Visual Feedback Gain Affects Cognitive Motor Function During Constant Grip Strength Control: A Functional Near-Infrared Spectroscopy Study.

Visual feedback gain critically affects feedback quality and fine motor control, yet its neural basis related to cognitive motor control remains unclear. Nineteen healthy right-handed participants performed constant grip tracking at 20% of maximum voluntary contraction under low, medium, and high visual feedback gains. Functional near-infrared spectroscopy recorded hemodynamic responses from six regions of interest (ROIs): left/right prefrontal cortex (LPFC/RPFC), dorsolateral prefrontal cortex (DLPFC), left supplementary motor and premotor area (LSMA&PMA), left primary motor cortex (LM1), and left primary somatosensory cortex (LS1). Simultaneous grip force was collected. Under the medium gain level, the mean absolute error (MAE) was significantly lower than under both low ( ${P}\lt 0.001$ ) and high ( ${P}={0}.{036}$ ) gain levels. Compared to the low gain level, the medium gain level showed higher HbO peaks in the RPFC ( ${P}={0}.{022}$ ), DLPFC ( ${P}={0}.{011}$ ), LSMA&PMA ( ${P}={0}.{041}$ ) and LS1 ( ${P}={0}.{032}$ ), greater phase-locking value between ROIs within the LPFC-RPFC ( ${P}\lt 0.001$ ), RPFC-DLPFC ( ${P}={0}.{047}$ ) and DLPFC-LS1 ( ${P}={0}.{030}$ ), along with enhanced global coherence and higher clustering coefficients. Moreover, under the medium gain level, motor performance was significantly positively correlated with cortical activation across all six ROIs ( ${P}\lt 0.05$ ). These findings suggest medium visual feedback gain optimally balances spatial information, enabling efficient neural resource allocation and enhanced motor performance. This study offers novel insights into the neural mechanisms of visually guided precision grip.