Tsujimoto T, Mima T, Shimazu H, Isomura Y
Directional organization of sensorimotor oscillatory activity related to the electromyogram in the monkey.
Clinical Neurophysiology 120 (2009) 1168-1173

In order to investigate cortical control of the electromyogram (EMG), we examined the directed transfer function (DTF) between the EMG and local field potential oscillations in the monkey sensorimotor area during both an isotonic muscle contraction task and the rest condition with EMG silence. DTF computation based on a multivariate model is suitable for analyzing the directional structure of a reciprocally interconnected system. We found that DTF between the cortex and EMG in the beta band is predominantly centrifugal and largest at the anterior bank of the central sulcus. As for the cortico-cortical DTF within the sensorimotor area, the effective connectivity in the beta band was reciprocal across the central sulcus but was dominated by a posterior-to-anterior

Figure 1

A: Schema of the asymmetric DTF in the beta band among 4 transcortical field potentials recorded from the monkey sensorimotor area and the EMG during the isotonic contraction of the brachioradialis muscle.

B: Schema of the asymmetric DTF in the beta band among 4 transcortical field potentials recorded from the monkey sensorimotor area during the rest condition with silent EMG of the brachioadialis muscle (baseline condition). Thickness of the arrow indicates the number of monkeys who showed significant asymmetry of DTF for the arrow direction.