Different forms of plasticity interact in adult humans

Neuroplasticity is maximal during development and declines in adulthood, especially for sensory cortices. On the other hand, the motor and prefrontal cortices retain plasticity throughout the lifespan. This difference has led to a modular view of plasticity in which different brain regions have their own plasticity mechanisms that do not depend or translate on others. Recent evidence shows that visual and motor plasticity share common neural mechanisms (e.g. GABAergic inhibition), indicating a possible link between these different forms of plasticity, however, the interaction between visual and motor plasticity has never been tested directly. Here we show that when visual and motor plasticity are elicited at the same time in adult humans, visual plasticity is impaired, while motor plasticity is spared. Moreover, simultaneous activation of working memory and visual plasticity also leads to impairment in visual plasticity. These unilateral interactions between visual, working memory and motor plasticity demonstrate a clear link between these three forms of plasticity. We conclude that local neuroplasticity in separate systems might be regulated globally, to preserve overall homeostasis in the brain. Here we investigated for the first time the interaction between visual plasticity, motor plasticity, and working memory in a group of adult human volunteers. We found a unilateral interaction between these forms of plasticity: when homeostatic visual plasticity is induced at the same time as motor plasticity or working memory, visual plasticity is disrupted. Our results indicate the existence of a global regulation mechanism in the brain linking different forms of plasticity. Understanding the link between different forms of plasticity is crucial for the development of new neuro-rehabilitative interventions on neurological diseases and brain injury.