Variance in exposed perturbations impairs retention of visuomotor adaptation

Abstract

Sensorimotor control requires an accurate estimate of the state of the body. The brain optimizes state estimation by combining sensory signals with predictions of the sensory consequences of motor commands using a forward model. Given that both sensory signals and predictions are uncertain (i.e., noisy), the brain optimally weights the relative reliance on each source of information during adaptation. In support, it is known that uncertainty in the sensory predictions influences the rate and generalization of visuomotor adaptation. We investigated whether uncertainty in the sensory predictions affects the retention of a new visuomotor relationship. This was done by exposing three separate groups to a visuomotor rotation whose mean was common at 15° counterclockwise but whose variance around the mean differed (i.e., SD of 0°, 3.2°, or 4.5°). Retention was assessed by measuring the persistence of the adapted behavior in a no-vision phase. Results revealed that mean reach direction late in adaptation was similar across groups, suggesting it depended mainly on the mean of exposed rotations and was robust to differences in variance. However, retention differed across groups, with higher levels of variance being associated with a more rapid reversion toward nonadapted behavior. A control experiment ruled out the possibility that differences in retention were accounted for by differences in success rates. Exposure to variable rotations may have increased the uncertainty in sensory predictions, making the adapted forward model more labile and susceptible to change or decay. The brain predicts the sensory consequences of motor commands through a forward model. These predictions are subject to uncertainty. We use visuomotor adaptation and modulate uncertainty in the sensory predictions by manipulating the variance in exposed rotations. Results reveal that variance does not influence the final extent of adaptation but selectively impairs the retention of motor memories. These results suggest that a more uncertain forward model is more susceptible to change or decay.

Eye movements do not play an important role in the adaptation of hand tracking to a visuomotor rotation

“…The case of adaptation to a visuomotor rotation, a situation in which the visual feedback of hand movements is rotated, has been thoroughly studied over the last decades (Cunningham 1989;Krakauer 2009;Ogawa and Imamizu 2013;Prablanc et al 1975;Scheidt and Ghez 2007). Although this field of research has produced substantial knowledge about the generalization of adaptation and consolidation of motor memory (Canaveral et al 2017;Huang et al 2011;Orban de Xivry and Lefèvre 2015), little is known about the possible contribution of eye movements to visuomotor adaptation despite the intricate relationship that is believed to exist between eye and hand movements (Crawford et al 2004;Miall et al 2001;Neggers and Bekkering 2000;Prablanc et al 1979). The goal of the current study is to explore this issue.…”

Artificial Joint Speed Feedback for Myoelectric Prosthesis Controls

“…Perturbation adaptation of the Euclidean distance between the cursor and the target was estimated using an exponential decay model [40]–[42]: where t is the number of trials after perturbation onset, α is the gain indicating the immediate increase in error upon perturbation, and λ is the decay rate indicating the speed at which the error converges to the baseline error ɛ ∞ .…”

“…Perturbation adaptation of the Euclidean distance between the cursor and the target was estimated using an exponential decay model [40]- [42]:…”

“…Exponential decay is a useful model for describing motor adaptation to perturbations, as each parameter quantifies a different aspect of the reaching behavior over time [40]- [42]. Offset describes the error rate that reaches converge to following many trials, Gain describes the initial jump in error at the onset of the perturbation compared to the Offset, and Rate describes how quickly error falls from the initial error to the Offset value.…”

Luring the Motor System: Impact of Performance-Contingent Incentives on Pre-Movement Beta-Band Activity and Motor Performance

“…Moreover, because all experiments were conducted in the dark, the semi-silvered mirror prevented participants from seeing their hand during the experiment. This setup has been used in previously published work (Benazet et al, 2016;Canaveral et al, 2017;Hamel et al, 2017;Hamel-Thibault et al, 2018).…”