Biology subjects

Ivry, R. B.

Publications and source records attributed to Ivry, R. B..

At least 19 recordsLinked to original sources

bioRxiv2026

Development of appropriate sensorimotor recalibration for a de novo skill

Implicit adaptation operates automatically to ensure that well-learned movements remain exquisitely calibrated. A long-standing puzzle is how this process is applied when learning a new skill: Prior work has highlighted that implicit recalibration is inflexible, even when its operation results in maladaptive behavior given the sensorimotor mapping required for the new skill. Here, we revisited this problem, training participants for up to a month on a range of tasks with novel mappings, including mirror reversals and large rotations. Contrary to previous findings, implicit recalibration was flexibly reconfigured after prolonged training in a manner appropriate for each novel mapping. Training that emphasized feedforward planning rather than feedback control was sufficient to induce this reconfiguration. Learning involved reconfiguration of the sensory predictions and error correction policy for the new mapping, and participants were able to switch between mappings with minimal interference. These results demonstrate that implicit recalibration is reconfigured during skill acquisition, enabling flexible, context-specific adaptation.

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bioRxiv2026

Attention warps visual-semantic representations across the human cerebellum

Humans effortlessly shift their attention between objects and events in the environment. These attentional shifts modulate the representation of information in many regions of the cerebral cortex, including those that represent visual-semantic information. Based on recent evidence that the cerebellum also represents semantic information, we hypothesized that attention would also shift semantic representations in the cerebellum. To test this hypothesis, we used fMRI to measure brain activity while participants watched naturalistic movie clips and were instructed to attend to either people or vehicles. We used a voxelwise encoding model framework to recover visual-semantic representations in the cerebral cortex and cerebellum under the two conditions, and quantified the direction and magnitude of visual-semantic tuning shifts between conditions. Attention to different semantic categories had a large effect on visual-semantic tuning in the cerebellum. Representations in some regions shifted toward the attended category, and representations in other regions shifted away from the attended category. Within cerebellar regions that best represent visual-semantic information, the tuning shifts were most pronounced in Crus I and II and in lobule VI. Further, the magnitude of attentional tuning shifts was greater in the cerebellum than in the cerebral cortex, particularly for tuning shifts towards the attended category. These differences suggest that attentional modulation in the cerebellum is different than in the cerebral cortex and may not solely be driven by cerebral inputs.

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bioRxiv2026

Impaired representation of temporal statistics in cerebellar degeneration

The nervous system represents the statistical structure of the environment to facilitate perception. In time perception, exploiting prior information through Bayesian inference reduces the influence of perceptual noise. However, the neural substrate underlying this computation remains unknown. The cerebellum is a strong candidate whose integrity is essential for motor and perceptual tasks requiring precise timing, and rodent physiological studies indicate that cerebellar plasticity mechanisms can support the encoding of temporal statistics. To examine how the cerebellum is involved in Bayesian timing, we tested patients with cerebellar degeneration and matched controls on duration reproduction tasks with varying prior distributions. Patients showed the signatures of Bayesian inference, but with greater timing variability, stronger regression toward the mean, and slower updating of the prior. We developed a model of the cerebellar microcircuit in which Purkinje cell plasticity over a granule cell temporal basis set provides a shared substrate for the prior and the inference. Simulations of cerebellar degeneration showed deficits consistent with the behavioral changes observed in the patients. These results suggest a critical role for the human cerebellum in Bayesian inference, with the system generating optimally timed behavior across varying contexts and even remaining robust under extensive neuropathology.

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bioRxiv2026

Dissociable thalamic oscillatory mechanisms support motor sequence learning

The ventrointermediate nucleus of the thalamus (VIM) is implicated in motor sequence learning, yet the underlying neural mechanisms remain unclear. We recorded intracranial activity from the human VIM during a serial reaction time task to determine how neural dynamics support learning. Participants responded faster during repeating than randomized sequences. Beta-to-low-gamma activity was greater during repeating sequences and elevated relative to the prestimulus baseline, consistent with emergence and stabilization of learned motor representations. In contrast, beta-phase modulation of high-frequency activity decreased progressively from rest to random to repeated sequence execution. Stronger phase-amplitude coupling was associated with faster responses, reaching significance in the random condition. These findings reveal a dissociation between power and cross-frequency coupling. Together they suggest that thalamic dynamics contribute to motor learning through multiple mechanisms: beta-band power reflects the emergence of learned motor representations, whereas beta-high-frequency coupling is enhanced when the context is less predictable.

