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The failure of perceptual illusions to elicit corresponding biases within movement supports the view of two visual pathways separately contributing to perception and action. However, several alternative findings may contest this overarching framework. The present study aimed to examine the influence of perceptual illusions within the planning and control of aiming. To achieve this, we manipulated and measured the planning/control phases by respectively perturbing the target illusion (relative size-contrast illusion; Ebbinghaus/Titchener circles) following movement onset and detecting the spatiotemporal characteristics of the movement trajectory. The perceptual bias that was indicated by the perceived target size estimates failed to correspondingly manifest within the effective target size. While movement time (specifically, time after peak velocity) was affected by the target configuration, this outcome was not consistent with the direction of the perceptual illusions. These findings advocate an influence of the surrounding contextual information (e.g., annuli) on movement control that is independent of the direction predicted by the illusion. [ABSTRACT FROM AUTHOR]

Investigations of visually guided target-directed movement frequently adopt measures of within-participant spatial variability to infer the contribution of planning and control. The present study aims to verify this current trend by exploring the distribution of displacements at kinematic landmarks with a view to understand the potential sources of variability. Separate sets of participants aiming under full visual feedback conditions revealed a comparatively normal distribution for the displacements at peak velocity and movement end. However, there was demonstrable positive skew in the displacement at peak acceleration and a significant negative skew at peak deceleration. The ranges of the distributions as defined by either ±1SD or ±34.13th percentile (equivalent to an estimated 68.26% of responses) also revealed differences at peak deceleration. These findings indicate that spatial variability in the acceleration domain features highly informative systematic, as well as merely inherent, sources of variability. Implications for the further quantification of trial-by-trial behavior are discussed. [ABSTRACT FROM AUTHOR]

Contemporary models of sensorimotor control contend that visually regulated movement adjustments may unfold early during a target-directed limb movement through an impulse control process that makes use of anticipatory forward models. To date, evidence surrounding impulse control has involved adjustments to a purported misperception in limb velocity following the unexpected onset of a moving background. That is, the limb is perceived to move faster and undershoots more when there is an incongruent moving background and vice versa. However, this particular behavior may manifest from an independent oculo-manual-following response. The present study aimed to deconstruct these proposals and, with them, the processes that underlie impulse control. Participants had to rapidly reach upward to land their index finger accurately on a target. On 33% of trials, the background, over which the movement was made, moved either up, down, right, or left. Displacements in the primary and perpendicular directions of movement showed spatial trajectories that were consistent with the directions of the moving backgrounds. This behavior was most prevalent in measurements taken at the movements' peak negative acceleration and endpoints. Moreover, analysis of standardized displacements in the moving background conditions indicated no significant differences in the extent of the movements toward each of the moving backgrounds. These findings indicate that movement adjustments can manifest from an oculo-manual-following response rather than a misperception of limb velocity. We suggest that the anticipatory forward model that comprises impulse control may incorporate features of the environment that surround the vicinity of the limb. [ABSTRACT FROM AUTHOR]

Early aiming adjustments following an online perturbation are made possible by impulse control. This process may unfold even earlier when perturbations impose a greater risk of a costly overshoot error. Participants executed upward and downward aims to mediate the cost of potential errors-downward overshoots require more energy to correct against gravity. On 33% of the trials, texture elements on the aiming surface were shifted following onset to appear congruent or incongruent with the aiming direction, and consequently generate a misperception of the limb moving slower or faster, respectively. Thus, the risk of potential errors could be influenced by the online perturbation (e.g., increased perceived likelihood of overshooting following the incongruent background). Findings indicated greater undershooting for down compared to up, which reflects the principle of movement optimisation. There was also more undershooting for an incongruent compared to congruent background, which is consistent with early online adjustments counter-acting the misperceived limb velocity. However, there were no interactions throughout the movement trajectory. We suggest that while the initial pre-programme considers the cost of potential errors (target direction), early impulse control fails to discriminate the likelihood of these errors occurring following an online perturbation (moving background). [ABSTRACT FROM AUTHOR]

Recent research has begun to employ interventions that combine action observation and motor imagery (AOMI) with positive results. However, little is known about the underpinning facilitative effect on performance. Participants (n = 50) were randomly allocated to one of five training groups: action observation (AO), motor imagery (MI), simultaneous action observation and motor imagery (S‐AOMI), alternate action observation and motor imagery (A‐AOMI), and control. The task involved dart‐throwing at a concentric circle dartboard at pre‐ and post‐test. Interventions were conducted 3 times per week for 6 weeks. Data were collected from performance outcomes and mean muscle activation of the upper and forearm muscles. Angular velocity and peak angular velocity measurements of the elbow were also collected from the throwing arm. Results showed performance of the A‐AOMI group improved to a significantly greater degree than the AO (P = .04), MI (P = .04), and control group (P = .02), and the S‐AOMI group improved to a greater degree than the control group (P = .02). Mean muscle activation of the triceps brachii significantly reduced in the S‐AOMI and A‐AOMI (P < .01) groups, and participants in the AO (P = .04), A‐AOMI, and S‐AOMI (P < .01) groups significantly reduced activation in the bicep brachii from pre‐ to post‐test. Peak angular velocity significantly decreased from pre‐ to post‐test in both A‐AOMI and S‐AOMI (P < .01) groups. The results reaffirm the benefits of AOMI for facilitating skill learning and provide an insight how these interventions produce favorable changes in EMG and movement kinematics. [ABSTRACT FROM AUTHOR]

