Harnessing the Kohler Effect to Promote Motor Learning During Physically Assisted Rehabilitation

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PROJECT SUMMARY: Effective gait rehabilitation must be engaging, intense, repetitive, and focused on purposeful movement. However, patients after stroke can have neuromuscular or cognitive impairments that make this ideal unattainable without physical assistance. Paradoxically, this assistance can hinder motor recovery when patients habituate and reduce their sensorimotor engagement (the active correction of motor errors). To counter habituation and improve learning during assisted gait training, this project newly combines two theoretical frameworks: one from social psychology governing how social pressure impacts motivation, and another from neuroscience describing motor learning as processes of error-driven adaptation and reinforcement learning. Positive social pressure from working in a team can boost motivation compared to working individually, which may improve rehabilitation by enhancing active error correction and increasing the value of successful actions. This motivation enhancement in a team setting is termed the Köhler effect and is moderated by two mechanisms: upward social comparison (comparing self-performance to others) and indispensability (when success requires effort from all team members). Although these mechanisms have robust positive effects in exercise and cognitive tasks, their role in motor learning is unknown. Addressing this gap could improve rehabilitation care for millions who annually acquire and live with impairments from neurological injury. This fellowship’s complementary specific aims target the impact of each Köhler mechanism on locomotor rehabilitation. Aim 1 investigates how promoting upward social comparison affects sensorimotor engagement and motor learning during assisted locomotion and Aim 2 investigates the effects of indispensability. To enhance scientific rigor, a new model system is used: healthy participants walk on a treadmill and receive a standardized, temporary neuromotor impairment by electrically activating their right hamstrings during leg swing. This perturbation decreases participants’ net mechanical work during swing and shortens step length. The goal is to reach a target mechanical work while viewing step-by-step work feedback. Unlike a kinematic target, which a therapist can correct, the work goal can only be achieved if the participant contributes a significant amount of effort to the rehabilitation task. Showing the separated participant and therapist work contributions is expected to evoke upward social comparison. In Aim 2, therapist assistance is provided through a telerobotic system to rebalance effort contributions, making the therapist “weaker” and participants indispensable. This project is accompanied by a robust fellowship plan of interdisciplinary training that bridges neuroscience, rehabilitation, social psychology, engineering, and post-acute stroke care. The major theoretical advancement will be a new understanding of how sensorimotor engagement and motor learning are influenced by positive social pressure. The results will serve to increase the effectiveness of rehabilitation interventions by shifting patient perceptions, so they view themselves not as lesser contributors to a shared rehabilitation goal but as indispensable to success.