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bioRxiv2026

Manipulating speech perception with amplitude-modulated kilohertz magnetic perturbation (AM-kTMP)

Speech perception has been hypothesized to exploit neural activity that entrains to the rhythmic properties of the utterance. Perceptual sensitivity varies with the phase of oscillatory activity induced by speech, and with an external oscillatory perturbation induced by transcranial alternating current stimulation (tACS) over the temporal lobe. Here we used a new form of non-invasive brain stimulation (NIBS), kilohertz transcranial magnetic perturbation (kTMP), in which a low frequency perturbation is created by the amplitude modulation (AM) of a continuous high-frequency carrier signal (3.5 kHz). As a magnetic induction method, kTMP can produce much higher electrical fields at the cortical surface than tACS and reduces cutaneous co-stimulation. Human participants (n=40) listened to sequences of rhythmic speech while receiving kTMP with an AM component of 3.125 Hz. The phasic modulation of perceptual sensitivity was greater during AM-kTMP than during sham stimulation, suggesting that AM-kTMP entrains neural activity underlying speech perception. Participants ratings of rhythmic sensations and other side effects did not differ between AM-kTMP and sham stimulation. Together with its reduced peripheral stimulation, our results highlight kTMP as a promising NIBS method for modulating frequency-specific brain dynamics in speech perception.

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bioRxiv2026

Amplitude-Modulated Kilohertz Stimulation Targeting Beta-Band Activity Disrupts Motor Learning

Sensorimotor learning is associated with the modulation of neural rhythms in the primary motor cortex (M1). Beta-band activity ("beta"; 15-30 Hz) is suppressed during learning, while delta oscillations (1-4 Hz) become increasingly correlated with movement kinematics as skill improves. These observations have been complemented by experimental manipulations designed to perturb oscillatory activity with externally applied electric fields (E-fields). In non-human primates, invasive beta stimulation has been shown to disrupt motor learning whereas delta stimulation enhanced motor recovery in a stroke model. Causal evidence in humans remains limited, partly because established non-invasive methods cannot achieve continuous, narrowband E-fields at sufficient amplitude in the brain. To address this gap, we employed kilohertz transcranial magnetic perturbation (kTMP), a non-invasive magnetic induction technique that delivers continuous narrowband kilohertz E-fields which can be amplitude-modulated (AM) to target cortical rhythms. We applied AM-kTMP to test the functional relevance of beta and delta activity in human motor learning. In a double-blind mixed design, 40 participants performed a force-control task while receiving AM-kTMP at E-field amplitudes of 8 V/m in M1. We targeted either beta or delta, each paired with a sham condition. AM-kTMP influenced motor performance in a frequency-dependent manner: Beta-kTMP suppressed performance gains relative to both delta-kTMP and sham, whereas delta-kTMP showed no effect. These results suggest that increased beta activity in human M1 can interfere with motor learning. More broadly, kTMP offers a novel approach to probe frequency-specific cortical dynamics.

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bioRxiv2025

Distinct Implicit Contributions to Action Selection and Action Execution in Sensorimotor Adaptation

The sensorimotor system is continuously adjusted to minimize error. Current theories assume that this adaptation process entails the operation of multiple learning systems, with a key division between implicit and explicit components. Recent studies have revealed several inconsistencies regarding the characteristics and constraints of the implicit system, suggesting that the current framework is incomplete. Here, we propose that these conflicting findings can be understood by recognizing that there are multiple implicit subcomponents, distinguished by their distinct computational goals. One well-studied component is implicit recalibration, a process critical for action execution which uses sensory-prediction errors to automatically refine the sensorimotor map. Here we describe a second, novel component, implicit aiming, a process which contributes to action selection to achieve the specific goals. Through a series of studies, we find compelling evidence that those two implicit processes show a clear separation in their temporal stabilities and contextual modulations. These distinct properties correspond to different computational frameworks attributing learning dynamics to either contextual inference or cancellation of competing neural populations, respectively. Together, these findings suggest an alternative framework for sensorimotor adaptation based on the computational goals of the system rather than phenomenology.

