Biology subjects

Henriques, D. Y. P.

Publications and source records attributed to Henriques, D. Y. P..

18 recordsLinked to original sources

bioRxiv2026

Vibrotactile stimulation on the upper back requires stronger vibration during goal-directed reaching but does not impede reaching performance

Vibrotactile stimulation is a promising method of biofeedback, with potential applications for ergonomic posture and balance, rehabilitation, and motor learning. These applications require balancing tactile perception with motor performance and cognitive workload. In this study, participants performed a detection task, a reaching task, and a concurrent reach-and-detect task, with vibrotactile signals delivered on the hand or upper back. Sensitivity to stimuli, motor performance, and cognitive workload were compared for each task. Sensitivity was suppressed during movement, but this suppression was greater on hand compared to the upper back. Movement time was slowed by vibration on the hand but not the upper back. Mental workload and task complexity increased for the reach-and-detect task compared to the individual tasks. We conclude that vibrotactile feedback devices worn on the upper back do not impede motor performance, with only minor tactile suppression. This could be overcome by presenting highly salient or personalized feedback.

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bioRxiv2026

Learning Environmental Dynamics: Building Internal Models of a Simulated External Force

Motor adaptation is typically studied using limb-based perturbations in highly constrained tasks. However, everyday actions require compensating for uncertain environmental dynamics impacting manipulated objects within redundant execution spaces, where multiple combinations of variables can achieve success. To investigate this, we designed a novel virtual reality task where participants launched a ball across a lateral water current to spatially distinct targets. Two experiments (2.0 m/s and 3.0 m/s) tested if classic adaptation signatures remain consistent across varying perturbation sizes. Results revealed three key signatures. First, participants exhibited robust error reduction to all targets during training. Second, between-subjects analyses revealed that this learning produced substantial, immediate transfer to untrained target locations. Finally, persistent motor aftereffects appeared upon perturbation removal, despite explicit cues indicating absence of the perturbation. Together, these results demonstrate that humans form internal models under altered projectile-environment dynamics, and that prior experience facilitates broad generalization across the workspace.

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bioRxiv2026

Rotation size drives heterogeneous explicit strategy development in motor adaptation

Humans rapidly adapt their movements to compensate for changes in the environment, yet how explicit movement strategies emerge during adaptation remains poorly understood. These strategies have traditionally been described by using a smooth, exponential learning curve, suggesting a relatively uniform pattern of strategy development across individuals (Taylor et al., 2014; McDougle et al., 2015). However, recent results suggest substantial variability in how individuals develop explicit aiming strategies, such as abrupt transitions (D'Amario et al., 2024; Townsend et al., 2026), or exploratory periods, or delayed stabilization of compensatory behaviour (Tsay et al., 2024), and some participants never developing a strategy. These findings raise the possibility that smooth group-averaged learning curves may obscure meaningful heterogeneity in individual strategy development. This study therefore examines whether explicit strategy development follows distinct individual-level patterns and whether these dynamics are influenced by perturbation size. Participants completed a visuomotor rotation reaching task where a cursor they controlled with their unseen, right hand was rotated around the home position using one of five perturbations (20, 30, 40, 50, and 60 degrees). Before each reach, participants reported their explicit strategy by aiming an arrow to indicate their planned hand movement direction. Based on previous findings, we hypothesized that participants would exhibit at least three distinct patterns of explicit strategy development emerged: 1) gradual/incremental, 2) stepwise, and 3) exploratory. Instead, participants were distributed along a continuum of strategy development profiles, with different regions along this continuum resembling these previous proposed patterns. Where learners fell along this continuum varied with perturbation magnitude, such that larger rotations associated with greater exploratory behaviour and proportion of strategy-use. Our findings reveal substantial heterogeneity in how explicit strategies emerge during visuomotor adaptation and suggest that smooth group-averaged learning curves may obscure important individual differences in learning dynamics. Notably, perturbation magnitude appears to systematically influence where individuals fall along this continuum, providing a potential mechanism for understanding how explicit strategies emerge and stabilize over time.

