Biology subjects

Block, H. J.

Publications and source records attributed to Block, H. J..

11 recordsLinked to original sources

bioRxiv2025

The Impact of Different Learning Processes on Acquisition, Transfer, and Proprioception in Complex Motor Tasks

Motor skill learning involves multiple mechanisms, including use-dependent learning (UDL), reinforcement learning (RL), and error-based learning (EBL). These operate over different time scales and neural pathways, contributing uniquely to skill acquisition, consolidation, and transfer. Here we asked how these mechanisms support the acquisition of a spatially complex maze navigation task in five groups of healthy young adults. Groups received one of five types of feedback during training of their unseen dominant hand: UDL (no feedback), RL (binary success/failure feedback with a static threshold), RLA (binary feedback with an adaptive threshold), RLB (binary feedback with adaptive threshold and brief flash of cursor feedback), or EBL (continuous real-time cursor feedback). Skill, transfer, and proprioceptive acuity were assessed pre- and post- training using a speed-accuracy function (SAF) for each hand and a two-alternative forced-choice shape discrimination task. Results showed that UDL and RL groups exhibited no improvement post-training, while EBL, RLA, and RLB groups demonstrated accuracy improvements. EBL and RLB participants experienced a significant reduction in movement variability, with EBL showing a greater decrease compared to UDL. The left-hand SAF revealed improvements in accuracy across all groups except UDL. All groups showed reduced variability in the left hand, suggesting intermanual transfer, with EBL transferring more variability improvements than UDL. No significant proprioceptive changes were observed in any group. These findings provide new insights into motor skill learning, emphasizing that even minimal feedback can facilitate complex skill acquisition and transfer and has significant implications for studies where error-based learning may not be applicable. New and NoteworthyMinimal, adaptive binary feedback can effectively support the acquisition and transfer of spatially complex motor skills. While use-dependent and static reinforcement learning failed to enhance performance, adaptive reinforcement and error-based feedback significantly improved accuracy and reduced movement variability. Notably, these gains transferred to the untrained hand, highlighting the potential of reinforcement-based strategies in contexts where error-based learning is limited or unavailable, offering important implications for rehabilitation and motor training design.

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bioRxiv2025

Frontal and Parietal Contributions to Proprioception and Motor Skill Learning

Motor skill learning is the process of developing new movements with practice until they can be performed automatically. This necessitates the interaction of high-level cognitive processes with low-level sensorimotor mechanisms. Skill learning involves not only changes in the motor system but also proprioception (position sense). Proprioceptive deficits increase variability and decrease accuracy of movement. The somatosensory cortex, where low-level proprioception is processed, is known to play a role in motor skill learning, but the involvement of higher-level proprioceptive regions is unclear. Dorsolateral prefrontal cortex (DLPFC) has been linked to the high-level early stages of motor learning, and indirectly to proprioception. Supramarginal gyrus (SMG), an interface area between motor and sensory cortices, has been linked to higher-order proprioceptive processing. In this study, we asked how activity in DLPFC and SMG influences motor skill learning. Participants learned an upper limb motor skill designed to be spatially complex and dependent on proprioception: tracing a two-dimensional maze as accurately as possible within the desired speed range, using a KINARM Endpoint robotic manipulandum. Proprioceptive acuity (sensitivity and bias) was assessed before and after continuous theta burst transcranial magnetic stimulation (cTBS) was applied to inhibit activity in DLPFC, SMG, or Sham. To measure motor skill, movement accuracy and variability were examined at the trained speed as well as at a faster (more difficult) and a slower (easier) speed. Skill was assessed before and after cTBS, after 40 training trials (early learning) and after another 80 trials (late learning). All three groups showed improvements in movement accuracy and variance, indicating they learned the maze tracing skill. However, the Sham group improved movement variability at the faster speed significantly more than the DLPFC or SMG groups did. This suggests that DLPFC and SMG are important for the more challenging aspects of motor skill learning, consistent with their association with higher-level proprioceptive function.

