The temporal stability of visuomotor adaptation generalization

Abstract

Movement adaptation in response to systematic motor perturbations exhibits distinct spatial and temporal properties. These characteristics are typically studied in isolation, leaving the interaction largely unknown. Here we examined how the temporal decay of visuomotor adaptation influences the spatial generalization of the motor recalibration. First, we quantified the extent to which adaptation decayed over time. Subjects reached to a peripheral target, and a rotation was applied to the visual feedback of the unseen motion. The retention of this adaptation over different delays (0-120 s) ) decreased by 29.0 ± 6.8% at the longest delay and) was represented by a simple exponential, with a time constant of 22.5 ± 5.6 s. On the basis of this relationship we simulated how the spatial generalization of adaptation would change with delay. To test this directly, we trained additional subjects with the same perturbation and assessed transfer to 19 different locations (spaced 15° apart, symmetric around the trained location) and examined three delays (~4, 12, and 25 s). Consistent with the simulation, we found that generalization around the trained direction (±15°) significantly decreased with delay and distance, while locations >60° displayed near-constant spatiotemporal transfer. Intermediate distances (30° and 45°) showed a difference in transfer across space, but this amount was approximately constant across time. Interestingly, the decay at the trained direction was faster than that based purely on time, suggesting that the spatial transfer of adaptation is modified by concurrent passive (time dependent) and active (movement dependent) processes. Short-term motor adaptation exhibits distinct spatial and temporal characteristics. Here we investigated the interaction of these features, utilizing a simple motor adaptation paradigm (recalibration of reaching arm movements in response to rotated visual feedback). We examined the changes in the spatial generalization of motor adaptation for different temporal manipulations and report that the spatiotemporal generalization of motor adaptation is generally local and is influenced by both passive (time dependent) and active (movement dependent) learning processes.

Re-exposure to a sensorimotor perturbation produces opposite effects on explicit and implicit learning processes

“…[mean, 95% CI], 0.94, [0.88 1.00], Learning 2: 0.85, [0.74 0.96]). The small decay is likely due to some forgetting during the short break between these blocks (Hadjiosif and Smith, 2013;Hadjiosif et al, 2014;Zhou et al, 2017). Second, consistent with the hypothesis that participants aimed directly to the target throughout the experiment, reaction times were uniformly fast (~400 ms) and comparable across different phases of the experiment (Clamp vs Aftereffect: t(15)=0.810, p=0.430, BF10=0.340, d=0.20; Learning 1 vs Learning 2: t(15)=-0.390, p=0.702, BF10=0.273, d=-0.10).…”

Reduced transfer of visuomotor adaptation is associated with aberrant sense of agency in Schizophrenia

“…Zhou and colleagues (2017) found in healthy subjects that generalization around the trained direction (± 15°) significantly decreased with the delay between movements and distance from the trained target, while locations further away displayed near constant spatiotemporal transfer. In order to quantify this decrease, we first obtained measures of temporal decay of adaptation at the trained target location (0°) over the order of generalization probe trials (1 through 8 in the testing phase).…”

“…The experimental setup was similar to that used in Wu and Smith (2013) and Zhou and colleagues (2017). Subjects were seated at a desk in an adjustable chair facing a horizontal LCD monitor (BenQ XL2720T).…”

“…For instance, the spatial transfer generally decreases exponentially with the distance away from the trained direction, suggesting the underlying neural basis functions are rather narrow (Brayanov et al . 2012; Zhou et al . 2017).…”

Explicit strategies in force field adaptation

“…The other message read "Push", reminding participants of the instruction to "expect the robot to push you off and act as on those trials". We included this "Push" trial type as a control to ensure that any force modulation would be attributable to the associated instruction rather than other factors, such as delays introduced by the messages allowing a labile component of implicit memory to decay (Miyamoto et al 2014;Zhou et al 2017). Standard Catch channel trials were not preceded by a message.…”