Signals from tomorrow in sensorimotor control

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48 minutes read

Motor planning relies on predictive mechanisms that allow the nervous system to prepare actions before the corresponding sensory consequences are available. In sensorimotor control, the brain uses internal models to simulate the dynamics of the body and environment, generating expectations about future states of the limb, object, and task context. These internal models enable rapid, feedforward commands that can be executed faster than sensory feedback loops alone would allow, effectively anticipating what will happen rather than waiting to simply react. In everyday behavior, such as catching a ball or typing on a keyboard, the temporal constraints are so tight that successful action is only possible because prediction is embedded into the earliest stages of motor planning.

A central component of these predictive mechanisms is the formation and update of priors in motor planning. Priors reflect learned regularities about how the body behaves and how external forces, objects, and tools respond to movement. When preparing a reach, the nervous system combines current sensory estimates of limb state with prior knowledge about typical target locations, object weights, and recent movement history. As a result, motor commands are biased toward likely outcomes even before any new sensory data can confirm or disconfirm these expectations. This probabilistic integration of priors with sensory evidence aligns with the ā€œbayesian brainā€ hypothesis, according to which the brain represents uncertainty and optimizes behavior by approximating Bayesian inference.

Forward models are often described as the computational substrate of these predictive capabilities. A forward model receives an efference copy of the motor command and generates a prediction of the expected sensory consequences, including proprioceptive, tactile, and visual feedback. This predicted sensory outcome is compared with incoming sensory signals to compute a prediction error. Small errors indicate that the current internal model and motor plan are adequate, whereas large errors signal that the plan must be adjusted or the internal model updated. Because the forward model can generate predictions faster than actual feedback can arrive from the periphery, it allows the system to prepare corrections in advance, effectively compensating for delays inherent in neural transmission and muscle dynamics.

Inverse models complement forward models by mapping desired future states onto the motor commands needed to achieve them. During motor planning, a desired end-effector position, movement trajectory, or force profile is transformed into a pattern of neural activity across motor-related areas that will ultimately produce coordinated muscle activation. Predictive mechanisms ensure that this transformation is not purely kinematic but incorporates the physics of the body, predicted external disturbances, and task-specific constraints. For instance, planning a reach with a heavy object versus a light one engages different predicted muscle forces, even before any contact reveals the true weight. Over repeated experiences, discrepancies between predicted and actual load drive learning, refining both the inverse and forward models to support more accurate planning in future attempts.

From a systems perspective, predictive motor planning involves a distributed network spanning premotor cortex, supplementary motor area, parietal cortex, basal ganglia, cerebellum, and primary motor cortex. Premotor and parietal regions represent action goals, spatial relationships, and contextual information that shape which future states are relevant. The cerebellum is strongly implicated in forward modeling, generating precise temporal predictions of sensory outcomes and contributing to fine-tuned timing of muscle activity. Basal ganglia structures modulate the selection and vigor of planned actions based on predicted reward and cost. Primary motor cortex converts these predictions and decisions into detailed patterns of descending commands, but its output is already shaped by upstream predictive computations rather than being a purely reactive motor relay.

Active inference provides a useful conceptual framework for understanding these predictive mechanisms in motor planning. Under active inference, the brain is viewed as minimizing prediction errors not only by updating sensory beliefs but also by acting on the world to confirm its predictions. In this view, motor commands are generated to make sensory input conform to prior expectations about desired states. Planning an arm movement thus involves forming precise predictions of the desired proprioceptive and visual trajectories and issuing commands that will bring the actual sensory feedback into alignment with these predictions. The resulting action can be seen as the physical realization of an internal hypothesis about how the body should move, continuously refined by prediction error signals.

Predictive mechanisms are especially evident in situations where sensory feedback is unreliable, delayed, or experimentally altered. When visual feedback of the limb is shifted using prisms or virtual reality, participants initially misreach but quickly adapt, indicating that internal models are being recalibrated to new sensorimotor contingencies. During the early stages of adaptation, motor planning relies heavily on priors shaped by previous experience, which can conflict with the altered feedback. As the discrepancy persists, prediction errors drive a gradual change in the planned movement trajectory, ultimately aligning motor commands with the new visual context. Once adaptation is complete, after-effects reveal that motor planning has been fundamentally reconfigured: removing the perturbation causes systematic errors in the opposite direction, reflecting the updated predictive model.

Temporal constraints on movement further reveal the importance of prediction. When rapid corrections are required, such as avoiding an unexpected obstacle during a fast reach, there is insufficient time for full cortical processing of new sensory information. Instead, precomputed predictive contingencies determine how the system will respond to likely perturbations. Motor plans often include flexible ā€œbranchesā€ that can be rapidly engaged depending on which predicted scenario materializes. For example, when reaching toward a target that might jump unpredictably, the initial motor plan encodes a family of potential trajectories, each associated with a prediction about where the target could move. Early in the movement, neural activity in premotor and parietal areas reflects this multiplexed representation of possible futures, collapsing toward a single trajectory as sensory information resolves ambiguity.

Learning and skill acquisition are deeply intertwined with predictive motor planning. As individuals practice a complex movement, such as a tennis serve or skilled musical performance, prediction errors gradually decrease, and motor commands become smoother and more energy-efficient. This optimization depends on improved internal models of limb dynamics, environmental regularities, and task-specific timing. Skilled performers often appear to ā€œmove ahead of time,ā€ adjusting posture and muscle activation fractions of a second before external events occur. These anticipatory adjustments are not reactive but grounded in refined predictive mechanisms that have internalized the temporal and spatial structure of the task. Over time, the computational load during explicit planning diminishes, as predictive control becomes increasingly automatized.

Predictive mechanisms also influence how attention is allocated during motor planning. When an action is prepared, the brain not only predicts the movement trajectory but also the most informative sensory channels and spatial locations. Attentional resources are pre-allocated to expected points of contact, potential sources of perturbation, or critical visual cues. This predictive allocation improves the efficiency of online error correction and minimizes delays in updating the motor plan. For example, prior to grasping a slippery object, both motor commands and sensory gain in the relevant tactile pathways are modulated in anticipation of reduced friction, ensuring that any deviation from the predicted grip state is detected quickly and compensated for in real time.

