Neurophysiological assessment of manual dexterity in healthy subjects

Objective: Manual dexterity refers to skill in using the hands and fingers to perform fine movements. This study aimed to validate the kinematic assessment of Coin Rotation Task (CRT) as an objective measure of manual dexterity and to investigate its neurophysiological correlates. Methods: Thirty healthy young adults underwent CRT kinematic recording and analysis. Test–retest reliability was assessed in a subgroup of fifteen participants. This same subgroup also underwent finger tapping (FT) kinematic recordings to enable comparisons across motor tasks. Additionally, transcranial magnetic stimulation (TMS) was applied to evaluate corticospinal excitability and interhemispheric inhibition (IHI). Asymmetry indices were calculated for both the kinematic and TMS data. Results: Kinematic analysis of CRT revealed a higher number of rotations, greater peak velocities, and smoother movement trajectories in the dominant hand, with moderate-to-good test–retest reliability for these measures. Moreover, CRT kinematics showed clear sensitivity to hand dominance, whereas FT kinematics did not demonstrate significant lateralization. While raw TMS measures were not related to performance, asymmetry in interhemispheric inhibition (IHI) was significantly correlated with CRT velocity asymmetry, suggesting a link between inhibitory balance and manual dexterity performance. Conclusions: The kinematic analysis of CRT represents a sensitive and selective tool for objectively characterizing manual dexterity. Behavioral asymmetries reflect imbalance of interhemispheric inhibitory influences. Significance: This study provides an integrated neurophysiological analysis of manual dexterity in healthy subjects and discloses its relationship with interhemispheric organization. The proposed methodology holds potential for applications in the study of motor disorders.