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bioRxiv2025

EEG Dynamics of Movement Preparation and Error Processing Distinguish Motor Adaptation From De Novo Learning

Previous research has distinguished behavioral mechanisms between motor adaptation and de novo learning. However, electroencephalography (EEG) markers dissociating them remain unclear. Here, participants (N = 32, 13 female) performed center-out reaching under a 30{degrees} fixed rotation (adaptation), mirror reversal (de novo learning), or random rotation (errors without learning), while we recorded EEG during movement preparation and post-movement feedback. We explored how perturbation type, training phase, and error magnitude shaped neural dynamics in both temporal and frequency domains. During preparation, the readiness potential (RP) showed opposite training-related modulation in the fixed and random rotations, suggesting increased reliance on updated internal models for adaptation. Mirror reversal training showed no RP change, likely reflecting reliance on effortful, explicit learning. Interestingly, we found that Lateralized Readiness Potentials (LRPs) reflected planned movement direction rather than effector-specific preparation. In the frequency domain, beta attenuation for large errors and alpha synchronization for small errors were more pronounced in the fixed rotation than in the mirror reversal, suggesting greater error-sensitivity during adaptation. During post-movement feedback, P3 amplitude decreased from early to late learning in the fixed and random rotations but remained stable in the mirror reversal, highlighting differences in cognitive demands across perturbations. A sustained late positivity emerged following small errors across perturbations, potentially indexing implicit learning. Random rotations also elicited distinct frontal and central beta modulation, likely reflecting disengagement due to task unpredictability. Together, we show that preparatory and feedback-related EEG signatures differ across perturbation types, revealing distinct neural mechanisms underlying motor adaptation and de novo learning. Significance statementUnderstanding how the brain supports skill acquisition and adaptation is critical for advancing theories and applications of motor learning. Although behavioral differences between motor adaptation and de novo learning are well established, the neural processes that distinguish them remain unclear. By comparing EEG activity during movement preparation and feedback-error processing across multiple perturbation types, we uncover distinct temporal and frequency domain signatures that uniquely characterize each learning process. Our findings show that adaptation engages neural dynamics consistent with updating internal models and error-processing, whereas de novo learning relies on explicit, cognitively demanding strategies that likely unfold over extended practice. These results provide a clear neural framework for distinguishing motor learning mechanisms.

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bioRxiv2025

Saturation, Task Error, and Feedback Timing Shape Early Implicit Adaptation

Motor adaptation is essential for maintaining coordination and precision in daily activities. Implicit motor adaptation--adaptation that occurs without conscious awareness--is thought to be primarily driven by sensory prediction errors. Here, we investigated how rapidly these unconscious changes in reaching behavior emerge as a function of error magnitude and the availability of task error signals. To this end, we employed a single-trial learning (STL) paradigm within a classical visuomotor rotation task. Participants made center-out reaching movements to either small (dot) or large (arc) targets while experiencing single perturbation trials with cursor rotations ranging from 1{degrees} to 90{degrees}, each followed by an aligned washout trial. By manipulating target size, we systematically modulated the presence of task error while holding sensory prediction error constant. We further compared these early implicit changes with those observed during standard prolonged adaptation to a fixed 20{degrees} rotation across >100 trials. Our results show that implicit adaptation emerges rapidly, even after a single exposure to small perturbations, and follows a saturating, fixed-rate response profile. Importantly, the magnitude of single-trial adaptation was greater when task error was present (small targets) compared with conditions in which only sensory prediction error was available (large targets). Moreover, STL-derived parameters moderately predicted the initial phase of adaptation during prolonged learning, suggesting that STL captures core dynamics of early implicit processes. These findings provide new insight into the mechanistic principles governing implicit motor adaptation. By identifying the parameters that drive early-stage error-based learning, this work refines current models of sensorimotor learning and highlights potential strategies for designing targeted training or rehabilitation protocols that leverage rapid adaptation processes to enhance motor performance and recovery.

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bioRxiv2025

Modeling Human Visuomotor Adaptation with a DisturbanceObserver Framework

A fundamental problem of visuomotor adaptation research is to understand how the brain is capable to asymptotically remove a predictable exogenous disturbance from a visual error signal using limited sensor information by re-calibration of hand movement. From a control theory perspective, the most striking aspect of this problem is that it falls squarely in the realm of the internal model principle of control theory. Despite this fact, the relationship between the internal model principle and models of visuomotor adaptation is currently not well developed. This paper aims to close this gap by proposing an abstract discrete-time state space model of visuomotor adaptation based on the internal model principle. The proposed DO Model, a metonym for its most important component, a disturbance observer, addresses key modeling requirements: modular architecture, physically relevant signals, parameters tied to atomic behaviors, and capacity for abstraction. The two main computational modules are a disturbance observer, a recently developed class of internal models, and a feedforward system that learns from the disturbance observer to improve feedforward motor commands. Author summaryA central research challenge in the field of motor learning is to disentangle the components of motor learning [1-8]. The main hypothesis explored in this paper is that visuomotor rotation experiments in which participants are given distinct instructions to either move the hand or the cursor to the target offer a platform to explore two components of motor learning arising from different computations and possibly different brain regions. The two computations correspond to a disturbance observer whose role is to detect and then eliminate environmental perturbations and a feedforward system whose role is to learn from the disturbance observer to improve feedforward motor commands.