At the neural population level, predictive motor planning manifests as prospective activity patterns that encode aspects of forthcoming movement before any overt motion occurs. In motor and premotor cortex, neurons often fire in a sequence that mirrors the temporal structure of the impending movement, effectively simulating the action internally. Similarly, cerebellar neurons exhibit firing patterns that correlate with predicted sensory feedback, leading actual feedback by tens of milliseconds. These anticipatory responses are not mere byproducts of preparation; they constitute the generative backbone of sensorimotor control, providing a continuous stream of predictions that shape the trajectory of movement from initiation through execution.

Temporal integration of sensory feedback

Temporal integration of sensory feedback is constrained by the fact that signals from the body and environment arrive with different latencies and noise levels, yet must be combined into a coherent, time-resolved estimate of the current and near-future state. In sensorimotor control, the brain does not simply wait for feedback to arrive and then respond; instead, it continuously fuses incoming information with ongoing predictions generated by internal models. Because proprioceptive feedback from muscles and joints arrives faster than visual information, and tactile signals can be highly transient, the nervous system must assign different temporal weights to each modality. Early after movement onset, proprioception and efference-copy-based estimates tend to dominate; as slower visual information catches up, it is integrated to refine estimates of hand position, object motion, and task-relevant spatial relationships. This dynamic reweighting allows the system to maintain a stable sense of limb state despite varying delays and uncertainties across modalities.

A key problem is that by the time sensory feedback reaches central processing stages, the limb has already moved on. To overcome this, the brain effectively ā€œtime stampsā€ feedback relative to an internal clock and projects it back onto the trajectory it likely originated from. Forward models play a central role here: they generate a running estimate of the limb’s evolving state, which is then corrected as delayed feedback becomes available. For example, visual information about hand position that arrives 100 ms late is not attributed to the current estimated state but to the state that the forward model predicted for that earlier point in time. The system then reconciles these predictions with the delayed measurement, adjusting both the current state estimate and the ongoing motor commands. In this way, temporal integration does not merely sum signals but performs a form of retrospective inference over the recent past to keep perception and action aligned.

Experimental perturbations highlight how temporal integration is tuned to both delay and reliability. When visual feedback of a moving limb is artificially delayed, individuals initially experience a mismatch between predicted and observed positions, often reporting that the visual cursor ā€œlags behindā€ the felt hand. Over repeated exposure, the nervous system partially compensates by altering how it integrates visual and proprioceptive information over time. The influence of delayed vision on online corrections is reduced, and greater weight is given to proprioceptive and predictive estimates. If the delay is modest and consistent, internal models adapt so that the predicted visual consequences of movement are shifted in time, effectively learning a new mapping from motor commands to temporally offset feedback. Temporal integration thus reflects not only fixed neural conduction delays but also learned priors about when sensory consequences are expected to occur.

The process of temporal integration can be framed within the bayesian brain hypothesis. At each moment, the nervous system maintains a probabilistic estimate of the current and near-future state, incorporating both priors and newly arriving evidence. Priors encode expectations about limb dynamics, environmental stability, and typical feedback latencies. Sensory signals, arriving with modality-specific delays and noise, provide likelihoods that update these priors. Importantly, these likelihoods are themselves time-indexed: the brain estimates not only what the sensory signal indicates about position or velocity but also when that information is valid. The resulting posterior distribution over states is then used to guide immediate motor corrections and to update the predictions that will structure subsequent integration. Temporal integration is therefore an ongoing Bayesian inference process over both state and time.

Within this framework, prediction errors are computed in a temporally specific manner. Rather than a single global mismatch, the system compares predicted and observed sensory consequences at multiple time scales. Fast loops, involving spinal and brainstem circuits, integrate recent proprioceptive and cutaneous input over tens of milliseconds, supporting rapid reflex-like adjustments. Intermediate loops, engaging cerebellar and cortical circuits, integrate feedback over hundreds of milliseconds to refine ongoing trajectories and adapt muscle synergies. Slower loops, spanning seconds to minutes, integrate performance outcomes, such as task success or failure, to recalibrate internal models and longer-term priors. Each loop operates with its own temporal window and sensitivity, but all are nested within a common predictive architecture that aligns feedback with expectations at the appropriate delay.

Temporal integration is especially evident during rapid online corrections of movement trajectories. When a target jumps to a new location mid-reach, visual information about the jump is subject to significant processing delays, yet corrective adjustments can begin within 100–150 ms. Behavioral and neurophysiological data suggest that the nervous system maintains a temporally extended representation of both the original and possible future target states, continuously updating predicted trajectories. As soon as visual evidence confirms a target displacement, this information is integrated with the already unfolding motor plan, effectively splicing a new predicted trajectory into the ongoing movement. The correction does not start from scratch; it is grounded in a temporally integrated estimate that combines past efference copies, proprioceptive feedback, and the newly updated visual estimate of target position.

Multisensory integration across time further complicates the picture. For many tasks, such as object manipulation, relevant information is distributed across modalities and time points: early contact forces provide clues about object weight, later slip signals reveal surface friction, and ongoing visual feedback informs about object trajectory. The nervous system must integrate these temporally staggered cues into a unified estimate that governs grip force, wrist orientation, and arm posture. Studies of grip-force control show that people adjust forces not simply in response to instantaneous slip but based on the temporal pattern of tactile input, combining recent history with predictions about how forces will evolve. The result is a form of temporal filtering, where transient fluctuations are discounted if inconsistent with predicted object properties, whereas persistent deviations drive meaningful corrections.

Active inference offers a useful lens on these processes. Under active inference, the brain is continuously minimizing prediction errors by updating beliefs and by acting on the world to bring sensory input into line with those beliefs. Temporal integration of sensory feedback is then the process by which temporally distributed evidence is accumulated to revise predictions about how the body is moving and how it should move next. Rather than passively recording a sequence of sensory snapshots, the system uses a temporally deep generative model that links past, present, and anticipated future states. Incoming feedback is compared to predicted sensory trajectories, not just to point estimates, so that persistent mismatches over time are more informative than isolated discrepancies. This temporal smoothing reduces the impact of momentary noise while preserving sensitivity to systematic changes in the environment or the body.

Crucially, temporal integration interacts with attention and task demands. When a task emphasizes rapid corrections, such as intercepting a moving object, the nervous system prefers shorter integration windows that prioritize recent sensory information and fast predictions at the expense of stability. In contrast, tasks requiring precision and stability, such as maintaining a delicate posture or performing fine surgical manipulations, recruit longer integration windows that average over more evidence, yielding smoother but slower corrections. The brain can flexibly adjust these temporal windows based on contextual cues, expected perturbation statistics, and internal arousal or vigilance levels. This flexibility ensures that temporal integration remains tuned to the demands of ongoing behavior rather than being fixed by hardwired delays alone.

