Existing Motor State Is Favored at the Expense of New Movement during 13-35 Hz Oscillatory Synchrony in the Human Corticospinal System

Abstract

Oscillations in local field potentials in the ␤-frequency band (13-35 Hz) are a pervasive feature of human and nonhuman primate motor cortical areas. However, the function of such synchronous activity across populations of neurons remains unknown. Here, we test the hypothesis that ␤ activity may promote existing motor set and posture while compromising processing related to new movements. Three experiments were performed. First, healthy subjects were instructed to make reaction time movements of the outstretched index finger in response to imperative cues triggered by transient increases in corticospinal synchrony, as evidenced by phasic elevations of ␤-frequency band microtremor and intermuscular synchrony. Second, healthy subjects were instructed to resist a stretch to the index finger triggered in the same way. Finger acceleration in the reaction time task and transcortical components of the stretch reflex were measured and compared with those elicited by random cue or stretch presentation. Finally, we sought a correlation between finger acceleration in the reaction time task and cortical synchrony directly measured from the electrocorticogram in two patients undergoing functional neurosurgery. We demonstrate that movements are slowed and transcortical responses to stretch are potentiated during periods of elevated ␤-band cortical synchrony. The results suggest that physiological periods of ␤ synchrony are associated with a cortical state in which postural set is reinforced, but the speed of new movements impaired. The findings are of relevance to Parkinson's disease, in which subcortical and cortical ␤-band synchronization is exaggerated in the setting of increased tone and slowed movements.

Being an agent or an observer: Different spectral dynamics revealed by MEG

“…Notably, the beta oscillations appear to be at a frequency which is 508 twice the alpha components, thus producing the arch--shaped µ rhythm. This is in line with a 509 concomitant modulation of the alpha and beta bands recorded over somato--sensory regions 510 by (Baker, 2007;Gilbertson et al, 2005), proposed that beta band oscillations is not purely an 519 "idling" rhythm, but bolster an active process that promotes the ongoing motor set and other 520 processes beyond the domain of motor control. 521…”

Dynamic Neural Correlates of Motor Error Monitoring and Adaptation during Trial-to-Trial Learning

“…However, there is evidence that allows us to consider the distinction still further. Given that the cerebellum is thought to play a preeminent role in the updating of internal models (Maschke et al, 2004;Smith and Shadmehr, 2005), whereas the primary motor cortex plays a more important role in retention in motor adaptation (Hadipour-Niktarash et al, 2007;Galea et al, 2011), a reasonable supposition is that the postmovement ␤ ERS is related to the activity of cortical inputs from the cerebellar receiving nuclei of the thalamus. Consistent with this, studies in patients with thalamic lesions suggest that the motor thalamus facilitates cortical ␤ oscillations (Van Der Werf et al, 2006), and those with direct recordings from thalamus demonstrate ␤-band coherence between sensorimotor cortex and motor thalamus that is attenuated in subjects with suspected cerebellar pathology (Marsden et al, 2000).…”

“…But why should related motor cortical activity be focused in the ␤ frequency band? One current theory seeking to explain the function of ␤ activity is that it promotes the status quo (Gilbertson et al, 2005;Engel and Fries, 2010), or, in the present context, acts to preserve the set of motor commands that achieved the last response. Motor areas of the basal ganglia might also be involved in this function, given the ␤-band coherence between activities in these nuclei and sensorimotor cortex increases after movement (Litvak et al, 2012) and the recent observation that ␤ power in ventral striatum increases after goal-reaching on correct trials and with learning in rodents (Howe et al, 2011).The heightened ␤ synchronization after responses with minimal angular error might then reinforce the motor commands or forward model that requires little updating.…”

Internalized Timing of Isochronous Sounds Is Represented in Neuromagnetic Beta Oscillations

“…The functional difference between beta suppression and rebound found here is in line with the literature. It is widely accepted that beta desynchronization indicates an "active change" in the status of sensorimotor processing (Pfurtscheller and Lopes da Silva, 1999), whereas the beta increase is associated with "maintaining an existing steady state in motor control" (Gilbertson et al, 2005;Pogosyan et al, 2009), "immobilization" (Salmelin et al, 1995), or "reset of an existing cortical network" (Pfurtscheller et al, 2005), reflecting a variety of task and attentional demands. For sensorimotor tasks, slightly different cortical areas seem to be involved in beta suppression and rebound (Salmelin and Hari, 1994;Salmelin et al, 1995;Jurkiewicz et al, 2006;Caetano et al, 2007;Bardouille et al, 2010).…”