Short-term limb immobilization affects cognitive motor processes

We examined the effects of a brief period of limb immobilization on the cognitive level of action control. A splint placed on the participants' left hand was used as a means of immobilization. We used a hand mental rotation task to investigate the immobilization-induced effects on motor imagery performance (Experiments 1 and 2) and a number mental rotation task to investigate whether immobilization-induced effects are also found when visual imagery is involved (Experiment 2). We also examined whether the effects of immobilization vary as a function of individuals' vividness of motor imagery (Experiment 2). The immobilized participants performed the mental rotation tasks before and immediately after the splint removal. The control group did not undergo the immobilization procedure. For hand stimuli, response time analysis showed a lack of task-repetition benefit following immobilization (Experiments 1 and 2) except when the visual imagery task was performed first (Experiment 2). Following immobilization, a flattening in the response time profile for left hand stimuli was observed as a function of stimuli rotation (Experiments 1 and 2), especially for participants with less vivid motor imagery (Experiment 2). We did not find an immobilization-induced effect on number stimuli. These findings revealed that the cognitive representation of hand movements is modified by immobilization and that sensorimotor deprivation specifically affects motor simulation of the immobilized hand. We discuss the possibility that immobilization affects the sensorimotor system due to the reduced processing of proprioceptive feedback, which lead some participants to switch from a motor to a visual imagery strategy.