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bioRxiv2024

Implicit Adaptation is Fast, Robust and Independent from Explicit Adaptation

During classical visuomotor adaptation, the implicit process is believed to emerge rather slowly; however, recent evidence has found this may not be true. Here, we further quantify the time-course of implicit learning in response to diverse feedback types, rotation magnitudes, feedback timing delays, and the role of continuous aiming on implicit learning. We find that implicit learning unfolds at a higher rate than conventionally expected in all feedback conditions. Increasing rotation size not only raises asymptotes, but also generally heightens explicit awareness, with no discernible difference in implicit rates. Cursor-jump and terminal feedback, with or without delays, predominantly enhance explicit adaptation while slightly diminishing the extent or the speed of implicit adaptation. In a continuous aiming reports condition, there is no discernible impact on implicit adaptation, and implicit and explicit adaptation progress at indistinguishable speeds. Finally, investigating the assumed negative correlation as an indicator of additivity of implicit and explicit processes, we observe weak associations at best across conditions. Our observation of implicit learning early in training in all tested conditions signifies how fast and robust our innate adaptation system is.

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bioRxiv2024

Motor adaptation to environment changes predicting object behaviour can be flexible and implicit.

The human motor system can adapt to perturbations by updating existing models of motor control or by creating context-specific motor memories or strategies. We investigate if motor adaptation is context-informed when a perturbation is applied to either the throw direction of a ball, or the acceleration of the ball post-release during a virtual throw-to-target task. Using the visual slant of the task surface in an immersive virtual environment, we determine if the tendency for model updating is influenced by informative visual cues that predict perturbations to intended actions. Our findings reveal that perturbations resembling accelerations enabled flexible motor adaptation regardless of the presence of the slant cue. Perturbations in the throw direction conversely led to internal model updating. Additionally, visual slant properties of the task surface elicited implicit, slant-specific changes in performance. Our findings underscore the role of visual properties of both perturbations and environments in flexible motor learning.

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bioRxiv2023

Task-relevant object shape properties act as poor but viable cues for the attribution of motor errors to external objects

When a context change is detected during motor learning, motor memories - internal models for executing movements within some context - may be created or existing motor memories may be activated and modified. Assigning credit to plausible causes of errors can allow for fast retrieval and activation of a motor memory, or a combination of motor memories, when the presence of such causes is detected. Features of the movement-context intrinsic to the movement dynamics, such as posture of the end effector, are often effective cues for detecting context change whereas features extrinsic to the movement dynamics, such as the colour of an object being moved, are often not. These extrinsic cues are typically not relevant to the motor task at hand and can be safely ignored by the motor system. We conducted two experiments testing if extrinsic but task-relevant object-shape cues during an object- transport task can act as viable contextual cues for error assignment to the object, and the creation of new, object-shape-associated motor memories. In the first experiment we find that despite the object- shape cues, errors are primarily attributed to the hand transporting the object. In a second experiment, we find that although participants can execute differing movements cued by the object shape in a dual adaptation task, they primarily use explicit strategies to do so.

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bioRxiv2022

Adapting to visuomotor rotations in stepped increments increases implicit motor learning

Human motor adaptation relies on both explicit conscious strategies and implicit unconscious updating of internal models to correct motor errors. Implicit adaptation is powerful, requiring less preparation time before executing adapted movements, but recent work suggests it is limited to some absolute magnitude regardless of the size of a visuomotor perturbation when the perturbation is introduced abruptly. It is commonly assumed that gradually introducing a perturbation should lead to improved implicit learning beyond this limit, but outcomes are conflicting. We tested whether introducing a perturbation in two distinct gradual methods can overcome the apparent limit and explain past conflicting findings. We found that gradually introducing a perturbation in a stepped manner, where participants were given time to adapt to each partial step before being introduced to a larger partial step, led to [~]80% higher implicit aftereffects of learning, but introducing it in a ramped manner, where participants adapted larger rotations on each subsequent reach, did not. Our results clearly show that gradual introduction of a perturbation can lead to substantially larger implicit adaptation, as well as identify the type of introduction that is necessary to do so.