During rapid aiming, movements are planned and executed to avoid worst-case outcomes that require time and energy to correct. As such, downward movements initially undershoot the target to avoid corrections against gravity. Illusory target context can also impact aiming bias. Here, the authors sought to determine how strategic biases mediate illusory biases. Participants aimed to Müller-Lyer figures in different directions (forward, backward, up, down). Downward biases emerged late in the movement and illusory biases emerged from peak velocity. The illusory effects were greater for downward movements at terminal endpoint. These results indicate that strategic biases interact with the limb-target control processes associated with illusory biases. Thus, multiple control processes during rapid aiming may combine and later affect endpoint accuracy (D. Elliott et al., 2010 ). [ABSTRACT FROM AUTHOR]

The accuracy and precision of target-directed aiming is contingent upon the availability of online visual feedback. The present study aimed to examine the visual regulation of aiming with blurred vision. The aiming task was executed using a stylus on a graphics digitizing board, which was translated onto a screen in the form of a cursor (representing the moving limb) and target. The vision conditions involved the complete disappearance or blur of the cursor alone, target alone, and cursor+target. These conditions involved leaving the screen uncovered or covering with a diffusing sheet to induce blur. The distance between the screen and sheet was increased to make the blur progressively more severe (0 cm, 3 cm). Results showed significantly less radial and variable error under blurred compared to no vision of the cursor and cursor+target. These findings were corroborated by the movement kinematics including a shorter proportion of time to peak velocity, more negative within-participant correlation between the distances travelled to and after peak velocity, and lower spatial variability from peak velocity to the end of the movement under blurred vision. The superior accuracy and precision under the blurred compared to no vision conditions is consistent with functioning visual regulation of aiming, which is primarily contingent upon the online visual feedback of the moving limb. This outcome may be attributed to the processing of low spatial-high temporal frequencies. Potential implications for low vision diagnostics are discussed. [ABSTRACT FROM AUTHOR]

Directing attention to the effect of one's movement (external focus) has been shown to aid performance compared to directing attention to the movement itself (internal focus). This finding has been predominantly explained by an external focus promoting action planning and automatic movement control, while an internal focus acts to constrain movement (constrained action hypothesis [CAH]). In a separate line of research, the multiple control process model states that early movement phases involve anticipated and feedforward processes, while late movement phases explicitly incorporate external afferent information. We hypothesized that enhanced planning and automatic movement control would manifest from an external/distal focus compared to internal/proximal focus. The present study had participants execute fast and accurate movements to a single target using a digitizing graphics tablet that translated movements to a screen. Participants were instructed to focus on the end target location (external-distal), movement of the cursor (external-proximal), and movement of the limb (internal-proximal). It was found that the external-distal focus generated a shorter time to initiate and execute movements (indicating enhanced movement planning) compared to the external- and internal-proximal conditions. In addition, only the external proximal focus revealed a reduction in spatial variability between peak velocity and movement end (indicating greater online control). These findings indicate that advances in action planning and online control occur when adopting an external-distal focus. However, there were some benefits to online control when adopting an external-proximal focus. We propose that an external-distal focus promotes action-effect principles, where there is a greater contribution of anticipatory feedforward processes that limit the need for late online control. • Explore the sensorimotor processes underpinning attentional focus effects. • External/distal focus accommodates large impulses for shorter movement times. • Internal/proximal focus generates overtly accurate and precise outcomes. • Demarcated focus effects into early (feedforward) and late (feedback) processes [ABSTRACT FROM AUTHOR]

The motor-cognitive model proposes that movement imagery additionally requires conscious monitoring owing to an absence of veridical online sensory feedback. Therefore, it is predicted that there would be a comparatively limited ability for individuals to update or correct movement imagery as they could within execution. To investigate, participants executed and imagined target-directed aiming movements featuring either an unexpected target perturbation (Exp. 1) or removal of visual sensory feedback (Exp. 2). The results of both experiments indicated that the time-course of executed and imagined movements was equally influenced by each of these online visual manipulations. Thus, contrary to some of the tenets of the motor-cognitive model, movement imagery holds the capacity to interpolate online corrections despite the absence of veridical sensory feedback. The further theoretical implications of these findings are discussed. • Executed and imagined movements generate similar neural and behavioural outcomes. • Motor-cognitive model suggests imagery substitutes sensory feedback using attention. • Imagined online corrections were examined via a target shift and removing vision. • Executed and imagined movements had a similar response to these manipulations. • Capacity for imagined movements to interpolate online corrections. [ABSTRACT FROM AUTHOR]