At the neurophysiological level, temporal integration of sensory feedback is implemented through synaptic, circuit, and network dynamics that endow neural populations with memory for recent input. Recurrent connectivity in sensorimotor cortices allows activity patterns to persist beyond the immediate arrival of a sensory signal, effectively storing a short history of limb state estimates. In the cerebellum, parallel fiber and Purkinje cell dynamics support finely tuned temporal kernels, enabling the system to learn precise timing relationships between motor commands and resulting sensory feedback. Subcortical structures, including the basal ganglia and thalamus, contribute additional temporal filtering and gating, controlling when and how feedback influences downstream motor structures. Together, these mechanisms allow neural circuits to blend prediction and feedback into continuous, temporally coherent control signals.

Temporal integration also underpins the sense of agency and ownership over movement. When sensory feedback arrives at the appropriate time and matches predicted consequences, actions feel self-generated and under voluntary control. If feedback is delayed, temporally inconsistent, or statistically improbable given ongoing predictions, the sense of agency can be disrupted. Experiments that introduce artificial temporal offsets between motor actions and visual or tactile feedback demonstrate that even modest delays can alter perceived authorship, especially when delays vary unpredictably. These findings underscore that the nervous system is not merely sensitive to the spatial content of feedback but also to its temporal alignment with internal predictions. Agency thus emerges from successful temporal integration of predicted and actual sensory events.

Over learning and development, the temporal integration of sensory feedback becomes increasingly optimized for the specific dynamics of the body and environment. Infants initially display coarse temporal coupling between action and sensation, with wide integration windows and relatively imprecise predictions. Through repeated experience, they acquire more accurate internal models of feedback delays and limb dynamics, sharpening the temporal precision of integration. Skilled adults exhibit highly tuned temporal weighting, quickly discounting feedback that is inconsistent in timing or reliability with established priors about body-environment interactions. This tuning remains plastic throughout life, as evidenced by adaptation to new tools, altered sensory delays in virtual environments, or changes following injury. Temporal integration is therefore not a fixed property of the nervous system but a learned, context-sensitive strategy that continually recalibrates how feedback is used to shape ongoing and future movement.

Neural encoding of future movement states

Encoding of future movement states is distributed across multiple levels of the neuraxis, with neural populations representing not only current kinematics and muscle activity but also trajectories and outcomes that have yet to unfold. In sensorimotor control, this prospective coding emerges as structured patterns of activity that precede and predict upcoming states of the limb, effector, or task environment. Rather than passively reflecting the immediate motor command, cortical and subcortical circuits instantiate a temporally deep representation that spans from the recent past into the near future, enabling rapid, context-sensitive adjustments when conditions change. This temporally extended encoding supports the brain’s ability to behave as if it had access to ā€œsignals from tomorrow,ā€ anticipating the consequences of ongoing actions before peripheral feedback becomes available.

In motor and premotor cortex, future movement states are reflected in preparatory activity that unfolds hundreds of milliseconds before movement onset. Single neurons and neural populations show tuning to upcoming direction, amplitude, speed, and even muscle synergies, often in a manner that is more predictive of the impending action than of any current behavior. During the delay period of instructed-delay tasks, for example, population activity settles into distinct preparatory states that correlate with the planned reach direction or grasp configuration. These preparatory states occupy low-dimensional manifolds in neural state space, such that different intended movements correspond to different trajectories through this manifold. When the ā€œgoā€ cue arrives, the system transitions smoothly from these preparatory configurations into dynamical regimes that drive muscle activation, indicating that future movement states were already encoded in the geometry of ongoing neural activity.

Neural trajectories in population space provide a powerful way to quantify this prospective encoding. Using dimensionality reduction techniques such as principal component analysis or latent dynamical systems models, researchers have shown that motor cortical activity during movement can be captured as a set of trajectories that begin well before motion and continue throughout execution. Importantly, the initial segment of these trajectories encodes the expected evolution of limb state, including intermediate positions and velocities, not just the endpoint. This suggests that neural populations implement internal dynamics that generate entire movement sequences as predictive patterns, rather than issuing commands moment by moment in a strictly reactive fashion. Deviations from these expected trajectories, induced by unexpected perturbations, appear as structured departures in neural state space that correlate with online corrections.

Parietal and premotor regions contribute to encoding future states by combining sensory information, task rules, and priors about likely outcomes into abstract representations of upcoming actions. In posterior parietal cortex, neurons represent intended reach targets, future hand positions in eye-centered or body-centered coordinates, and anticipated visual consequences of movement. Activity in these regions can predict not only where the hand will go but also how the visual scene is expected to change as a result. Premotor areas, especially dorsal premotor cortex, encode conditional action plans that depend on future sensory contingencies, such as whether a target will appear, move, or change color. During ambiguous or probabilistic tasks, neural ensembles simultaneously represent multiple potential future states, with the strength of each representation reflecting its subjective probability. As sensory evidence accumulates, these competing encodings evolve, with one trajectory ultimately dominating as the chosen future state.

The cerebellum plays a central role in encoding predicted future sensory states associated with ongoing motor commands. Purkinje cells and deep cerebellar nuclei exhibit firing patterns that lead actual movement and sensory feedback by tens of milliseconds, consistent with forward-model computations that map efference copies of motor commands onto anticipated proprioceptive and exteroceptive signals. These predictive patterns are temporally precise: shifts in the timing of motor output or feedback produce corresponding adjustments in cerebellar activity. This temporal lead allows cerebellar circuits to issue corrective signals to brainstem and cortical targets before substantial errors accumulate, effectively encoding a near-future snapshot of the controlled limb and environmental interaction. The cerebellum’s microcircuitry, with its parallel fibers and time-sensitive synaptic dynamics, is well suited for learning and maintaining these temporally offset representations.

Basal ganglia circuits contribute a complementary form of future-state encoding focused on action value, vigor, and outcome likelihood. Neurons in the striatum and dopaminergic midbrain encode predictions about future rewards, costs, and task success associated with ongoing and planned movements. These predictions influence which motor plans are selected and how forcefully they are executed, shaping the trajectory of behavior over time. Phasic dopamine signals report prediction errors between expected and obtained outcomes, updating the internal value landscape that informs future choices. In this way, basal ganglia networks embed predictions about the long-term consequences of action sequences into the evolving sensorimotor state, biasing neural trajectories in motor and premotor cortex toward more advantageous futures.