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bioRxiv2022

Measures of Implicit and Explicit Adaptation Do Not Linearly Add

Moving effectively is essential for any animal. Thus, many different kinds of brain processes likely contribute to learning and adapting movement. How these contributions are combined is unknown. Nevertheless, the field of motor adaptation has been working under the assumption that measures of explicit and implicit motor adaptation can simply be added in total adaptation. While this has been tested, we show that these tests were insufficient. We put this additivity assumption to the test in various ways, and find that measures of implicit and explicit adaptation are not additive. This means that future studies should measure both implicit and explicit adaptation directly. It also challenges us to disentangle how various motor adaptation processes do combine when producing movements, and may have implications for our understanding of other kinds of learning as well. (data and code: https://osf.io/dh86e)

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bioRxiv2022

Rapid motor adaptation to bounce perturbations in online Pong game is independent from the visual tilt of the bouncing surface

Motor adaptation describes the ability of the motor system to counteract repeated perturbations in order to reduce movement errors. Most research in the field investigated adaptation in response to perturbations affecting the moving hand. Fewer studies looked at the effect of a perturbation applied to the movement target, however they used simplistic visual stimuli. In this study, we examined motor adaptation to perturbations affecting the motion of dynamic targets. In addition, we asked whether external visual cues in the environment could facilitate this process. To do so, participants were asked to play an online version of the Pong game in which they intercepted a ball bouncing off a wall using a paddle. A perturbation was applied to alter the post-bounce trajectory of the ball and the wall orientation was manipulated to be consistent or not with the ball trajectory. The "trained tilt" group (n = 34) adapted to the consistent condition and the "trained horizontal" group (n = 36) adapted to the inconsistent condition. In case participants optimally integrate external visual cues, the "trained tilt" group is expected to exhibit faster and/or more complete adaptation than the "trained horizontal" group. We found that the perturbation reduced interception accuracy. Participants showed large interception errors when the perturbation was introduced, followed by rapid error decrease and aftereffects (errors in the opposite direction) once the perturbation was removed. Although both experimental groups showed these typical markers of motor adaptation, we did not find differences in interception success rates or errors between the "trained tilt" and "trained horizontal" groups. Our results demonstrate that participants quickly adapted to the dynamics of the pong ball. However, the visual tilt of the bouncing surface did not enhance their performance. The present study highlights the ability of the motor system to adapt to external perturbations applied to a moving target in a more dynamical environment and in online settings. These findings underline the prospects of further research on sensorimotor adaptation to unexpected changes in the environment using more naturalistic and complex real-world or virtual reality tasks as well as gamified paradigms.

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bioRxiv2022

Reduced feedback barely slows down proprioceptive recalibration

Introducing altered visual feedback of the hand results in quick adaptation of reaching movements. And while this may be partly due to explicit strategies, our lab has shown that implicit changes like reach aftereffects and shift in estimates of the unseen hand, can also emerge and even saturate within a few training trials. The goal of the current study is to determine whether these rapid changes in unseen hand position that occur during classical visuomotor adaptation are diminished or slowed when feedback during training is reduced. We reduced feedback by either providing visual feedback only at the end of the reach (terminal feedback) or constraining hand movements to reduce efferent contribution (exposure). We measured changes as participants completed reaches with a 30{degrees} rotation, a -30{degrees} rotation and clamped visual feedback, with these two "impoverished" training conditions, along with classical visuomotor adaptation training, while continuously estimating their felt hand position. Classic continuous-cursor training produced exemplary learning curves and rapid and robust shifts in felt hand position. Training with terminal feedback slightly reduced the initial rate of change in overall adaptation and but not the magnitude of shifts in felt hand position. Finally using a robot to constrain and deviate hand movement direction, called exposure training, only delayed saturation of proprioceptive changes by a single trial and these changes were slightly smaller than those during classical training. Taken together, adaptation and shifts in felt hand position are a rapid and robust responses to sensory mismatches and are only slightly modulated when feedback is reduced. This means that, given a visuo-proprioceptive mismatch, the resulting shift in sense of limb position can contribute to movements from the start of adaptation.

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bioRxiv2021

Measuring the double-drift illusion with hand tracking

If a gabor pattern drifts in one direction while its internal texture drifts in the orthogonal direction, its perceived position deviates further and further away from its true path. We first evaluated the illusion using manual tracking. Participants followed the gabor with a stylus on a drawing tablet that coincided optically with the horizontal monitor surface. Their hand and the stylus were not visible during the tracking. The magnitude of the tracking illusion corresponded closely to previous perceptual and pointing measures indicating that manual tracking is a valid measure for the illusion. This allowed us to use it in a second experiment to capture the behavior of the illusion as it eventually degrades and breaks down in single trials. Specifically, the deviation of the gabor stops accumulating at some point and either stays at a fixed offset or resets toward the veridical position. To report the perceived trajectory of the gabor, participants drew it after the gabor was removed from the monitor. Resets were detected and analyzed and their distribution matches neither a temporal nor a spatial limit, but rather a broad gamma distribution over time. This suggests that resets are triggered randomly, about once per 1.3 s, possible by extraneous distractions or eye movements.

