Do prism and other adaptation paradigms really measure the same processes?

Sensorimotor plasticity allows the nervous system to set up appropriate motor and sensory compensations when individuals face changing demands in a given motor task. A much-debated question in neuroscience research is the identification of processes that encompass this capacity of plasticity. Prism adaptation is the oldest experimental paradigm that has been used to achieve this goal (Helmholtz, 1867). Since 1990's, other paradigms have emerged such as visuomotor rotations or dynamical perturbations (inertial Coriolis forces, velocity-dependent force-field). We compared these paradigms with respect to three specific methodological features: application of the perturbation, after-effects, and generalization. This work aimed to shed light on the following central issue: Do all these paradigms involve similar processes? We used generalization properties-a relevant feature associated with the credit assignment problem-to emphasize the involvement of different processes in "adaptation" paradigms. We therefore classified these processes based on the context specificity of elicited transformations. This review reveals that the processes involved are closely linked to paradigm-related experimental conditions. Context-independent processes appear to be favored when errors are attributed to our own sensorimotor performance (prism, Coriolis) whereas context-dependent processes appear to be mostly mediated by attribution of errors to a specific external interface (visuomotor rotation, force-field). This work encourages researchers to consider the methodological aspects specific to each paradigm for future investigations of sensorimotor plasticity.

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