Haya Akkad1, Flavio Di Stasio2, Robert Tibold1, Panagiotis Kassavetis3, John C Rothwell1, Mark J Edwards4. 1. Sobell Department of Motor Neuroscience & Movement Disorders, University College London Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK. 2. Neuromed Institute IRCCS, Via Atinense 18, 86077 Pozzilli, IS, Italy. 3. Sobell Department of Motor Neuroscience & Movement Disorders, University College London Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; Boston University, Neurology Department, Boston, MA, USA. 4. Sobell Department of Motor Neuroscience & Movement Disorders, University College London Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London WC1N 3BG, UK; Department of Cell Sciences, St George's University of London, Cranmer Terrace, London SW17, UK. Electronic address: medwards@sgul.ac.uk.
Abstract
OBJECTIVE: Surround inhibition (SI) is thought to facilitate focal contraction of a hand muscle by keeping nearby muscles silent. Unexpectedly, SI is reduced in skilled pianists. We tested whether repeated practice of focal contraction in non-pianists could reduce SI. METHODS: Motor-evoked potentials were elicited by transcranial magnetic stimulation in the relaxed abductor digiti minimi randomly at the onset and 5s after offset of a 2s focal contraction (10% maximum) of the first dorsal interosseous (FDI). Over 5 blocks of 40 trials participants obtained points for increasing contraction speed and stability in FDI. In a final block, the interval between contractions was varied randomly to increase attention to the task. RESULTS: Over the first 5 blocks, SI declined as performance (points scored) improved. In the final "attention" block SI increased towards baseline without affecting performance. CONCLUSIONS: Although SI may be useful during the early stages of learning, skilled focal finger movement does not require SI to prevent activity in non-involved muscles. This could be due to better targeting of the excitatory command to move. Results from the final block suggest that increased attention can re-engage SI when task parameters change. SIGNIFICANCE: SI is not necessary for successful focal contraction, but may contribute during learning and during attention to task.
OBJECTIVE: Surround inhibition (SI) is thought to facilitate focal contraction of a hand muscle by keeping nearby muscles silent. Unexpectedly, SI is reduced in skilled pianists. We tested whether repeated practice of focal contraction in non-pianists could reduce SI. METHODS: Motor-evoked potentials were elicited by transcranial magnetic stimulation in the relaxed abductor digiti minimi randomly at the onset and 5s after offset of a 2s focal contraction (10% maximum) of the first dorsal interosseous (FDI). Over 5 blocks of 40 trials participants obtained points for increasing contraction speed and stability in FDI. In a final block, the interval between contractions was varied randomly to increase attention to the task. RESULTS: Over the first 5 blocks, SI declined as performance (points scored) improved. In the final "attention" block SI increased towards baseline without affecting performance. CONCLUSIONS: Although SI may be useful during the early stages of learning, skilled focal finger movement does not require SI to prevent activity in non-involved muscles. This could be due to better targeting of the excitatory command to move. Results from the final block suggest that increased attention can re-engage SI when task parameters change. SIGNIFICANCE: SI is not necessary for successful focal contraction, but may contribute during learning and during attention to task.