At the level of single neurons, future-state encoding often appears as anticipatory modulation of firing rates or spike timing. In primary motor cortex, many neurons begin changing their activity before any measurable muscle activity or limb displacement, with tuning curves aligned more closely to forthcoming than to ongoing kinematics. Some neurons encode predicted load forces or interaction torques that will arise later in the movement, particularly during tool use or object manipulation. In parietal and premotor areas, anticipatory activity can represent future contact points, upcoming grip configurations, or anticipated perturbations, even when the precise timing of these events is uncertain. These anticipatory patterns reflect the integration of internal models with contextual cues, allowing neurons to represent not only ā€œwhat isā€ but ā€œwhat is about to be.ā€

Neural oscillations provide another substrate for encoding future movement states. Beta-band activity (approximately 13–30 Hz) in sensorimotor cortex and basal ganglia is closely linked to the maintenance of the current motor set and the suppression of premature movements, whereas its desynchronization heralds the initiation of new actions. The timing of beta suppression and rebound can predict when a movement will occur and how it will unfold, effectively marking transitions between current and future motor states. Gamma and higher-frequency oscillations have been implicated in binding distributed neural assemblies that encode different aspects of the forthcoming movement, such as target location, effector selection, and expected sensory consequences. Phase relationships between oscillatory populations may coordinate the sequential activation of subcircuits encoding successive future states, providing a temporal scaffold for unfolding actions.

Within frameworks such as the bayesian brain and active inference, neural encoding of future states is interpreted as the implementation of generative models that predict how hidden causes (like joint torques and external forces) will produce sensory data over time. Under these views, neural activity does not merely reflect current sensory evidence; it represents beliefs about latent variables and their future trajectories. Prospective neural signals then correspond to predictions produced by these generative models, whereas feedback-related activity corresponds to updating these beliefs when prediction errors arise. For example, predicted proprioceptive trajectories are encoded in motor and somatosensory cortices, while predicted visual trajectories are encoded in parietal and occipital areas; actions are generated partly to fulfill these predictions by bringing actual sensory input into alignment with them.

Encoding of multiple possible futures is particularly evident in tasks involving decision-making under uncertainty. When an animal or human must choose between two movement options, population recordings in dorsal premotor and parietal cortex reveal concurrent representations of the alternative actions before a final decision is made. Neural trajectories momentarily branch toward different future states, with relative trajectory strength influenced by prior probabilities, reward expectations, and recent history. As disambiguating cues appear, activity converges toward a single branch, indicating commitment to a particular future. This branching dynamics implements a form of probabilistic motor planning, in which the nervous system preserves flexibility by maintaining encoded representations of several potential futures until sufficient evidence accumulates.

Sensorimotor adaptation provides a clear window into how neural encoding of future states is updated with experience. During visuomotor rotations or force-field perturbations, initial movements reflect future states predicted by previously learned internal models, which are now incorrect. Neural activity in premotor, motor, and cerebellar areas initially encodes these outdated predictions, resulting in systematic errors. As prediction errors accumulate, synaptic plasticity reshapes the internal models, altering the neural trajectories that represent future states. Over time, preparatory and movement-related activity evolve to predict the new sensorimotor contingencies, leading to accurate movements despite altered feedback. When the perturbation is removed, after-effects indicate that future states are still encoded according to the adapted internal model, until further experience recalibrates the system.

The encoding of future states is closely linked to efference copy signals and corollary discharge pathways, which convey information about outgoing motor commands to sensory and associative areas. These internal copies enable downstream regions to generate predictions about upcoming sensory input, predicting, for instance, the reafferent consequences of self-generated movement. In visual and somatosensory cortices, neural responses to self-produced stimuli are attenuated or shifted in time, reflecting subtraction or alignment of predicted input. This predictive modulation relies on encoded future states of the body and environment, ensuring that sensory processing focuses on unexpected or externally generated events rather than those that can be forecast from internal motor commands.

Temporal precision is a critical feature of future-state encoding. For the nervous system to compensate effectively for transmission delays and muscle dynamics, predictions must be appropriately time-locked to the evolution of movement and feedback. In many experiments, neural activity that predicts a particular kinematic variable (like hand velocity) is temporally advanced relative to the actual movement, with an optimal lead time that depends on the recording site and behavioral context. Cerebellar and frontal areas typically show stronger and earlier predictive encoding, whereas primary sensory areas are more closely tied to actual feedback. This temporal gradient of prediction allows upstream structures to shape downstream processing so that by the time feedback arrives, the relevant circuits have already been biased toward expected states.

Encoding of future movement states extends beyond single actions to encompass longer-term sequences and routines. In tasks involving stereotyped action chains, such as grooming sequences in rodents or well-practiced piano passages in humans, neural ensembles in motor, premotor, and supplementary motor areas exhibit activity patterns that foreshadow upcoming elements of the sequence several steps ahead. These prospective signals reflect chunked representations, where a complex sequence is encoded as a structured series of future states rather than as independent, isolated movements. The system can then smoothly transition between elements with minimal deliberation, as upcoming states are already partially activated before the current element is completed. Disruption of these prospective encodings, through lesions or transient inactivation, leads to fragmentation and dysfluency of sequential behavior.

Future-state encoding is also modulated by attention, motivation, and task context. When an individual expects a perturbation, such as a sudden force pulse or target jump, neural populations allocate representational resources to potential corrective states even before any change occurs. This manifests as low-amplitude, latent activity patterns in motor-related areas that correspond to candidate compensatory movements. If the perturbation actually happens, these latent representations are rapidly amplified and expressed as overt corrections. When no perturbation occurs, they remain subthreshold, never reaching full motor implementation. This ā€œready-to-launchā€ encoding of contingency-specific futures supports rapid, context-appropriate responses without incurring the metabolic cost or behavioral consequences of prematurely executing the corrective action.

At the level of neural coding strategies, future states are encoded through a combination of rate codes, temporal codes, and population-level dynamics. Some neurons increase or decrease their firing rates to reflect expected movement parameters or sensory events, while others shift the timing of spikes relative to ongoing oscillations to encode additional predictive information. Population codes distribute predictions across many neurons, such that any single unit may contribute only weakly but the ensemble as a whole robustly specifies future trajectories. This redundancy and distributed representation confer resilience to noise and local perturbations: even if some neurons fail or misfire, the encoded future state can still be read out with sufficient accuracy to guide behavior.