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bioRxiv2024

Attention defines the context for implicit sensorimotor adaptation

Movement errors are used to continuously recalibrate the sensorimotor map, a process known as sensorimotor adaptation. Here we examined how attention influences this automatic and obligatory learning process. Focusing first on spatial attention, we compared conditions in which the visual feedback that provided information about the movement outcome was either attended or unattended. Surprisingly, this manipulation had no effect on the rate of adaptation. We next used a dual-task methodology to examine the influence of attentional resources on adaptation. Here, again, we found no effect of attention, with the rate of adaptation similar under focused or divided attention conditions. Interestingly, we found that attention modulates adaptation in an indirect manner: Attended stimuli serve as cues that define the context for learning. The rate of adaptation was significantly attenuated when the attended stimulus changed from the end of one trial to the start of the next trial. In contrast, similar changes to unattended stimuli had no impact on adaptation. Together, these results suggest that visual attention defines the cues that establish the context for sensorimotor learning.

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bioRxiv2024

Differential Aging Effects on Implicit and Explicit Sensorimotor Learning

Deterioration in motor control is a hallmark of aging, significantly contributing to a decline in quality of life. More controversial is the question of whether and how aging impacts sensorimotor learning. We hypothesized that the inconsistent picture observed in the current literature can be attributed to at least two factors. First, aging studies tend to be underpowered. Second, the learning assays used in these experiments tend to reflect, to varying degrees, the operation of multiple learning processes, making it difficult to make inferences across studies. We took a two-pronged approach to address these issues. We first performed a meta-analysis of the sensorimotor adaptation literature focusing on outcome measures that provide estimates of explicit and implicit components of adaptation. We then conducted two well-powered experiments to re-examine the effect of aging on sensorimotor adaptation, using behavioral tasks designed to isolate explicit and implicit processes. Convergently, both approaches revealed a striking dissociation: Older individuals exhibited a marked impairment in their ability to discover an explicit strategy to counteract a visuomotor perturbation. However, they exhibited enhanced implicit recalibration. We hypothesize that the effect of aging on explicit learning reflects an age-related decline in reasoning and problem solving, and the effect of aging on implicit learning reflects age-related changes in multisensory integration. Taken together, these findings deepen our understanding of the impact of aging on sensorimotor learning.

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bioRxiv2024

Motor adaptation is reduced by symbolic compared to sensory feedback

Motor adaptation - the process of reducing motor errors through feedback and practice - is an essential feature of human competence, allowing us to move accurately in dynamic and novel environments. Adaptation typically results from sensory feedback, with most learning driven by visual and proprioceptive feedback that arises with the movement. In humans, motor adaptation can also be driven by symbolic feedback. In the present study, we examine how implicit and explicit components of motor adaptation are modulated by symbolic feedback. We conducted three reaching experiments involving over 400 human participants to compare sensory and symbolic feedback using a task in which both types of learning processes could be operative (Experiment 1) or tasks in which learning was expected to be limited to only an explicit process (Experiments 2 and 3). Adaptation with symbolic feedback was dominated by explicit strategy use, with minimal evidence of implicit recalibration. Even when matched in terms of information content, adaptation to rotational and mirror reversal perturbations was slower in response to symbolic feedback compared to sensory feedback. Our results suggest that the abstract and indirect nature of symbolic feedback disrupts strategic reasoning and/or refinement, deepening our understanding of how feedback type influences the mechanisms of sensorimotor learning.

