Beta oscillations in a large-scale sensorimotor cortical network: Directional influences revealed by Granger causality

TLDR

Synchronized beta oscillations (14‑30 Hz) in primary motor cortex help maintain steady contralateral arm and hand contractions, but the role of postcentral areas and their interactions with motor cortex remain poorly understood. The study examined how beta‑synchronized neuronal assemblies in pre‑ and postcentral cortex interact while monkeys performed a lever‑press task during a visual discrimination wait period. Power and coherence spectral analysis revealed a large‑scale beta‑synchronized network between pre‑ and postcentral areas, and Granger causality spectra quantified directional influences among recording sites. Strong Granger causal influences flowed from primary somatosensory cortex to motor cortex and inferior posterior parietal cortex, with the latter also influencing motor cortex; motor‑to‑postcentral influences were weak or absent, showing that synchronized beta oscillations link multiple sensorimotor areas into a large‑scale network during motor maintenance.

Abstract

Previous studies have shown that synchronized beta frequency (14-30 Hz) oscillations in the primary motor cortex are involved in maintaining steady contractions of contralateral arm and hand muscles. However, little is known about the role of postcentral cortical areas in motor maintenance and their patterns of interaction with motor cortex. We investigated the functional relations of beta-synchronized neuronal assemblies in pre- and postcentral areas of two monkeys as they pressed a hand lever during the wait period of a visual discrimination task. By using power and coherence spectral analysis, we identified a beta-synchronized large-scale network linking pre- and postcentral areas. We then used Granger causality spectra to measure directional influences among recording sites. In both monkeys, strong Granger causal influences were observed from primary somatosensory cortex to both motor cortex and inferior posterior parietal cortex, with the latter area also exerting Granger causal influences on motor cortex. Granger causal influences from motor cortex to postcentral sites, however, were weak in one monkey and not observed in the other. These results are the first, to our knowledge, to demonstrate in awake monkeys that synchronized beta oscillations bind multiple sensorimotor areas into a large-scale network during motor maintenance behavior and carry Granger causal influences from primary somatosensory and inferior posterior parietal cortices to motor cortex.