Biology subjects

Hegele, M.

Publications and source records attributed to Hegele, M..

6 recordsLinked to original sources

bioRxiv2021

Direct and indirect cues can enable dual-adaptation, but through different learning processes

Switching between motor tasks requires accurate adjustments for changes in dynamics (grasping a cup) or sensorimotor transformations (moving a computer mouse). Dual-adaptation studies have investigated how learning of context-dependent dynamics or transformations is enabled by sensory cues. However, certain cues, such as color, have shown mixed results. We propose that these mixed results may arise from two major classes of cues: "direct" cues, which are part of the dynamic state and "indirect" cues, which are not. We hypothesized that explicit strategies would primarily account for adaptation for an indirect color cue but would be limited to simple tasks while a direct visual separation cue would allow implicit adaptation regardless of task complexity. To test this idea, we investigated the relative contribution of implicit and explicit learning in relation to contextual cue type (colored or visually shifted workspace) and task complexity (one or eight targets) in a dual-adaptation task. We found that the visual workspace location cue enabled adaptation across conditions primarily through implicit adaptation. In contrast, we found that the color cue was largely ineffective for dual-adaptation, except in a small subset of participants who appeared to use explicit strategies. Our study suggests that the previously inconclusive role of color cues in dual-adaptation may be explained by differential contribution of explicit strategies across conditions. New & NoteworthyWe present evidence that learning of context-dependent dynamics proceeds via different processes depending on the type of sensory cue used to signal the context. Visual workspace location enabled learning different dynamics implicitly, presumably because it directly enters the dynamic state estimate. In contrast, a color cue was only successful where learners were apparently able to leverage explicit strategies to account for changed dynamics. This suggests a unification for the previously inconclusive role of color cues.

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bioRxiv2021

Can Stephen Curry really know? - Conscious access to outcome prediction of motor actions

The NBA player Stephen Curry has a habit of turning away from the basket right after taking three-point shots, presumably because he can predict the success of his shot. For such a consciously accessible prediction to be possible, Stephen Curry needs access to internal processes of outcome prediction and valuation. Computational simulations and empirical data suggest that the quality of internal prediction processes is related to motor expertise. Whether the results of internal predictions can reliably be consciously accessed is less clear. In the current study, 30 participants each practiced a virtual goal-oriented throwing task for 1000 trials. Every second trial, they were required to verbally predict the success of the current throw. Results showed that on average, conscious prediction accuracy was above an individually computed chance level, taking into account individual success rates and response strategies. Furthermore, prediction accuracy was related to throwing performance. Participants with better performance predicted the success of their throws more accurately than participants with poorer performance. Moreover, for the poorer performing individuals, movement execution was negatively affected by the verbalized predictions required, and they did not show variation in speech characteristics (response latency) between correct and incorrect predictions. This indicates reduced quality of conscious access to internal processes of outcome prediction.

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bioRxiv2019

Prolonged reaction times eliminate residual errors in visuomotor adaptation

One persistent curiosity in visuomotor adaptation tasks is that participants often do not reach maximal performance. This incomplete asymptote has been explained as a consequence of obligatory computations within the implicit adaptation system, such as an equilibrium between learning and forgetting. A body of recent work has shown that in standard adaptation tasks, cognitive strategies operate alongside implicit learning. We reasoned that incomplete learning in adaptation tasks may primarily reflect a speed-accuracy trade-off on time-consuming motor planning. Across three experiments, we find evidence supporting this hypothesis, showing that hastened motor planning may primarily lead to under-compensation. When an obligatory waiting period was administered before movement start, participants were able to fully counteract imposed perturbations (experiment 1). Inserting the same delay between trials - rather than during movement planning - did not induce full compensation, suggesting that the motor planning interval predicts the learning asymptote (experiment 2). In the last experiment, we asked participants to continuously report their movement intent. We show that emphasizing explicit re-aiming strategies (and concomitantly increasing planning time) also lead to complete asymptotic learning. Findings from all experiments support the hypothesis that incomplete adaptation is, in part, the result of an intrinsic speed-accuracy trade-off, perhaps related to cognitive strategies that require parametric attentional reorienting from the visual target to the goal.