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bioRxiv2024

Interference underlies attenuation upon relearning in sensorimotor adaptation

Savings refers to the gain in performance upon relearning a task. In sensorimotor adaptation, savings is tested by having participants adapt to perturbed feedback and, following a washout block during which the system resets to baseline, presenting the same perturbation again. While savings has been observed with these tasks, we have shown that the contribution from implicit sensorimotor adaptation, a process that uses sensory prediction errors to recalibrate the sensorimotor map, is actually attenuated upon relearning (Avraham et al., 2021). In the present study, we test the hypothesis that this attenuation is due to interference arising from the washout block, and more generally, from experience with a different relationship between the movement and the feedback. In standard adaptation studies, removing the perturbation at the start of the washout block results in a salient error signal in the opposite direction to that observed during learning. As a starting point, we replicated the finding that implicit adaptation is attenuated following a washout period in which the feedback now signals a salient opposite error. When we eliminated visual feedback during washout, implicit adaptation was no longer attenuated upon relearning, consistent with the interference hypothesis. Next, we eliminated the salient error during washout by gradually decreasing the perturbation, creating a scenario in which the perceived errors fell within the range associated with motor noise. Nonetheless, attenuation was still prominent. Inspired by this observation, we tested participants with an extended experience with veridical feedback during an initial baseline phase and found that this was sufficient to cause robust attenuation of implicit adaptation during the first exposure to the perturbation. This effect was context-specific: It did not generalize to movements that were not associated with the interfering feedback. Taken together, these results show that the implicit sensorimotor adaptation system is highly sensitive to memory interference from a recent experience with a discrepant action-outcome contingency.

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bioRxiv2024

The Origin of Movement Biases During Reaching

Goal-directed movements can fail due to errors in our perceptual and motor systems. While these errors may arise from random noise within these sources, they also reflect systematic motor biases that vary with the location of the target. The origin of these systematic biases remains controversial. Drawing on data from an extensive array of reaching tasks conducted over the past 30 years, we evaluated the merits of various computational models regarding the origin of motor biases. Contrary to previous theories, we show that motor biases do not arise from systematic errors associated with the sensed hand position during motor planning or from the biomechanical constraints imposed during motor execution. Rather, motor biases are primarily caused by a misalignment between eye-centric and body-centric representations of position. This model can account for motor biases across a wide range of contexts, encompassing movements with the right versus left hand, finger versus hand movements, visible and occluded starting positions, as well as before and after sensorimotor adaptation.

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bioRxiv2023

Ventrointermediate thalamic stimulation improves motor learning in humans

Ventrointermediate thalamic stimulation (VIM-DBS) modulates oscillatory activity in a cortical network including primary motor cortex, premotor cortex, and parietal cortex. Here we show that, beyond the beneficial effects of VIM-DBS on motor execution, this form of invasive stimulation facilitates production of sequential finger movements that follow a fixed sequence but not when the sequence is selected at random. These results highlight the role of thalamo-cortical activity in motor learning.

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bioRxiv2023

A Cerebellar Population Coding Model for Sensorimotor Learning

The cerebellum is crucial for sensorimotor adaptation, using error information to keep the sensorimotor system well-calibrated. Here we introduce a population-coding model to explain how cerebellar-dependent learning is modulated by contextual variation. The model consists of a two-layer network, designed to capture activity in both the cerebellar cortex and deep cerebellar nuclei. A core feature of the model is that within each layer, the processing units are tuned to both movement direction and the direction of movement error. The model captures a large range of contextual effects including interference from prior learning and the influence of error uncertainty and volatility. While these effects have traditionally been taken to indicate meta learning or context-dependent memory within the adaptation system, our results show that they are emergent properties that arise from the population dynamics within the cerebellum. Our results provide a novel framework to understand how the nervous system responds to variable environments.

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bioRxiv2023

Implicit reward-based motor learning

Binary feedback, providing information solely about task success or failure, can be sufficient to drive motor learning. While binary feedback can induce explicit adjustments in movement strategy, it remains unclear if this type of feedback also induce implicit learning. We examined this question in a center-out reaching task by gradually moving an invisible reward zone away from a visual target to a final rotation of 7.5{degrees} or 25{degrees} in a between-group design. Participants received binary feedback, indicating if the movement intersected the reward zone. By the end of the training, both groups modified their reach angle by about 95% of the rotation. We quantified implicit learning by measuring performance in a subsequent no-feedback aftereffect phase, in which participants were told to forgo any adopted movement strategies and reach directly to the visual target. The results showed a small, but robust (2-3{degrees}) aftereffect in both groups, highlighting that binary feedback elicits implicit learning. Notably, for both groups, reaches to two flanking generalization targets were biased in the same direction as the aftereffect. This pattern is at odds with the hypothesis that implicit learning is a form of use-dependent learning. Rather, the results suggest that binary feedback can be sufficient to recalibrate a sensorimotor map.

