Dissociable Roles for Working Memory in Sensorimotor Learning

Abstract

The computations underlying cognitive strategies in sensorimotor learning are poorly understood. Here we investigate such strategies in a sensorimotor transformation task. We show that strategies assume two forms, reflecting distinct working memory representations: discrete response caching of stimulus-response contingencies (e.g., look-up table; RC), and time-consuming parametric computations (e.g. mental rotation; MR). Subjects reaction times and errors suggest that both strategies are employed during learning, and trade off based on the progress of learning and the complexity of the task. Experiments using pressured preparation time support these working memory mechanisms: In discrete RC, time pressure elicits bimodal distributions of movements, in agreement with cached responses; in parametric MR, time pressure elicits a shifting distribution producing intermediate movements between visual targets and distal goals, consistent with analog re-computing of a movement plan. These results provide a specific model of working memory contributions to motor learning.