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bioRxiv2021

Proprioceptive imprecision in Ehlers-Danlos Syndrome does not affect the extent of sensorimotor plasticity

PurposeTo explore the effect of joint hypermobility on acuity, and plasticity, of hand proprioception. Materials and MethodsWe compared proprioceptive acuity between EDS patients and controls. We then measured any changes in their estimate of hand position after participants adapted their reaches in response to altered visual feedback of their hand. The Beighton Scale was used to quantify the magnitude of joint hypermobility. ResultsThere were no differences between the groups in the accuracy of estimates of hand location, nor in the visually-induced changes in hand location. However, EDS patients estimates were less precise when based purely on proprioception and could be partially predicted by Beighton score. ConclusionsEDS patients are less precise at estimating their hands location when only afferent information is available, but the presence of efferent signalling may reduce this imprecision. Those who are more hypermobile are more likely to be imprecise.

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bioRxiv2020

Implicit learning is too fast to be a slow process

In motor learning, the slow development of implicit learning is traditionally taken for granted. While much is known about training performance during adaptation to a perturbation in reaches, saccades and locomotion, little is known about the time course of the underlying implicit processes during normal motor adaptation. Implicit learning is characterized by both changes in internal models and state estimates of limb position. Here, we measure both as reach aftereffects and shifts in hand localization in our participants, after every training trial. The observed implicit changes were near asymptote after only one to three perturbed training trials and were not predicted by a two-rate models slow process that is supposed to capture implicit learning. Hence, we show that implicit learning is much faster than conventionally believed, which has implications for rehabilitation and skills training.

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bioRxiv2020

External error attribution dampens efferent-basedpredictions but not proprioceptive changes in handlocalization

In learning and adapting movements in changing conditions, people attribute the errors they experience to a combined weighting of internal or external sources. As such, error attribution that places more weight on external sources should lead to decreased updates in our internal models for movement of the limb or estimating the position of the effector, i.e. there should be reduced implicit learning. However, measures of implicit learning are the same whether or not we induce explicit adaptation with instructions about the nature of the perturbation. Here we evoke clearly external errors by either demonstrating the rotation on every trial, or showing the hand itself throughout training. Implicit reach aftereffects persist, but are reduced in both groups. Only for the group viewing the hand, changes in hand position estimates suggest that predicted sensory consequences are not updated, but only rely on recalibrated proprioception. Our results show that estimating the position of the hand incorporates source attribution during motor learning, but recalibrated proprioception is an implicit process unaffected by external error attribution.

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bioRxiv2018

The effects of awareness of the perturbation during motor adaptation on hand localization

Explicit awareness of a task is often evoked during rehabilitation and sports training with the intention of accelerating learning and improving performance. However, the effects of awareness of perturbations on the resulting sensory and motor changes produced during motor learning are not well understood. Here, we use explicit instructions as well as large rotation sizes to generate awareness of the perturbation during a visuomotor rotation task and test the resulting changes in both perceived and predicted sensory consequences as well as implicit motor changes.\n\nWe split participants into 4 groups which differ in both magnitude of the rotation (either 30{degrees} or 60{degrees}) during adaptation, and whether they receive a strategy to counter the rotation or not prior to adaptation. Performance benefits of explicit instruction are largest during early adaptation but continued to lead to improved performance through 90 trials of training. We show that with either instruction, or with large perturbations, participants become aware of countering the rotation. However, we find a base amount of implicit learning, with equal magnitudes, across all groups, even when asked to exclude any strategies while reaching with no visual feedback of the hand.\n\nParticipants also estimate the location of the unseen hand when it is moved by the robot (passive localization) and when they generate their own movement (active localization) following adaptation. These learning-induced shifts in estimates of hand position reflect both proprioceptive recalibration and updates in the predicted consequences of movements. We find that these estimates of felt hand position, which reflect updates in both proprioception and efference based estimates of hand position, shift significantly for all groups and were not modulated by either instruction or perturbation size.\n\nOur results indicate that not all processes of motor learning benefit from an explicit awareness of the task. Particularly, proprioceptive recalibration and the updating of predicted sensory consequences are largely implicit processes.

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