Calibration is both functional and anatomical

Facilitated adaptation via structural learning increases bimanual interference

Bimanual coordination is an essential feature of the motor system, yet interactions between the limbs during independent control remain poorly understood. Interference between the two hands, or the assimilation of movement characteristics between the two effectors, can be induced by perturbing one arm (e.g., via visuomotor rotation) and then measuring the effects in the contralateral limb. In this study, we sought to further determine the role adaptation plays in bimanual interference using a structural learning paradigm to alter feedback regulation in reaching. We trained healthy participants to counter 60 unique random rotations in right hand visual feedback over 240 reaches. Following this, we assessed feedforward and feedback measures of interference in a bimanual reaching task where the right hand was exposed to a fixed visual feedback rotation while the left hand reached without visual feedback. We found that participants who had been exposed to the structural training task in the right hand showed increased left hand interference during the first 20 trials of the test task. Moreover, interference was greater in feedback, rather than feedforward control parameters. The results further suggest that structural learning enhances bimanual interference via sensory feedback upregulation.

The effects of testing environment, experimental design, and ankle loading on calibration to perturbed optic flow during locomotion

Calibration is the process by which the execution of actions becomes scaled to the (changing) relationship between environmental features and the actor's action capabilities. Though much research has investigated how individuals calibrate to perturbed optic flow, it remains unclear how different experimental factors contribute to the magnitude of calibration transfer. In the present study, we assessed how testing environment (Experiment 1), an adapted pretest-calibration-posttest design (Experiment 2), and bilateral ankle loading (Experiment 3) affected the magnitude of calibration to perturbed optic flow. We found that calibration transferred analogously to real-world and virtual environments. Although the magnitude of calibration transfer found here was greater than that reported by previous researchers, it was evident that calibration occurred rapidly and quickly plateaued, further supporting the claim that calibration is often incomplete despite continued calibration trials. We also saw an asymmetry in calibration magnitude, which may be due to a lack of appropriate perceptual-motor scaling prior to calibration. The implications of these findings for the assessment of distance perception and calibration in real-world and virtual environments are discussed.

Sensorimotor adaptation and cue reweighting compensate for distorted 3D shape information, accounting for paradoxical perception-action dissociations

Visually guided movements can show surprising accuracy even when the perceived three-dimensional (3D) shape of the target is distorted. One explanation of this paradox is that an evolutionarily specialized “vision-for-action” system provides accurate shape estimates by relying selectively on stereo information and ignoring less reliable sources of shape information like texture and shading. However, the key support for this hypothesis has come from studies that analyze average behavior across many visuomotor interactions where available sensory feedback reinforces stereo information. The present study, which carefully accounts for the effects of feedback, shows that visuomotor interactions with slanted surfaces are actually planned using the same cue-combination function as slant perception and that apparent dissociations can arise due to two distinct supervised learning processes: sensorimotor adaptation and cue reweighting. In two experiments, we show that when a distorted slant cue biases perception (e.g., surfaces appear flattened by a fixed amount), sensorimotor adaptation rapidly adjusts the planned grip orientation to compensate for this constant error. However, when the distorted slant cue is unreliable, leading to variable errors across a set of objects (i.e., some slants are overestimated, others underestimated), then relative cue weights are gradually adjusted to reduce the misleading effect of the unreliable cue, consistent with previous perceptual studies of cue reweighting. The speed and flexibility of these two forms of learning provide an alternative explanation of why perception and action are sometimes found to be dissociated in experiments where some 3D shape cues are consistent with sensory feedback while others are faulty.

NEW & NOTEWORTHY When interacting with three-dimensional (3D) objects, sensory feedback is available that could improve future performance via supervised learning. Here we confirm that natural visuomotor interactions lead to sensorimotor adaptation and cue reweighting, two distinct learning processes uniquely suited to resolve errors caused by biased and noisy 3D shape cues. These findings explain why perception and action are often found to be dissociated in experiments where some cues are consistent with sensory feedback while others are faulty.

Search Strategies in the Perceptual-Motor Workspace and the Acquisition of Coordination, Control, and Skill

In this paper we re-visit and elaborate-on the theoretical framework of learning as searching within the perceptual-motor workspace for a solution to the task. The central focus is the nature of search strategies to locate and create stable equilibrium regions in the perceptual-motor workspace and how these strategies relate to the emergent movement forms in the acquisition of coordination, control, and skill. In the ecological theory of perception and action, the enhanced stability of performance occurs through the attunement of the perceptual systems to the task dynamics together with modifications of action as task and intrinsic dynamics cooperate and/or compete. Thus, through practice in this search process, individuals adapt to the pick-up of task relevant perceptual variables and change their movement form according to the stability of the performed action and its outcome in relation to the task demands. Contemporary experimental findings have revealed features of the search process given the interaction of individual intrinsic dynamics in the context of task requirements and principles that drive the change – e.g., exploitation of more tolerant task-space solutions and emergence of compensatory mechanisms. Finally, we outline how the search strategy framework relates to traditional learning-related phenomena: including the dynamical pathways of learning, learning curves, factors of learning, individuality, motor development, and sport and rehabilitation interventions.

