E. Vargas-Irwin, John P. Donoghue, Wilson Truccolo

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Abstract / Description of output

Previous studies on the origin and properties of spatial patterns in motor cortex beta local field potential (β-LFP) oscillations have focused on planar traveling waves. However, it is unclear (a) whether β-LFP waves are limited to plane waves, or even (b) whether they are propagating waves of excito-excitatory activity, i.e. primarily traveling waves in excitable media; they could reflect, instead, reorganization in the relative phases of transient oscillations at different spatial sites. We addressed these two problems in β-LFPs recorded via microelectrode arrays implanted in three adjacent motor-cortex areas of non-human primates during steady-state movement preparation. Our findings are fourfold: (1) β-LFP wave patterns emerged as transient events, despite stable firing rates of single neurons concurrently recorded during the same periods. (2) β-LFP waves showed a richer variety of spatial dynamics, including rotating and complex waves. (3) β-LFP wave patterns showed no characteristic wavelength, presenting instead a range of scales with global zero-lag phase synchrony as a limiting case - features surprising for purely excito-excitatory waves, but consistent with waves in coupled oscillator systems. (4) Furthermore, excito-excitatory traveling waves induced by optogenetic stimulation in motor cortex showed, in contrast, a characteristic wavelength and reduced phase synchrony. Overall, β-LFP wave statistics differed from those of induced traveling waves in excitable media recorded under the same microelectrode-array setup. Our findings suggest phase reorganization in neural coupled-oscillators contribute significantly to the origin of transient β-LFP spatial dynamics during preparatory steady-states, and outline important constraints for spatially-extended models of β-LFP dynamics in motor cortex.
Original languageEnglish
Number of pages37
JournalJournal of Neurophysiology
Early online date14 Feb 2018
DOIs
Publication statusE-pub ahead of print - 14 Feb 2018

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