Neural encoding of future states has practical implications for brain-machine interfaces (BMIs) and neuroprosthetic control. Because cortical and subcortical populations contain information about intended movements before execution, decoders can leverage these anticipatory signals to improve responsiveness and stability. For instance, decoding algorithms that estimate the near-future state of a prosthetic limb, rather than the instantaneous state alone, can generate smoother and more predictive control signals, better compensating for delays in actuation and feedback. Similarly, incorporating probabilistic models that mirror the brain’s own predictive coding—integrating priors with moment-to-moment neural activity—can help BMIs infer the most likely future trajectory the user intends, even when neural signals are noisy or partially missing. This alignment between artificial decoders and biological encoding of future states promises more naturalistic and robust neuroprosthetic performance.

Taken together, evidence from single-neuron recordings, population analyses, and computational modeling converges on the view that neural systems instantiate rich, temporally extended encodings that reach ahead into the future. These encodings are not static predictions but dynamically evolving hypotheses about how motor commands, body dynamics, and environmental interactions will unfold over multiple time scales. Their continual refinement through prediction errors and learning underpins the flexibility and adaptability of motor behavior, allowing sensorimotor control to operate as if guided by information that has not yet arrived at the sensory periphery.

Computational models of anticipatory control

Computational models of anticipatory control seek to formalize how the nervous system generates and refines predictions about future states in the service of efficient action. Many such models treat sensorimotor control as an inference problem, where the brain must estimate both the current and near-future state of the body and environment from noisy, delayed sensory data and internal signals. Under this view, anticipatory adjustments are not ad hoc reflexes but the output of a system that continuously solves probabilistic state-estimation and control problems subject to temporal constraints. These models provide a principled language for linking neural dynamics, behavior, and learning, and they help clarify how ā€œsignals from tomorrowā€ emerge from mechanisms that are forward-looking but mechanistically grounded.

State-space models form a foundational framework for describing anticipatory control. In these models, the state of the system includes kinematic variables such as position and velocity, as well as internal variables like muscle activation and latent forces. The evolution of this state is specified by dynamical equations that incorporate inertial, muscular, and environmental properties. Anticipation enters through predictive propagation of the current state into the future: given a motor command, the model forecasts where the limb will be a short time later, even before new sensory feedback arrives. Stochastic variants of these models treat process and measurement noise explicitly, allowing them to capture variability in both motor output and sensory signals. This probabilistic treatment is crucial for understanding how the system can remain stable and accurate despite uncertainty and delay.

Model-based control that relies on internal forward and inverse models has been particularly influential. Forward models predict the sensory consequences of motor commands, while inverse models compute the commands needed to achieve desired future states. Computational approaches such as optimal feedback control (OFC) embed these components within a unified framework, in which the controller selects motor commands to minimize a cost function over time. The cost function typically penalizes deviations from task goals, excessive effort, and variability, implicitly shaping anticipatory strategies. Because OFC is inherently predictive—choosing actions based on their expected future consequences—it naturally generates feedforward components like anticipatory postural adjustments and predictive grip-force modulation, as well as flexible feedback responses when perturbations occur.

In OFC and related formulations, anticipatory control emerges from the interplay between prediction and feedback. The controller uses a forward model to simulate how different candidate commands will influence future states and associated costs, and then selects the command that minimizes the expected cumulative cost. This computation yields motor commands that are tuned not only to immediate demands but also to forthcoming phases of the movement. For example, when lifting an object, the optimal policy predicts the forces needed to prevent slip and tailors grip and load forces in advance, with only minor corrections later. Importantly, the same policy can generate different anticipatory behaviors when task parameters or priors change—for instance, when the object’s weight distribution becomes more uncertain, the model predicts more conservative grip strategies.

Kalman filtering and its nonlinear extensions provide a mathematically precise account of how predictions and sensory feedback are integrated over time. In linear-Gaussian settings, the Kalman filter propagates a state estimate forward using a dynamical model, then corrects it using delayed, noisy sensory measurements. The amount of correction depends on the relative uncertainty of prediction and measurement, captured by the Kalman gain. In sensorimotor control, this framework explains how the brain can rely more heavily on efference-copy-based predictions when sensory feedback is unreliable or delayed, and shift toward feedback when it becomes more precise. Anticipatory behavior arises because the filter’s prediction step generates a best estimate of near-future states before new observations arrive, allowing control policies to act on these forecasts rather than on stale feedback alone.

Nonlinear and hierarchical extensions of these estimation schemes, such as unscented Kalman filters and particle filters, have been used to model more complex motor behaviors. These methods can represent multimodal distributions over possible future states, making them well suited for situations with ambiguous or multi-stable outcomes. For example, during movement planning under uncertainty about target location, a particle filter can maintain a set of hypotheses about where the target might be and how the limb should move in each case. Control policies can then be designed to steer the limb along trajectories that remain flexible enough to accommodate multiple possible futures, with anticipatory adjustments biased toward the most probable hypotheses as new information arrives.

Computational models inspired by the bayesian brain hypothesis frame anticipatory control as approximate Bayesian inference over latent states and parameters. Within this perspective, internal models encode priors about body dynamics, environmental regularities, and feedback delays. Motor commands are selected to maximize expected performance under these priors, updated continuously by prediction errors derived from sensory feedback. Anticipatory control reflects the influence of these learned priors: when certain outcome patterns have been experienced repeatedly, the system begins to act as if those outcomes are already partially known, adjusting posture, muscle co-contraction, and sensorimotor gains in advance. Variability in anticipatory behavior across individuals and contexts is thus interpreted as differences in underlying priors and in the efficiency of inference mechanisms.

Active inference generalizes this Bayesian view by placing prediction-error minimization at the center of both perception and action. In active inference models, the organism is endowed with a generative model that predicts how hidden causes—such as joint torques, external forces, or object dynamics—will produce sensory input over time. The system maintains beliefs about current and future states and acts so as to make incoming sensory data conform to its preferred predictions. Anticipatory postural adjustments, for instance, are interpreted as actions that preemptively reduce expected prediction errors associated with impending disturbances, such as a self-initiated arm raise or an anticipated shove. Rather than computing control signals in a separate module, the system performs gradient descent on a free-energy functional, in which anticipatory actions help maintain low prediction error trajectories.

