The absence or temporal offset of visual feedback does not influence adaptation to novel movement dynamics

Delays in transmitting and processing sensory information require correctly associating delayed feedback to issued motor commands for accurate error compensation. The flexibility of this alignment between motor signals and feedback has been demonstrated for movement recalibration to visual manipulations, but the alignment dependence for adapting movement dynamics is largely unknown. Here we examined the effect of visual feedback manipulations on force-field adaptation. Three subject groups used a manipulandum while experiencing a lag in the corresponding cursor motion (0, 75 or 150 ms). When the offset was applied at the start of the session (continuous condition) adaptation was not significantly different between groups. However, these similarities may be due to acclimation to the offset prior to motor adaptation. We tested additional subjects that experienced the same delays concurrent with the introduction of the perturbation (abrupt condition). In this case adaptation was statistically indistinguishable from the continuous condition, indicating that acclimation to feedback delay was not a factor. In addition, endpoint errors were not significantly different across the delay or onset conditions, but endpoint correction (e.g., deceleration duration) was influenced by the temporal offset. As an additional control, we tested a group of subjects that performed without visual feedback and found comparable movement adaptation results. These results suggest that visual feedback manipulations (the absence or temporal misalignment) does not affect adaptation to novel dynamics, independent of both acclimation and perceptual awareness. These findings could have implications for modeling how the motor system adjusts to errors despite concurrent delays in sensory feedback information.

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