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bioRxiv2025

Network dynamics for sensory prioritization: Functional connectivity related to individual sensory weighting of vision versus proprioception during upper limb control

Precise control of the hand requires the dynamic integration of visual and proprioceptive (body position sense) sensory cues with internal models, task goals, and motor plans. Individual differences in how visual and proprioceptive cues are weighted have been related to neural substrates, such as posterior parietal regions, yet the underlying neural dynamics are unclear. This study investigated the relationship between visuo-proprioceptive perception during a bimanual pointing task and the whole-brain network dynamics using resting-state functional magnetic resonance imaging (rsfMRI) with both atlas-based and individually-localized ROI seeds. Our results confirm the existence of individual sensory biases, and find they have systematic influences on functional connectivity. Activity between sensorimotor regions and default mode network (DMN) nodes was related to sensory weighting (e.g. individual degree of reliance on vision versus proprioception) and may reflect updating of internal models. The ventral premotor cortex (PMv) emerged as an important node with functional connections suggesting its role for integrating motor plans, internal models, and sensory percepts. Connections from multisensory integration regions like the middle temporal gyrus (MTG) and the superior parietal lobule (SPL), and motor coordination regions in the cerebellum, were related to increased reliance on visual versus proprioceptive information. These findings suggest that individual sensory biases during sensorimotor behavior may be characterized by specific and specialized patterns of neural activity. This research establishes a foundational exploration of the neural systems underlying sensorimotor processing, supporting theories suggesting that learning in either the sensory or motor system may also cause plasticity in the other.

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bioRxiv2024

Somatosensory cortex and body representation: Updating the motor system during a visuo-proprioceptive cue conflict

The brains representation of hand position is critical for voluntary movement. Representation is multisensory, combining visual and proprioceptive cues. When these cues conflict, the brain recalibrates its unimodal estimates, shifting them closer together to compensate. Converging evidence from research in perception, behavior, and neurophysiology suggest that such updates to body representation are communicated to the motor system to keep hand movements accurate. We hypothesized that primary somatosensory cortex (SI) is crucial in this updating process due to its role in proprioception and connections with primary motor cortex. We tested this hypothesis in two experiments. We predicted that proprioceptive, but not visual, recalibration would be associated with change in short latency afferent inhibition (SAI), a measure of sensorimotor integration (influence of sensory input on motor output) (Expt. 1). We further predicted that modulating SI activity with repetitive transcranial magnetic stimulation (TMS) should affect recalibration of the proprioceptive estimate of hand position, but have no effect on the visual estimate or on the normal inverse relationship between proprioceptive and visual recalibration (Expt. 2). Our results are consistent with these predictions, supporting the idea that (1) SI is indeed a key region in facilitating motor system updates based on changes in body representation, and (2) this function is mediated by unisensory (proprioceptive) processing, separate from multisensory visuo-proprioceptive computations. Other aspects of the body representation (visual and multisensory) may be conveyed to the motor system via separate pathways, e.g. from posterior parietal regions to motor cortex. Significance StatementRepresentation of the hand, which is critical for accurate control of movement, comes from weighting and combining available proprioceptive (position sense) and visual cues. Our results suggest that when the hand representation is modified by introducing a conflict between these cues, the motor system receives updates directly from the primary somatosensory cortex (SI). These updates are specific to the change in proprioceptive representation and are absent when cues are not in conflict. This may represent a unisensory pathway to the motor system that conveys information about hand representation, acting in parallel with multisensory pathways involving posterior parietal and premotor regions.

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bioRxiv2024

The role of feedback in responding to gradual and abrupt visuo-proprioceptive cue conflict

When people observe conflicting visual and proprioceptive cues about their static hand position, visuo-proprioceptive recalibration results. Recalibration also occurs during gradual or abrupt visuomotor adaptation, in response to both the cue conflict and sensory prediction errors experienced as the hand reaches to a target. Here we asked whether creating a cue conflict gradually vs. abruptly, or providing error feedback, affects recalibration in a static hand. We examined participants responses to a 70 mm visuo-proprioceptive conflict, imposed by shifting the visual cue forward from the proprioceptive cue (static left hand). Participants pointed with their unseen right hand to indicate perceived bimodal and unimodal cue positions. Conflict was introduced gradually (groups 1 and 2) or abruptly (groups 3 and 4), with performance feedback present (groups 2 and 4) or absent (groups 1 and 3). For abrupt groups, most behavioral change occurred immediately after the conflict began. No-feedback groups (1 and 3) showed comparable magnitudes of overall recalibration, indicating that abrupt and gradual conflicts result in similar recalibration but with different timings. Motor adaptation was evident in the indicator hand with performance feedback (groups 2 and 4). However, performance on a static ruler task suggests proprioceptive recalibration also occurred despite the presence of feedback. Control groups confirmed accurate performance on the pointing task despite the visual cue shift. These findings highlight the distinct timing of recalibration mechanisms for gradual versus abrupt cue conflicts and potential smaller contribution of error mechanisms for a static conflict. New and NoteworthyThe brain may handle spatial conflicts between visual and proprioceptive cues differently for a dynamic hand undergoing visuomotor adaptation than for a static hand. In a static hand, abrupt conflict triggered immediate recalibration without further adjustment, and feedback had little impact on recalibration. This suggests varying roles of multisensory and error mechanisms across motor contexts, underscoring the importance of examining a variety of motor contexts to understand and predict behavior.

