Adaptation of surround inhibition in the human motor system

• Published in: Experimental brain research Vol. 222; no. 3; pp. 211 - 217
• Main Authors: Kassavetis, P., Saifee, T. A., Sadnicka, A., Pareés, I., Kojovic, M., Rothwell, J. C., Edwards, M. J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.10.2012; Springer; Springer Nature B.V
• Subjects: Adaptation; Adaptation, Physiological - physiology; Adaptations; Analysis of Variance; Biofeedback, Psychology - physiology; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Cortex (motor); Electromyography; EMG; Evoked Potentials, Motor - physiology; Eye and associated structures. Visual pathways and centers. Vision; Feedback; Female; Finger; Fundamental and applied biological sciences. Psychology; Humans; Male; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor systems; Movement - physiology; Muscle, Skeletal - physiology; Muscles; Neural Inhibition - physiology; Neurology; Neurosciences; Reaction Time; Research Article; Time Factors; Transcranial Magnetic Stimulation; Vertebrates: nervous system and sense organs; Vibration; Visual perception; United Kingdom > UK; Muscle vibration; Transcranial magnetic stimulation; Surround inhibition; Human; Vibration; Motor pathway; Response amplitude; Central nervous system; Electrophysiology; Abductor digiti minimi muscle; Encephalon; Motor cortex; Magnetic stimulus; Electromyography; Timing; Abductor muscle
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-012-3207-4

Adaptation of a rapid ballistic movement requires that commands for the next movement are updated on the basis of sensory error signals from the current movement. Previous experiments, mostly using visual feedback, have demonstrated that adaptation is highly sensitive to the timing of feedback and can be substantially impaired by delays of 100 ms or so. Here, we use the phenomenon of surround inhibition (SI) to explore the consequences of somatosensory feedback delay in a task requiring participants to flex the index finger without generating any electromyographical (EMG) activity in other fingers. Participants were requested to perform brief isolated flexion movements of the index finger. After a short period of practice, SI in the distant abductor digiti minimi (ADM) muscle was quantified by measuring the amplitude of EMG responses evoked by a standard pulse of transcranial magnetic stimulation to the contralateral motor cortex at the onset of flexion. SI indicates that the response during flexion was smaller than the response at rest. After this, two training blocks were performed in which the ADM muscle was vibrated (80 Hz, 100 ms) either at the onset (VIB onset ) of finger flexion or with a delay of 100 ms (VIB 100 ). SI was reassessed after training. SI measured after VIB onset training was transiently more effective than at baseline. In contrast, SI was unchanged compared to baseline after VIB 100 . The present study demonstrates that SI can be modified by experience. The timing of the sensory stimulation was found to be critical for the modification of SI, suggesting that only sensory signals closely related to the movement onset can induce adaptive changes, presumably through a feed-forward process.