Citation: Journal of Neurophysiology. 117(2):655-664, 2017 Feb 01.Journal: Journal of neurophysiology.Published: 2017ISSN: 0022-3077.Full author list: Nguyen HB; Lee SW; Harris-Love ML; Lum PS.UI/PMID: 27852730.Subject(s): Adult | Analysis of Variance | Elbow/ph [Physiology] | Electromyography | *Feedback, Sensory/ph [Physiology] | Female | Functional Laterality/ph [Physiology] | Humans | *Isometric Contraction/ph [Physiology] | Male | *Muscle, Skeletal/ph [Physiology] | *Psychomotor Performance/ph [Physiology] | Reflex/ph [Physiology] | Young AdultInstitution(s): MedStar National Rehabilitation NetworkActivity type: Journal Article.Medline article type(s): Journal ArticleDigital Object Identifier: https://dx.doi.org/10.1152/jn.00269.2016 (Click here)Abbreviated citation: J Neurophysiol. 117(2):655-664, 2017 Feb 01.Local Holdings: Available online from MWHC library: 1997 - present (after 1 year).Abstract: While the effects of sensory feedback on bimanual tasks have been studied extensively at two ends of the motor control hierarchy, the cortical and behavioral levels, much less is known about how it affects the intermediate levels, including neural control of homologous muscle groups. We investigated the effects of somatosensory input on the neural coupling between homologous arm muscles during bimanual tasks. Twelve subjects performed symmetric elbow flexion/extension tasks under different types of sensory feedback. The first two types involve visual feedback, with one imposing stricter force symmetry than the other. The third incorporated somatosensory feedback via a balancing apparatus that forced the two limbs to produce equal force levels. Although the force error did not differ between feedback conditions, the somatosensory feedback significantly increased temporal coupling of bilateral force production, indicated by a high correlation between left/right force profiles (P < 0.001). More importantly, intermuscular coherence between biceps brachii muscles was significantly higher with somatosensory feedback than others (P = 0.001). Coherence values also significantly differed between tasks (flexion/extension). Notably, whereas feedback type mainly modulated coherence in the alpha- and gamma-bands, task type only affected beta-band coherence. Similar feedback effects were observed for triceps brachii muscles, but there was also a strong phase effect on the coherence values (P < 0.001) that could have diluted feedback effects. These results suggest that somatosensory feedback can significantly increase neural coupling between homologous muscles. Additionally, the between-task difference in beta-band coherence may reflect different neural control strategies for the elbow flexor and extensor muscles.Abstract: NEW & NOTEWORTHY: This study investigated the effects of somatosensory feedback during bimanual tasks on the neural coupling between arm muscles, which remains largely unexplored. Somatosensory feedback using a balancing apparatus, compared with visual feedback, significantly increased neural coupling between homologous muscles (indicated by intermuscular coherence values) and improved temporal correlation of bilateral force production. Notably, feedback type modulated coherence in the alpha- and gamma-bands (more subcortical pathways), whereas task type mainly affected beta-band coherence (corticospinal pathway).Abstract: Copyright � 2017 the American Physiological Society.