Synchronization in Monkey Motor Cortex During a Precision Grip Task. II. Effect of Oscillatory Activity on Corticospinal Output

Abstract

Baker, Stuart N., Elizabeth M. Pinches, and Roger N. Lemon. Synchronization in monkey motor cortex during a precision grip task. II. Effect of oscillatory activity on corticospinal output. J Neurophysiol 89: 1941Neurophysiol 89: -1953Neurophysiol 89: , 2003 10.1152/jn.00832.2002. Recordings from primary motor cortex (M1) during periods of steady contraction show oscillatory activity; these oscillations are coherent with the activity of contralateral muscles. We investigated synchronization of corticospinal output neurons with the oscillations, which could provide the pathway for their transmission to the spinal motoneurons. One hundred seventy-six antidromically identified pyramidal tract neurons (PTNs) were recorded from M1 in three macaque monkeys trained to perform a precision grip task. Local field potentials (LFP) were simultaneously recorded. All analysis was confined to the hold period of the task, where our previous work has shown that there is the strongest oscillatory activity. Coherence was calculated between LFP and PTN discharge. Significant coherence was seen in three bands, with frequencies of 10 -14, 17-31, and 34 -44 Hz. Coherence values were low, with the majority of PTN-LFP coherences having a peak lower than 0.05. The phase of coherence was approximately Ϫ/2 radians for each band (with LFP polarity defined as negative upward), although there was some dispersion of phase across the population of PTNs. Coherence was also calculated between pairs of PTNs that had been simultaneously recorded. Where there was significant coherence, it was also generally smaller than 0.05. The phase of PTN-PTN coherence clustered around zero radians. A computer model was constructed to assist the interpretation of the experimental results. It simulated an integrate-and-fire neuron responding to synaptic inputs. A fraction of the synaptic inputs was synchronized with a simulated LFP; the remainder were uncorrelated with it. The model showed that coherence between the LFP and the output spike train considerably underestimated the fraction of synchronized inputs. Additionally, for a given fraction of synchronized inputs, coherence was smaller for high-compared with low-frequency bins. Cell discharge rate also influenced the spike-LFP coherence: coherence was higher for simulations in which the cell discharged at a faster rate. Thus although levels of PTN-LFP coherence seen experimentally were low, a considerable proportion of the input to the PTN must be synchronized with the global oscillatory activity recorded by the LFP. The low LFP-PTN coherences do however indicate that cortical oscillations are transmitted with only low fidelity in the discharge of a single PTN. Using further computer simulations, it was demonstrated that a small population of PTNs could encode the cortical oscillatory signal effectively, since the action of averaging across the population improves the signal:noise ratio. The oscillations will therefore be effectively transmitted to spinal motoneurons, and this has important consequences for ...

The reorganization of corticomuscular coherence during a transition between sensorimotor states

“…Evidence from the past two decades of research suggests that neural oscillations subserve important cognitive functions, including motor control (Fries, 2005;Schnitzler and Gross, 2005;Fetz, 2013). During sustained contractions, primary motor cortex shows oscillations in alpha (8 12 Hz) and beta (15 30 Hz) bands (Murthy and Fetz, 1992;Sanes and Donoghue, 1993;Baker et al, 2003). Although oscillations in both frequency bands are e↵ectively carried down the corticospinal tract (Baker et al, 2003), most studies using sustained contractions find that only beta-band oscillations are coherent between motor cortex and muscle activity Halliday et al, 1998;Baker et al, 1997;Gross et al, 2000).…”

“…During sustained contractions, primary motor cortex shows oscillations in alpha (8 12 Hz) and beta (15 30 Hz) bands (Murthy and Fetz, 1992;Sanes and Donoghue, 1993;Baker et al, 2003). Although oscillations in both frequency bands are e↵ectively carried down the corticospinal tract (Baker et al, 2003), most studies using sustained contractions find that only beta-band oscillations are coherent between motor cortex and muscle activity Halliday et al, 1998;Baker et al, 1997;Gross et al, 2000). Corticomuscular beta-band coherence is most prominent during tonic muscle contractions and disappears during movement (Baker et al, 1997;Riddle and Baker, 2006;Kilner et al, 2000;Baker et al, 1999) and beta-band activity is enhanced when higher precision is required Kristeva-Feige et al, 2002;Witte et al, 2007;Gilbertson et al, 2005).…”

Behavioral Context and Coherent Oscillations in the Supplementary Motor Area

“…On the one hand, it has been proposed that spikes of multiple neurons are synchronized when individual features coded by such neurons belong to a common object (Gray, 1999;Singer, 1999;von der Malsburg, 1999). Similarly, synchronous spikes in the motor cortical areas have been proposed as a means to bind individual movement segments to produce complex movement patterns (Pfurtscheller et al, 1993;Murthy and Fetz, 1996a,b;MacKay, 1997;Riehle et al, 1997;Donoghue et al, 1998;Lebedev and Wise, 2000;Ohara et al, 2001;Baker et al, 2003). Experimental support for this hypothesis, unfortunately, has not been consistent (Lamme and Spekreijse, 1998;Thiele and Stoner, 2003).…”

Medidas eletrencefalográficas durante a aprendizagem de tarefa motora sob efeito do bromazepam

“…Part i c u l a rmente questões motoras envolvendo aprendizagem têm sido investigadas através de várias metodologias 1 3 . Medidas eletrencefalográficas EEG vêm sendo utilizadas a fim de se analisar processos motores relacionados à aprendizagem 14 , bem como para avaliar alterações eletrocorticais decorrentes da administração de drogas com efeito sobre o sistema nervoso central (SNC) 15 . Este estudo tem por objetivo: (1) analisar as alterações motoras e eletrocorticais decorrentes da administração de diferentes doses de benzodiazepínico (bromazepam) mediante a prática de tare f a motora; e (2) relacionar o efeito da droga a perf o rmance motora mão-dominante versus não dominante.…”