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bioRxiv2022

Visuo-proprioceptive recalibration and the sensorimotor map

Spatial perception of our hand is closely linked to our ability to move the hand accurately. We might therefore expect that reach planning would take into account any changes in perceived hand position; in other words, that perception and action relating to the hand should depend on a common sensorimotor map. However, there is evidence to suggest that changes in perceived hand position affect a body representation that functions separately from the body representation used to control movement. Here we examined target-directed reaching before and after participants either did (Mismatch group) or did not (Veridical group) experience a cue conflict known to elicit recalibration in perceived hand position. For the reaching task, participants grasped a robotic manipulandum that positioned their unseen hand for each trial. Participants then briskly moved the handle straight ahead to a visual target, receiving no performance feedback. For the perceptual calibration task, participants estimated the locations of visual, proprioceptive, or combined cues about their unseen hand. The Mismatch group experienced a gradual 70 mm forward mismatch between visual and proprioceptive cues, resulting in forward proprioceptive recalibration. Participants made significantly shorter reaches after this manipulation, consistent with feeling their hand to be further forward than it was, but reaching performance returned to baseline levels after only 10 reaches. The Veridical group, after exposure to veridically-aligned visual and proprioceptive cues about the hand, showed no change in reach distance. These results are not fully consistent with a single common sensorimotor map, but could suggest multiple, interacting body representations. NEW & NOTEWORTHYIf perceived hand position changes, we might assume this affects the sensorimotor map and, in turn, reaches made with that hand. However, there is evidence for separate body representations involved in perception vs. action. After a cross-sensory conflict that results in proprioceptive recalibration in the forward direction, participants made shorter reaches as predicted, but only briefly. This is not fully consistent with a single common sensorimotor map, but could suggest multiple, interacting body representations.

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bioRxiv2022

Retention of visuo-proprioceptive recalibration in estimating hand position

The brain estimates hand position using visual and proprioceptive cues, which are combined to give an integrated multisensory estimate. Spatial mismatches between cues elicit recalibration, a compensatory process where each unimodal estimate is shifted closer to the other. It is unclear how well visuo-proprioceptive recalibration is retained after mismatch exposure. Here we asked whether direct vision and/or active movement of the hand can undo visuo-proprioceptive recalibration, and whether recalibration is still evident 24 hours later. 75 participants performed two blocks of visual, proprioceptive, and combination trials, with no feedback or direct vision of the hand. In Block 1, a 70 mm visuo-proprioceptive mismatch was gradually imposed, and recalibration assessed. Block 2 tested retention. Between blocks, Groups 1-4 rested or made active movements with their directly visible or unseen hand for several minutes. Group 5 had a 24-hour gap between blocks. All five groups recalibrated both vision and proprioception in Block 1, and Groups 1-4 retained most of this recalibration in Block 2. Interestingly, Group 5 showed an offline increase in proprioceptive recalibration, but retained little visual recalibration. Our results suggested that visuo-proprioceptive recalibration is robustly retained in the short-term. In the longer term, contextual factors may affect retention.

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bioRxiv2020

Somatosensory versus cerebellar contributions to proprioceptive changes associated with motor skill learning: A theta burst stimulation study

Background: It is well established that proprioception (position sense) is important for motor control, yet its role in motor learning and associated plasticity is not well understood. We previously demonstrated that motor skill learning is associated with enhanced proprioception and changes in sensorimotor neurophysiology. However, the neural substrates mediating these effects are unclear. Objective: To determine whether suppressing activity in the cerebellum and somatosensory cortex (S1) affects proprioceptive changes associated with motor skill learning. Methods: 54 healthy young adults practiced a skill involving visually-guided 2D reaching movements through an irregular-shaped track using a robotic manipulandum with their right hand. Proprioception was measured using a passive two-alternative choice task before and after motor practice. Continuous theta burst stimulation (cTBS), was delivered over S1 or the cerebellum (CB) at the end of training for two consecutive days. We compared group differences (S1, CB, Sham) in proprioception and motor skill, quantified by a speed-accuracy function, measured on a third consecutive day (retention). Results: As shown previously, the Sham group demonstrated enhanced proprioceptive sensitivity after training and at retention. The S1 group had impaired proprioceptive function at retention through online changes during practice, whereas the CB group demonstrated offline decrements in proprioceptive function. All groups demonstrated motor skill learning, however, the magnitude of learning differed between the CB and Sham groups, consistent with a role for the cerebellum in motor learning. Conclusion: Overall, these findings suggest that the cerebellum and S1 are important for distinct aspects of proprioceptive changes during skill learning.