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bioRxiv2023

Differential Contribution of Sensorimotor Cortex and Subthalamic Nucleus to Unimanual and Bimanual Hand Movements

Why does unilateral subthalamic nucleus deep brain stimulation improve motor function bilaterally? To address this clinical observation, we collected parallel neural recordings from sensorimotor cortex and the subthalamic nucleus during repetitive ipsilateral, contralateral, and bilateral hand movements in patients with Parkinsons disease undergoing subthalamic nucleus deep brain stimulation. We used a cross-validated electrode-wise encoding model to map EMG data to the neural signals. Electrodes in the subthalamic nucleus encoded movement in a comparable manner for both hands during unimanual and bimanual movements, whereas sensorimotor cortex electrodes displayed a strong contralateral bias. To examine representational overlap in encoding across the two hands, we trained the model with data from one condition (contralateral hand) and used the trained weights to predict neural activity for movements produced with the other hand (ipsilateral hand). Overall, between-hand generalization was poor and this limitation was evident in both SMC and STN. A similar method was used to probe representational overlap across different task contexts (unimanual vs. bimanual). Task context was more important for the STN compared to the SMC indicating that neural activity in the STN showed greater divergence between the unimanual and bimanual conditions. These results indicate that whereas SMC activity is strongly lateralized and relatively context-free, STN integrates contextual information with the ongoing behavior. Significance StatementUnilateral subthalamic nucleus deep brain stimulation (DBS) improves both contralateral and ipsilateral motor symptoms of Parkinsons disease. To explore mechanisms for bilateral improvement, parallel neural recordings from the sensorimotor cortex (SMC) and subthalamic nucleus (STN) were recorded in patients with Parkinsons disease undergoing DBS. Neural activity and muscle activity from the hands were collected while patients performed unimanual and bimanual repetitive hand movements. Activity in SMC primarily encoded contralateral movements and was relatively context-free. In contrast, STN encoded movements in a comparable manner for both hands and was sensitive to the behavioral context.

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bioRxiv2023

Perturbation Variability Does Not Influence Implicit Sensorimotor Adaptation

Cerebellar-dependent implicit adaptation has been regarded as a rigid process that automatically operates in response to movement errors in order to keep the sensorimotor system calibrated. This hypothesis has been challenged by recent evidence suggesting flexibility in this learning process. One compelling line of evidence comes from work suggesting that this form of learning is context-dependent, with the rate of learning modulated by error history. Specifically, learning was attenuated in the presence of perturbations exhibiting high variance compared to when the perturbation is fixed. However, these findings are confounded by the fact that the adaptation system corrects for errors of different magnitudes in a non-linear manner, with the adaptive response increasing in a proportional manner to small errors and saturating to large errors. Through simulations, we show that this non-linear motor correction function is sufficient to explain the effect of perturbation variance without referring to an experience-dependent change in error sensitivity. Moreover, by controlling the distribution of errors experienced during training, we provide empirical evidence showing that there is no measurable effect of perturbation variance on implicit adaptation. As such, we argue that the evidence to date remains consistent with the rigidity assumption.

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bioRxiv2023

Predictors of sensorimotor adaption: insights from over 100,000 reaches

Sensorimotor adaptation is essential for keeping our movements well-calibrated in response to changes in the body and environment. For over a century, we have studied sensorimotor adaptation in highly controlled laboratory settings that typically involve small sample sizes. While this approach has proven useful to characterize different learning processes, laboratory studies are typically very underpowered to generate data suited for exploring the myriad of factors that may modulate motor performance. Here, using a citizen science website (testmybrain.org), we collected over 2000 sessions on a visuomotor rotation task. This unique dataset has allowed us to replicate classic motor findings, reconcile controversial findings in the learning and memory literature, and discover novel constraints underlying dissociable implicit and explicit learning processes supporting sensorimotor adaptation. Taken together, this study suggests that large-scale motor learning studies hold enormous potential to advance sensorimotor neuroscience.

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