Adaptation to proprioceptive targets following visuomotor adaptation.

In the following study, we asked if reaches to proprioceptive targets are updated following reach training with a gradually introduced visuomotor perturbation. Subjects trained to reach with distorted hand-cursor feedback, such that they saw a cursor that was rotated or translated relative to their actual hand movement. Following reach training trials with the cursor, subjects reached to Visual (V), Proprioceptive (P) and Visual + Proprioceptive (VP) targets with no visual feedback of their hand. Comparison of reach endpoints revealed that reaches to VP targets followed similar trends as reaches to P targets, regardless of the training distortion introduced. After reaching with a rotated cursor, subjects adapted their reaches to all target types in a similar manner. However, after reaching with a translated cursor, subjects adapted their reach to V targets only. Taken together, these results show that following training with a visuomotor distortion, subjects primarily rely on proprioceptive information when reaching to VP targets. Furthermore, results indicate that reach adaptation to P targets depends on the distortion presented. Training with a rotation distortion leads to changes in reaches to both V and P targets, while a translation distortion, which introduces a constant discrepancy between visual and proprioceptive estimates of hand position throughout the reach, affects changes to V but not P targets.

The rapid-chase theory does not extend to movement execution.

It is assumed that the processing of a prime followed by a mask occurs sequentially in a feedforward manner when the three (initiation, takeover, and independence) criteria outlined by the rapid-chase theory are met. The purpose of the current study was to determine if the processing of the prime and mask fit the predictions of the rapid-chase theory when the prime and mask are presented during an ongoing movement. In two experiments, participants made rapid pointing movements to a target indicated by the mask. In Experiment 1, the prime was presented at movement onset and the prime-mask stimulus onset asynchrony (SOA) was manipulated. In Experiment 2, the prime-mask SOA was constant but the delay between movement and prime onset was manipulated. Although the results support the initiation and takeover criteria, the data did not support the independence criterion. Consequently, the rapid-chase theory does not appear to extend to movement execution.