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bioRxiv2020

The effect of sequence learning on sensorimotor adaptation

Motor skill learning involves both sensorimotor adaptation (calibrating the response to task dynamics and kinematics), and sequence learning (executing the task elements in the correct order at the necessary speed). These processes typically occur together in natural behavior and share much in common, such as working memory demands, development, and possibly neural substrates. However, sensorimotor and sequence learning are usually studied in isolation in research settings, for example as force field adaptation or serial reaction time tasks (SRTT), respectively. It is therefore unclear whether having predictive sequence information during sensorimotor adaptation would facilitate performance, perhaps by improving sensorimotor planning, or if it would impair performance, perhaps by occupying neural resources needed for sensorimotor learning. Here we evaluated adaptation to a distance-dependent force field in two different SRTT contexts: In Experiment 1, 28 subjects reached between 4 targets in a sequenced or random order. In Experiment 2, 40 subjects reached to one target, but 3 force field directions were applied in a sequenced or random order. We did not observe any consistent influence of target position sequence on force field adaptation in Experiment 1. However, sequencing of force field directions facilitated sensorimotor adaptation and retention in Experiment 2. This is inconsistent with the idea that sensorimotor and sequence learning share neural resources in any mutually exclusive fashion. These findings indicate that under certain conditions, perhaps especially when the sequence is related to the sensorimotor perturbation itself as in Experiment 2, sequence learning may interact with sensorimotor learning in a facilitatory manner.

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bioRxiv2020

Visuo-proprioceptive control of the hand in older adults

To control hand movement, we have both vision and proprioception, or position sense. The brain is known to integrate these to reduce variance. Here we ask whether older adults integrate vision and proprioception in a way that minimizes variance as young adults do, and whether older subjects compensate for an imposed visuo-proprioceptive mismatch as young adults do. Ten healthy older adults (mean age 69) and 10 healthy younger adults (mean age 19) participated. Subjects were asked to estimate the position of visual, proprioceptive, and combined targets, with no direct vision of either hand. After a veridical baseline block, a spatial visuo-proprioceptive misalignment was gradually imposed by shifting the visual component forward from the proprioceptive component without the subjects awareness. Older subjects were more variable than young subjects at estimating both visual and proprioceptive target positions (F1,18 = 6.14, p = 0.023). Older subjects tended to rely more heavily on vision than proprioception compared to younger subjects. However, the weighting of vision vs. proprioception was correlated with minimum variance predictions for both older (r = 0.71, p = 0.021) and younger (r = 0.81, p = 0.0047) adults, suggesting that variance-minimizing mechanisms are present to some degree in older adults. Visual and proprioceptive realignment were similar for young and older subjects in the misalignment block, suggesting older subjects are able to realign as much as young subjects. These results suggest that intact multisensory processing in older adults should be explored as a potential means of mitigating degradation in individual sensory systems.

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bioRxiv2019

Increase in weighting of vision vs. proprioception associated with force field adaptation

Hand position can be encoded by vision, via an image on the retina, and proprioception (position sense), via sensors in the joints and muscles. The brain is thought to weight and combine available sensory estimates to form an integrated multisensory estimate of hand position with which to guide movement. Force field adaptation, a form of cerebellum-dependent motor learning in which reaches are systematically adjusted to compensate for a somatosensory perturbation, is associated with both motor and proprioceptive changes. The cerebellum has connections with parietal regions thought to be involved in multisensory integration; however, it is unknown if force adaptation is associated with changes in multisensory perception. One possibility is that force adaptation affects all relevant sensory modalities similarly, such that the brains weighting of vision vs. proprioception is maintained. Alternatively, the somatosensory perturbation might be interpreted as proprioceptive unreliability, resulting in vision being up-weighted relative to proprioception. We assessed visuo-proprioceptive weighting with a perceptual estimation task before and after subjects performed straight-ahead reaches grasping a robotic manipulandum. Each subject performed one session with a clockwise or counter-clockwise velocity-dependent force field, and one session in a null field to control for perceptual changes not specific to force adaptation. Subjects increased their weight of vision vs. proprioception in the force field session relative to the null field session, regardless of force field direction, in the straight-ahead dimension (F1,44 = 5.13, p = 0.029). This suggests that force field adaptation is associated with an increase in the brains weighting of vision vs. proprioception.

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