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Corticomuscular coherence between motor cortex, somatosensory areas and forearm muscles in the monkey.

Witham CL, Wang M, Baker SN - Front Syst Neurosci (2010)

Bottom Line: Significant beta-band ( approximately 20 Hz) corticomuscular coherence was found in all areas investigated.Directed coherence (Granger causality) analysis was used to investigate the direction of effects.Directed coherence showed large beta-band effects from S1/PPC to M1, with smaller directed coherence in the reverse direction.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne Tyne and Wear, UK.

ABSTRACT
Corticomuscular coherence has previously been reported between primary motor cortex (M1) and contralateral muscles. We examined whether such coherence could also be seen from somatosensory areas. Local field potentials (LFPs) were recorded from primary somatosensory cortex (S1; areas 3a and 2) and posterior parietal cortex (PPC; area 5) simultaneously with M1 LFP and forearm EMG activity in two monkeys during an index finger flexion task. Significant beta-band ( approximately 20 Hz) corticomuscular coherence was found in all areas investigated. Directed coherence (Granger causality) analysis was used to investigate the direction of effects. Surprisingly, the strongest beta-band directed coherence was in the direction from S1/PPC to muscle; it was much weaker in the ascending direction. Examination of the phase of directed coherence provided estimates of the time delay from cortex to muscle. Delays were longer from M1 ( approximately 62 ms for the first dorsal interosseous muscle) than from S1/PPC ( approximately 36 ms). We then looked at coherence and directed coherence between M1 and S1 for clues to this discrepancy. Directed coherence showed large beta-band effects from S1/PPC to M1, with smaller directed coherence in the reverse direction. The directed coherence phase suggested a delay of approximately 40 ms from M1 to S1. Corticomuscular coherence from S1/PPC could involve multiple pathways; the most important is probably common input from M1 to S1/PPC and muscles. If correct, this implies that somatosensory cortex receives oscillatory efference copy information from M1 about the motor command. This could allow sensory inflow to be interpreted in the light of its motor context.

No MeSH data available.


Schematic showing possible pathways underlying coherence between S1/area 5 and EMG. Lettered labels are referred to in text.
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Figure 7: Schematic showing possible pathways underlying coherence between S1/area 5 and EMG. Lettered labels are referred to in text.

Mentions: Several pathways could provide the substrate for descending corticomuscular coherence from S1. Figure 7 shows four schematics of possible pathways using the main known connections between M1, S1 and the periphery. One possibility is that M1 and S1 activity is synchronized by common input from another region (Figure 7, Pathway 1); this is a reasonable option, as – for example – both SMA (Darian-Smith et al., 1993) and SII (Jones, 1986) are known to provide input to primary motor and somatosensory cortices. However, given the close spatial proximity of the pre- and post-central regions which we investigated, we would expect that conduction delays from the distant area to each would be similar. If synchronization with muscle was then mediated via fast corticospinal axons from M1, this would lead to similar delay estimates from all of the studied cortical areas to muscle. In fact, the delays differed between parietal and motor cortex.


Corticomuscular coherence between motor cortex, somatosensory areas and forearm muscles in the monkey.

Witham CL, Wang M, Baker SN - Front Syst Neurosci (2010)

Schematic showing possible pathways underlying coherence between S1/area 5 and EMG. Lettered labels are referred to in text.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2927302&req=5

Figure 7: Schematic showing possible pathways underlying coherence between S1/area 5 and EMG. Lettered labels are referred to in text.
Mentions: Several pathways could provide the substrate for descending corticomuscular coherence from S1. Figure 7 shows four schematics of possible pathways using the main known connections between M1, S1 and the periphery. One possibility is that M1 and S1 activity is synchronized by common input from another region (Figure 7, Pathway 1); this is a reasonable option, as – for example – both SMA (Darian-Smith et al., 1993) and SII (Jones, 1986) are known to provide input to primary motor and somatosensory cortices. However, given the close spatial proximity of the pre- and post-central regions which we investigated, we would expect that conduction delays from the distant area to each would be similar. If synchronization with muscle was then mediated via fast corticospinal axons from M1, this would lead to similar delay estimates from all of the studied cortical areas to muscle. In fact, the delays differed between parietal and motor cortex.

Bottom Line: Significant beta-band ( approximately 20 Hz) corticomuscular coherence was found in all areas investigated.Directed coherence (Granger causality) analysis was used to investigate the direction of effects.Directed coherence showed large beta-band effects from S1/PPC to M1, with smaller directed coherence in the reverse direction.

View Article: PubMed Central - PubMed

Affiliation: Institute of Neuroscience, Newcastle University, Newcastle upon Tyne Tyne and Wear, UK.

ABSTRACT
Corticomuscular coherence has previously been reported between primary motor cortex (M1) and contralateral muscles. We examined whether such coherence could also be seen from somatosensory areas. Local field potentials (LFPs) were recorded from primary somatosensory cortex (S1; areas 3a and 2) and posterior parietal cortex (PPC; area 5) simultaneously with M1 LFP and forearm EMG activity in two monkeys during an index finger flexion task. Significant beta-band ( approximately 20 Hz) corticomuscular coherence was found in all areas investigated. Directed coherence (Granger causality) analysis was used to investigate the direction of effects. Surprisingly, the strongest beta-band directed coherence was in the direction from S1/PPC to muscle; it was much weaker in the ascending direction. Examination of the phase of directed coherence provided estimates of the time delay from cortex to muscle. Delays were longer from M1 ( approximately 62 ms for the first dorsal interosseous muscle) than from S1/PPC ( approximately 36 ms). We then looked at coherence and directed coherence between M1 and S1 for clues to this discrepancy. Directed coherence showed large beta-band effects from S1/PPC to M1, with smaller directed coherence in the reverse direction. The directed coherence phase suggested a delay of approximately 40 ms from M1 to S1. Corticomuscular coherence from S1/PPC could involve multiple pathways; the most important is probably common input from M1 to S1/PPC and muscles. If correct, this implies that somatosensory cortex receives oscillatory efference copy information from M1 about the motor command. This could allow sensory inflow to be interpreted in the light of its motor context.

No MeSH data available.