Within active inference, temporal depth of the generative model is crucial. The model specifies not just the current mapping from hidden states to sensations but also the expected evolution of those states and sensations over time. This temporal hierarchy allows the system to represent and select among entire future trajectories. Higher levels encode slower, more abstract predictions (such as task goals and action sequences), while lower levels encode fast, detailed kinematics and muscle activations. Anticipatory control emerges as lower levels attempt to realize predictions issued from higher-level policies, with both prediction and action unfolding over multiple time scales. Perturbations generate prediction errors that propagate up and down the hierarchy, refining both long-term plans and moment-to-moment motor commands.

Reinforcement learning (RL) offers another important computational framework for anticipatory control, particularly regarding how predictions about future reward, cost, and success shape motor planning. In RL-based models, an agent learns a policy that maps states to actions by maximizing expected cumulative reward. Anticipatory elements arise because the value function estimates the long-term consequences of current actions, biasing behavior toward options that yield better future outcomes. For motor tasks, this means that the agent learns not only how to reach a target but also how to structure movement onset, trajectory, and force profiles to optimize accuracy, energy expenditure, and safety. Internal prediction of value—encoded, for instance, by dopaminergic signals—guides the selection and vigor of motor commands before their consequences are realized.

Model-based RL explicitly incorporates internal models of dynamics into the learning process. Rather than learning policies solely from trial-and-error experience, the agent uses a learned forward model to simulate potential futures offline, evaluating hypothetical action sequences without physically executing them. This enables anticipatory strategies that are more sample efficient and flexible than those of purely model-free agents. In the biological setting, such planning-like computations could be implemented by neural circuits that replay or preplay state trajectories, as observed in hippocampal and cortical activity. Anticipatory muscle synergies, posture adjustments, and trajectory planning can be understood as manifestations of policies that have been refined through internal simulations of ā€œwhat will happen if I move this wayā€ before actual execution.

Computational models based on optimal control theory clarify how anticipatory control balances accuracy with efficiency and robustness. Linear quadratic Gaussian (LQG) control, for example, combines linear-quadratic regulators with Kalman filtering to generate control laws that are mathematically optimal under assumptions of linearity and Gaussian noise. In these models, anticipatory components emerge as part of the optimal policy, not as separate add-ons: the controller naturally applies feedforward torques that counteract predictable disturbances, such as gravity or centripetal forces, while retaining feedback gains that correct for unpredicted perturbations. This blending of predictive and reactive elements mirrors observed human motor behavior, where movements appear both proactive and responsive depending on context.

Computational approaches have also emphasized the role of internal models of environmental dynamics in anticipatory control. In tasks involving interaction with objects, the system must predict how external bodies will move in response to applied forces, friction, and contact geometry. Models incorporating object-centric state variables—mass, inertia, elasticity—demonstrate that anticipatory strategies like timing grip forces to a swinging object or pre-shaping the hand for expected contact can be derived from learned dynamical representations. When these models are exposed to new tools or altered dynamics, they exhibit adaptation trajectories similar to those seen in human participants: initial prediction errors drive rapid adjustments in both forward and inverse models, leading to updated anticipatory commands that better match the new task demands.

Another class of models, dynamical systems approaches, focuses on how neural populations implement anticipatory control through intrinsic dynamics rather than explicit error-correction rules. In these models, neural activity evolves along trajectories in a high-dimensional state space, shaped by recurrent connectivity and external inputs. Movement preparation corresponds to steering the system into an appropriate initial condition from which the intrinsic dynamics will generate the desired trajectory. Anticipatory behavior is encoded in the structure of these dynamics: initial states and attractor basins are configured so that, in the absence of perturbations, the system flows along a path that produces the intended sequence of motor states. Perturbations displace the system, but carefully tuned dynamics can guide it back toward the desired trajectory, effectively implementing robust, predictive control without continuous recomputation of optimal commands.

Dynamical systems models can also capture the encoding of multiple potential futures. When the network is set up with multiple attractors corresponding to different actions, preparatory activity may place it near a decision boundary, allowing rapid convergence to one or another attractor when disambiguating cues arrive. This configuration inherently supports anticipatory readiness: the system is already positioned so that minimal additional input is required to commit to a chosen future state. Such models provide a mechanistic account of how populations in premotor and parietal cortex can represent competing action plans in parallel and then quickly resolve them into a single motor command when conditions clarify.

Computational work has further explored how learning shapes anticipatory control over developmental and practice time scales. Error-based learning rules, such as gradient descent on prediction error or cost, allow internal models and control policies to be gradually refined. Experience in a stable environment encourages the formation of strong priors that support accurate prediction and efficient planning, while exposure to variable or volatile conditions yields more cautious, low-gain anticipatory strategies that remain flexible. Meta-learning models extend this idea by allowing the system to learn how quickly it should adjust its internal models in response to errors, thereby tuning its own adaptation rate. This helps explain why some individuals or skills adapt rapidly to perturbations while others remain more rigid: their meta-parameters governing learning and confidence in priors differ.

Crucially, computational models have been used to test hypotheses about the neural implementation of anticipatory control. By fitting model parameters to behavioral data and neural recordings, researchers can infer which cost functions, internal models, and learning rules most plausibly underlie observed behavior. For example, fitting OFC models to reaching trajectories under different perturbations has revealed that humans often trade off effort and variability in a way that closely matches quadratic cost assumptions. Similarly, active inference models fitted to eye movement and posture data suggest that the brain may represent beliefs about future states in a hierarchical, temporally deep format. These modeling efforts bridge the gap between abstract theories of prediction and concrete neural and behavioral measurements.

Computational perspectives also highlight limitations and boundary conditions of anticipatory control. Models show that when delays become too long or noise too high, predictive strategies can overshoot or destabilize the system, leading to oscillations or maladaptive anticipatory responses. This helps illuminate why certain neurological conditions, which alter conduction delays, noise levels, or internal model fidelity, produce characteristic motor symptoms such as tremor, rigidity, or dysmetria. In these cases, the parameters that normally allow predictive mechanisms to offset modest delays and uncertainty are pushed beyond a critical threshold, so that anticipatory control becomes a liability rather than an asset.