Regular physical activity modulates perceived visual speed when running in treadmill-mediated virtual environments

In virtual reality, visual speed is usually underestimated relative to locomotor speed. Here we investigated how physical activity and fitness affect perceived visual speed when running in a treadmill-mediated virtual environment. Thirty healthy participants (ten sedentary individuals, ten team sport players and ten expert runners) ran on a treadmill at two different speeds (8, 12km/h) in front of a moving virtual scene. Participants were asked to match the speed of the visual scene to their running speed (i.e. treadmill speed), indicating for each trial whether the scene was moving slower or faster than the treadmill. The speed of the visual scene was adjusted according to the participant’s response using a staircase until visual and running speeds were perceived as equivalent. More sedentary participants underestimated visual speed relative to their actual running speed. Specifically, visual speed had to exceed running speed to be perceived as equivalent. The underestimation of visual speed was speed-dependent, and it was significantly larger for sedentary participants than for team sports players and expert runners. The volume of physical activity per week was found to be the best predictor of visual speed perception for both running speeds, while the perceived effort constituted a good predictor only at 8km/h. Physical fitness, on the other hand turned out to be a poor predictor of visual speed perception. Therefore, in order to enhance users’ engagement and their adherence to physical activity programs, the development of “personalized” treadmill-mediated virtual environments should take into account users’ personal characteristics to provide the most natural and engaging feedback possible.

Anxiety Influences the Perceptual-Motor Calibration of Visually Guided Braking to Avoid Collisions

We investigated whether anxiety influences perceptual-motor calibration in a braking to avoid a collision task. Participants performed either a discrete braking task (Experiment 1) or a continuous braking task (Experiment 2), with the goal of stopping before colliding with a stop sign. Half of participants performed the braking task after an anxiety induction. We investigated whether anxiety reduced the frequency of crashing and if it influenced the calibration of perception (visual information) and action (brake pressure) dynamically between-trials in Experiment 1 and within-trials in Experiment 2. In the discrete braking task, anxious participants crashed less often and made larger corrective adjustments trial-to-trial after crashing, suggesting that the influence of anxiety on behavior did not occur uniformly, but rather dynamically with anxiety amplifying the reaction to previous crashes. However, when performing continuous braking, anxious participants crashed more often, and their within-trial adjustments of deceleration were less related to visual information compared to controls. Taken together, these findings suggest that the timescale and nature of the task mediates the influence of anxiety on the performance of goal-directed actions.

Auditory environmental context affects visual distance perception

In this article, we show that visual distance perception (VDP) is influenced by the auditory environmental context through reverberation-related cues. We performed two VDP experiments in two dark rooms with extremely different reverberation times: an anechoic chamber and a reverberant room. Subjects assigned to the reverberant room perceived the targets farther than subjects assigned to the anechoic chamber. Also, we found a positive correlation between the maximum perceived distance and the auditorily perceived room size. We next performed a second experiment in which the same subjects of Experiment 1 were interchanged between rooms. We found that subjects preserved the responses from the previous experiment provided they were compatible with the present perception of the environment; if not, perceived distance was biased towards the auditorily perceived boundaries of the room. Results of both experiments show that the auditory environment can influence VDP, presumably through reverberation cues related to the perception of room size.

The Anatomy of Action Systems: Task Differentiation When Learning an EMG Controlled Game

This study aims to determine to what extent the task for an action system in its initial development relies on functional and anatomical components. Fifty-two able-bodied participants were randomly assigned to one of three experimental groups or to a control group. As a pre- and post-test all groups performed a computer game with the same goal and using the same musculature. One experimental group also trained to perform this test, while the other two experimental groups learned to perform a game that differed either in its goal or in the musculature used. The observed change in accuracy indicated that retaining the goal of the task or the musculature used equally increased transfer performance relative to controls. Conversely, changing either the goal or the musculature equally decreased transfer relative to training the test. These results suggest that in the initial development of an action system, the task to which the system pertains is not specified solely by either the goal of the task or the anatomical structures involved. It is suggested that functional specificity and anatomical dependence might equally be outcomes of continuously differentiating activity.

The Relative Nature of Perception: A Response to Cañal-Bruland and van der Kamp (2015)

Cañal-Bruland and van der Kamp present an argument about the incommensurate relationship between affordance perception and spatial perception in a criticism of Proffitt and Linkenauger’s phenotypic approach to perception. Many of their criticisms are based on a difference in the interpretation of the core ideas underlying the phenotypic approach. The most important of these differences in interpretations concern fundamental assumptions about the nature of the perceptions of size and distance themselves. Extent perception must be relative to the organism; therefore, there can be no veridical perception of space. Also, we argue in the phenotypic approach that space perception is an emergent property of affordance perception; they are not different types of perceptions as Cañal-Bruland and van der Kamp presume. Third, affordance perception need not be perfectly accurate, just good enough. Additionally, affordance perception need not be dichotomous; this presumption likely originates in the methodology typically employed to study affordance perception. Finally, I agree with Cañal-Bruland and van der Kamp that joint research efforts will clarify and improve our understanding of these issues.

Transfer of attunement in length perception by dynamic touch

Earlier studies have revealed that the calibration of an action sometimes transfers in a functionally specific way—the calibration of one action transfers to other actions that serve the same goal, even when they are performed with different anatomical structures. In the present study, we tested whether attunement (the process by which perceivers learn to detect a more useful, specifying, informational pattern) follows such a functional organization. Participants were trained to perceive the length of rods by dynamic touch with one of their effectors. It was found that training the right hand resulted in an attunement to a specifying variable with both hands, but not with the feet. Training the other limbs did not result in attunement. However, substantial individual differences were found. The implications of the results are explored for theories on the organization of perceptual learning and discussions on individual differences in perception.