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bioRxiv2019

Explicit strategies in force field adaptation

In recent years, it has become increasingly clear that a number of learning processes are at play in visuomotor adaptation tasks. In addition to the presumed formation of an internal model of the perturbation, learners can also develop explicit knowledge allowing them to select better actions in responding to a given perturbation. Advances in visuomotor rotation experiments have underscored the important role that such \"explicit learning\" plays in shaping adaptation to kinematic perturbations. Yet, in adaptation to dynamic perturbations, its contribution has been largely overlooked, potentially because compensation of a viscous force field, for instance, is difficult to assess by commonly-used verbalization-based approaches. We therefore sought to assess the contribution of explicit learning in learners adapting to a dynamic perturbation by two novel modifications of a force field experiment. First, via an elimination approach, we asked learners to abandon any cognitive strategy before selected force channel trials to expose consciously accessible parts of overall learning. Learners indeed reduced compensatory force compared to standard Catch channels. Second, via a manual reporting approach, we instructed a group of learners to mimic their right hands adaptation by moving with their naive left hand. While a control group displayed negligible left-hand force compensation, the Mimic group reported forces that approximated right-hand adaptation but appeared to under-report the velocity component of the force field in favor of a more position-based component. We take these results to clearly demonstrate the contribution of explicit learning to force adaptation, underscoring its relevance to motor learning in general.\n\nNew & NoteworthyWhile the role of explicit learning has recently been appreciated in visuomotor adaptation tasks, their contribution to force field adaptation has not been as widely acknowledged. To address this issue, we employed two novel methods to assay explicit learning in force field adaptation tasks and found that learners can voluntarily control aspects of force production and manually report them with their untrained limb. This suggests that an explicit component contributes to force field adaptation and may provide alternative explanations to behavioral phenomena commonly thought to reveal a complex organization of internal models in the brain.

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bioRxiv2019

Of hands, tools, and exploding dots: How different action states and effects separate visuomotor memories

Humans can operate a variety of modern tools, which are often associated with different visuomotor transformations. Studies investigating this ability have repeatedly found that the simultaneous acquisition of different transformations appears inextricably tied to distinct states associated with movement, such as different postures or action plans, whereas abstract contextual associations can be leveraged by explicit aiming strategies. It still remains unclear how different transformations are remembered implicitly when target postures are similar. We investigated if features of planning to manipulate a visual tool, such as its visual identity or the intended effect enable implicit learning of opposing visuomotor rotations. Both cues only affected implicit aftereffects indirectly through generalization around explicit strategies. In contrast, practicing transformations with different hands resulted in separate aftereffects. It appears that different (intended) body states are necessary to separate aftereffects, supporting the idea that underlying implicit adaptation is limited to the recalibration of a body model.

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bioRxiv2018

Plan-based generalization shapes local implicit adaptation to opposing visuomotor transformations.

The human ability to use different tools demonstrates our capability of forming and maintaining multiple, context specific motor memories. Experimentally, this ability has been investigated in dual adaptation, where participants adjust their reaching movements to opposing visuomotor transformations. Adaptation in these paradigms occurs by distinct processes, i.e. the development of explicit aiming strategies for each transformation and/or the implicit acquisition of distinct visuomotor mappings. The presence of distinct, transformation-dependent aftereffects has been interpreted as support for the latter. Alternatively, however, distinct aftereffects could reflect adaptation of a single visuomotor map, which is locally adjusted in different regions of the workspace. Indeed, recent studies suggest that explicit aiming strategies direct where in the workspace implicit adaptation occurs.\n\nDisentangling these possibilities is critical to understanding how humans acquire and maintain separate motor memories for different skills and tools. We therefore investigated generalization of explicit and implicit adaptation to different directions after participants practiced two opposing cursor rotations, which were associated with separate visual workspaces. Whereas participants learned to compensate opposing rotations by explicit strategies that were specific to the visual workspace cue, aftereffects were not sensitive to visual workspace cues. Instead, aftereffects displayed bimodal generalization patterns that appeared to reflect locally limited learning of both transformations. By varying target arrangements and instructions, we show that these generalization patterns are consistent with implicit adaptation that generalizes locally around (explicit) movement plans associated with opposing visuomotor transformations. Our findings show that strategies can shape implicit adaptation in a complex manner.\n\nNew & NoteworthyVisuomotor dual adaptation experiments have identified contextual cues that enable learning of separate visuomotor mappings, but little is known about the underlying representations of learning. We report that visual workspace separation as a contextual cue enables participants to compensate opposing cursor rotations by a combination of explicit and implicit processes: Learners developed context-dependent explicit aiming strategies while an implicit visuomotor map represented dual adaptation independent from context by local adaptation around the explicit movement plan.

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