Computational models serve as a design blueprint for artificial systems that aim to emulate biological anticipatory control. Robotics and prosthetics increasingly rely on internal models, predictive state estimation, and optimal control to generate movements that are smooth, robust, and responsive to perturbations. By integrating principles from OFC, active inference, and RL, engineers construct controllers that adjust feedforward and feedback components based on learned models of body and environment, much as the nervous system appears to do. These efforts not only validate the relevance of computational theories to real-world control problems but also provide a testbed for exploring how different predictive architectures perform under conditions that are difficult to replicate in biological experiments.

Implications for rehabilitation and neuroprosthetics

Translating insights about anticipatory mechanisms into clinical practice reshapes how rehabilitation is conceptualized and delivered. Traditional approaches frequently emphasize corrective, feedback-driven exercises that respond to movement errors after they occur. In contrast, evidence from sensorimotor control research indicates that many motor impairments arise from disrupted prediction, faulty internal models, or maladaptive priors rather than from weakness or loss of reflexes alone. Rehabilitation strategies that explicitly target predictive processes—helping patients relearn how to forecast the consequences of their actions and to integrate delayed, noisy feedback—are therefore poised to improve outcomes beyond what is achievable with purely reactive training.

One major implication is the need to distinguish between deficits in execution and deficits in prediction. After stroke, traumatic brain injury, or neurodegenerative disease, patients may retain sufficient muscle strength to produce movements, yet their motor planning is compromised because internal models no longer accurately map motor commands to future states. Clinically, this can manifest as overshooting, undershooting, or clumsy timing, particularly when tasks demand rapid adjustments or involve unpredictable perturbations. Assessment protocols that probe anticipatory components—such as feedforward postural adjustments, predictive grip-force scaling, or adaptation to altered visual feedback—can reveal hidden impairments in internal modeling that might be missed by standard strength or range-of-motion tests.

Rehabilitation programs that focus on recalibrating internal models treat prediction errors as an engine for recovery. Task-specific training with well-controlled perturbations, such as visuomotor rotations, force fields, or delayed visual feedback, can be used to drive plasticity in forward and inverse models. By gradually varying the magnitude, direction, and timing of perturbations, therapists can shape how patients update their priors about limb dynamics and environmental forces. Success depends on providing predictable patterns of disturbance initially, allowing patients to infer reliable rules, and only later introducing variability to promote generalization. The objective is not simply to correct each movement, but to rebuild the generative models that govern future behavior.

The cerebellum’s central role in predictive control makes cerebellar disorders particularly relevant for these approaches. Patients with cerebellar ataxia often display profound deficits in learning from sensory prediction errors, leading to persistent inaccuracies even with extensive practice. Rehabilitation for such patients may benefit from shifting emphasis away from error-based adaptation toward strategies that exploit explicit instruction, compensatory visual guidance, or altered task structures that reduce reliance on precise forward modeling. Training protocols can be designed to provide richer, more immediate feedback to circumvent impaired prediction—such as augmented visual or haptic cues that stabilize performance despite faulty internal models—while still engaging whatever residual adaptive capacity remains.

Disorders of the basal ganglia, notably Parkinson’s disease, alter how the nervous system encodes the future value and vigor of actions. Patients may have intact kinematics under externally cued conditions yet show bradykinesia, freezing, or difficulty initiating self-generated movements. From a predictive perspective, dopamine depletion degrades internal estimates of expected reward and success, biasing the system toward conservative, low-vigor policies. Rehabilitation strategies that enhance external structure—using rhythmic auditory cues, visual markers, or task schedules—partially substitute for impaired internal prediction by making relevant future states more explicit. Training can also emphasize building new priors about safe, high-vigor movement through repeated success in structured contexts, gradually reducing reliance on external cues as confidence and predictive stability increase.

In spasticity and dystonia, aberrant anticipatory activation patterns and maladaptive synergies often reflect internal models that have been shaped by years of moving within pathological constraints. Simply stretching or strengthening muscles may not suffice; therapy must target the internal representations that cause inappropriate co-contraction or poorly timed activation. Protocols that encourage exploration of novel movement patterns in a safe, guided environment can expose the nervous system to alternative sensorimotor contingencies. By systematically varying load, support, and speed, therapists can present situations where maladaptive predictions fail and more efficient strategies are rewarded, gradually shifting priors toward healthier coordination.

Postural control provides a clear domain in which predictive mechanisms are crucial for maintaining stability. Anticipatory postural adjustments—subtle shifts in center of mass and muscle activation that occur before voluntary movement or external disturbance—are often diminished after neurological injury or with aging. Interventions that train patients to anticipate predictable perturbations, such as platform translations or self-initiated arm raises while standing, can strengthen these feedforward components. Combining repeated exposure to predictable disturbances with variable timing and direction encourages the system to form robust internal models of body dynamics, improving stability not merely by strengthening muscles but by optimizing when and how they are activated.

Active inference offers a conceptual framework for rethinking therapeutic goals. Under this view, patients attempt to minimize prediction errors by revising their beliefs about what movements are possible and by acting in ways that confirm those beliefs. After injury, if early attempts at movement repeatedly fail or generate pain, patients may implicitly adopt new priors that favor immobility, guarded postures, or low-effort strategies. These priors then bias future motor planning toward restricted motion, reinforcing disability. Rehabilitation that explicitly engineers successful, low-pain experiences can counteract these maladaptive beliefs. By structuring tasks so that intended movements reliably produce expected, non-threatening sensory outcomes, therapy promotes new predictions that movement is safe and effective, encouraging more vigorous engagement.

This perspective also clarifies the role of augmented feedback in therapy and neuroprosthetic training. Visual, haptic, or auditory feedback that is temporally aligned with intended actions can accelerate the updating of internal models. However, if feedback is inconsistent, delayed, or poorly mapped to patient-generated commands, it may increase prediction errors and undermine learning. Designing feedback to respect principles of temporal integration—matching expected latencies and smoothing transient noise—helps patients attribute sensory consequences accurately to their own actions, reinforcing agency and trust in new sensorimotor contingencies. In virtual reality–based rehabilitation, careful calibration of visual delays and gains is therefore critical to prevent maladaptive recalibration that might hinder real-world performance.

Brain-machine interfaces and neuroprosthetic devices stand to benefit directly from leveraging the brain’s anticipatory coding. Motor cortex and related regions encode intended future states of the limb before overt movement; decoders that extract these predictive signals can drive prosthetic effectors in a way that compensates for hardware and communication delays. Rather than interpreting neural activity as a snapshot of current kinematics, neuroprosthetic controllers can be trained to estimate the near-future trajectory the user intends. This approach smooths control, reduces apparent lag, and allows the prosthesis to move ā€œahead of timeā€ relative to feedback, aligning artificial actuation more closely with the user’s internal predictions.

