We continuously adapt our movements in daily life, forming new internal models whenever necessary and updating existing ones. Recent work has suggested that this flexibility is enabled via sensorimotor cues, serving to access the correct internal model whenever necessary and keeping new models apart from previous ones. While research to date has mainly focused on identifying the nature of such cue representations, here we investigated whether and how these cue representations generalize, interfere, and transfer within and across effector systems. Subjects were trained to make two-stage reaching movements: a pre-movement that served as a cue, followed by a targeted movement that was perturbed by one of two opposite curl force fields. The direction of the pre-movement was uniquely coupled to the direction of the ensuing force field, enabling simultaneous learning of the two respective internal models. After training, generalization of the two pre-movement cues' representations was tested at untrained pre-movement directions, both within the trained and untrained hand. We show that the individual pre-movement representations generalize in a Gaussian like pattern around the trained pre-movement direction. When the force fields are of unequal strengths, the cue-dependent generalization skews toward the strongest field. Furthermore, generalization patterns transfer to the non-trained hand, in an extrinsic reference frame. We conclude that contextual cues do not serve as discrete switches between multiple internal models. Instead, their generalization suggests a weighted contribution of the associated internal models based on the angular separation from the trained cues to the net motor output.
- motor adaptation
- contextual cues
- interlimb transfer
- Copyright © 2015, Journal of Neurophysiology