Author(s): KUHN, Y., PILLONEL, M., RUFFIEUX, J., LAUBER, B., TAUBE, W., Institution: UNIVERSITY OF FRIBOURG, Country: SWITZERLAND, Abstract-ID: 1598

INTRODUCTION:
Motor surround inhibition (SI) is a neurophysiological mechanism that suppresses the excitability of surrounding muscles during voluntary movement and contributes to skilled motor control [1]. Previous studies indicate that an external focus of attention (EF), compared to an internal one (IF), induces distinct neurophysiological processes [2], including enhanced motor SI [3]. In parallel, augmented feedback (AF) is known to enhance motor performance [4]; however, its effects on underlying neurophysiological mechanisms, such as SI, and its interaction with attentional focus remain unclear. The aim of the present study was to investigate the effects of adopting an IF, EF, AF, or their combination (AF+EF) on motor performance and, most importantly on motor SI in the primary motor cortex (M1).
METHODS:
Young healthy participants (n = 15, 20-25 y) performed a rate of force development (RFD) task with the right index finger by pressing on a force plate following an auditory cue. Four experimental conditions were tested: IF, EF, AF, and AF+EF. While performing the motor task, single-pulse transcranial magnetic stimulation (TMS) was delivered over the M1, either at rest or just before movement onset. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseous (FDI, prime mover) and the abductor pollicis brevis (APB, surrounding muscle).
RESULTS:
At the behavioral level, RFD was significantly enhanced (i.e. the steepest slope of the force-time curve) in the AF condition compared to EF and IF, with EF also outperforming IF (all p < 0.02). However, combining AF+EF did not further improve performance. At the neurophysiological level, MEPs recorded from the surrounding muscle (APB) showed the greatest SI in the AF condition, followed by EF and IF, indicating progressively stronger SI across conditions (all p < 0.05). Again, no additional increase in SI was observed in the AF+EF condition. MEP amplitudes at rest in the prime mover (FDI) did not differ across conditions, and no significant differences were found in background electromyographic activity.
CONCLUSION:
These results confirm that adopting an EF induces stronger motor SI than an IF, in line with previous findings [2, 3]. Most importantly, the present study demonstrates that AF induces immediate changes in neural control strategies, resulting in increased SI and improved motor performance. Overall, this study provides new evidence that performance gains induced by AF are at least partly mediated by enhanced SI within M1. Importantly, these findings identify AF as a novel and potent modulator of motor SI. Although no additional effect was observed when combining AF and EF, it remains unclear whether this reflects a ceiling effect.
References
1. Beck et al. (2008). J Neurosci
2. Kuhn & Taube (2025). Exerc Sport Sci Rep
3. Kuhn et al. (2018). Sci Rep
4. Petancevski et al. (2022). Psychol Sport Ex