Invasive and noninvasive BMIs can further exploit probabilistic decoding strategies inspired by the bayesian brain hypothesis. Because neural activity is noisy and often recorded from limited populations, decoders that maintain a distribution over possible intended movements—rather than a single deterministic estimate—can better accommodate uncertainty. By combining long-term priors about typical movement patterns (e.g., common reach directions, preferred speeds, or habitual synergies) with moment-to-moment neural signals, BMIs can infer the most likely intended action even when signals are partially degraded. This is especially relevant for patients with progressive conditions, where neural representations may drift over time; adaptive decoders that continuously update their priors based on recent performance maintain alignment with evolving neural codes.

Closed-loop neuroprosthetic systems that integrate sensory feedback also benefit from predictive principles. Sensory substitution via intracortical microstimulation, peripheral nerve stimulation, or wearable haptic devices introduces new feedback channels that the brain must learn to interpret. If the temporal relationship between motor commands, prosthetic movement, and artificial feedback is consistent and matches the user’s internal expectations, the new signals can be incorporated into existing forward models. Training protocols can gradually adjust stimulation timing and intensity to optimize alignment with the user’s predictions, reinforcing the sense of ownership and agency over the prosthetic. Conversely, misaligned feedback may be discounted or even treated as external noise, limiting functional integration.

For individuals with spinal cord injury, hybrid systems that combine residual voluntary control, functional electrical stimulation (FES), and robotic exoskeletons exemplify the importance of prediction-aware design. Users often retain some motor planning capability even when output pathways are disrupted. Interfaces that interpret residual EMG, EEG, or cortical signals as indicators of intended future states can trigger preemptive FES patterns or exoskeleton trajectories that unfold in synchrony with the user’s internal timing. Training must focus on aligning the device’s predictive model with the user’s, so that when the person intends to initiate a movement, the assistive system responds with appropriate anticipation rather than lagging behind or acting prematurely.

Rehabilitation robotics can explicitly implement computational models of anticipatory control to shape assistance and challenge. Controllers based on optimal feedback control or model predictive control can adjust the level and timing of assistance to encourage patients to generate their own predictive commands while still ensuring safety. For example, a robotic exoskeleton might initially provide strong feedforward torques that compensate for gravity and known disturbances, gradually reducing this support as the patient’s internal models improve. Perturbation-based training can then be introduced, where the robot occasionally alters dynamics in controlled ways to provoke prediction errors that drive adaptation. The aim is to guide the nervous system toward more accurate internal models and robust anticipatory strategies, not to permanently offload control to the machine.

Insights from dynamical systems models of neural control also inform prosthetic design. If preparatory neural states correspond to specific trajectories through a low-dimensional manifold, decoders can be developed to map these initial conditions directly onto planned movement sequences. Instead of decoding instantaneous velocity commands at every time step, the system could interpret a transient burst of preparatory activity as a request to execute an entire reaching movement or grasp, which the prosthesis then carries out with its own internal predictive controller. This division of labor allows the brain to focus on specifying desired future outcomes, while the device handles detailed trajectory generation and local feedback corrections.

Prediction-based perspectives are particularly relevant for pediatric rehabilitation and developmental neuroprosthetics. Children’s internal models of body and environment are still forming, making their predictive mechanisms highly plastic but also more vulnerable to distorted experience. Early intervention that provides rich, consistent sensorimotor contingencies—especially when assistive technology is involved—can scaffold the development of accurate forward models. Conversely, poorly calibrated orthoses or prosthetic devices that produce inconsistent or delayed responses may be internalized as part of the child’s expected body dynamics, potentially leading to entrenched maladaptive priors. Designing pediatric devices and training regimens to support the emergence of accurate, flexible predictive control is essential for long-term functional independence.

The concept of retrocausality—behaving as though information from the future were available—serves as a useful metaphor for what well-designed rehabilitation and neuroprosthetic systems should achieve. By anticipating the sensory and mechanical consequences of both biological and artificial actuators, these systems can shape present interventions in a way that aligns with desired future states of function. In practice, this means structuring therapy to emphasize the rehearsal of future-oriented, task-relevant movement patterns, and constructing prosthetic controllers that are tuned not merely to follow the user’s current state but to help realize their intended future states as seamlessly as possible.

Psychological and experiential dimensions of anticipation also matter. The sense of agency, confidence, and trust in one’s body or device strongly depends on the alignment between predicted and actual outcomes. When patients repeatedly experience mismatches—unexpected delays, incorrect device responses, or inconsistent sensory consequences—they may reduce engagement, adopt conservative strategies, or avoid using the affected limb or prosthesis. Conversely, when therapy and technology are organized so that predictions are reliably confirmed, patients are more likely to explore, attempt challenging tasks, and update their internal models in a functional direction. Rehabilitation teams can harness this by carefully managing task difficulty and feedback so that the majority of trials fall within a ā€œsuccessful-but-challengingā€ window that maximizes informative prediction errors without overwhelming the system.

Future clinical pathways may incorporate individualized computational modeling to tailor interventions. By fitting state-space, optimal control, or active inference models to a patient’s movement and neural data, clinicians could infer which components of predictive control are most impaired: is the forward model of limb dynamics inaccurate, is feedback integration overly cautious, or are high-level priors about movement safety excessively restrictive? Interventions could then be selected and parameterized to target these specific deficits—for instance, emphasizing error-based adaptation for forward model recalibration, or graded exposure and success-based training for maladaptive high-level priors. Such model-informed rehabilitation promises more precise, mechanistically grounded treatment plans than one-size-fits-all protocols.

In the domain of neuroprosthetics, adaptive decoders that embody principles of the bayesian brain and active inference can progressively align with the user’s evolving predictive strategies. Early in training, the decoder might rely heavily on robust priors about generic reaching or grasping patterns, gradually shifting weight toward user-specific neural signatures as data accumulates. Simultaneously, the device can present the user with consistent, temporally precise feedback that facilitates the brain’s incorporation of the prosthesis into its internal body schema. Over time, the boundary between biological and artificial components becomes less functionally relevant: both participate in a shared predictive loop that jointly minimizes prediction error and supports smooth, anticipatory control of movement.

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