Effect of prior somatosensory electrical stimulation on the wrist in biasing human hand choice

Hand choice is an unconscious decision frequently made in daily life. A correlation has been found between the state of brain activity before target presentation and hand choice for the target, around which the hand choice probability is in equilibrium. However, whether the neural state before target presentation affects hand choice remains unknown. Therefore, this study aimed to examine whether instantaneous somatosensory electrical stimulation administered to the unilateral wrist at 0, 300, or 600 ms before the target presentation facilitates or inhibits stimulated hand choice for targets around the hand selection equilibrium point. A single electrical stimulation comprised five trains of 1 ms electrical pulses, with a 20 ms inter-pulse interval. The stimulus intensity was set at 80% of the motor threshold. Fourteen right- handed healthy adults (five females, nine males; mean age, 25.1 {+/-} 4.64 years) participated. Unilateral wrist stimulation significantly increased the probability of choosing the stimulated hand and led to a faster reaction time than bilateral wrist stimulation and no-stimulation conditions. The results suggest that prior somatosensory stimulation significantly affects the hand-choice process, effectively promoting selection of the stimulated hand. These findings highlight the potential application of this stimulation method in stroke rehabilitation to facilitate use of the paretic hand. Impact StatementPrior neural stimulation significantly affected the hand-selection process by promoting the selection of the stimulated hand, thus potentially beneficial in rehabilitating the paretic hand of patients with stroke.