Journal of Motor Behavior最新文献

Researchers have investigated the sensorimotor mechanisms that result in Fitts' law. One approach has been to analyse movement trajectories during Fitts' tasks to reveal the processes that occur during movement preparation and execution. We used trajectory analysis in the current study to investigate how limb-target control contributed to Fitts' law during the transition from ballistic movements to movements with online control. Twenty-five participants made discrete reaching movements in seven conditions with indexes of difficulty that ranged from one to seven. There were strong linear relationships between index of difficulty, effective index of difficulty and movement time. Trajectory analysis suggested that the easiest condition had movements that were mostly ballistic. There was enough time for visual-based online corrections, but the condition was probably too easy to require limb-target control. Trajectory analysis also suggested that there was an increased reliance on limb-target control as the index of difficulty increased. In conclusion, there was a strong linear relationship between effective index of difficulty and movement time even with conditions that ranged from mostly ballistic to a high degree of limb-target control. We suggest that there is a direct relationship between effective index of difficulty and degree of limb-target control.

Proprioceptive inputs have crucial roles in control of the posture. The aim of the present study was to assess the effect of interfering with these signals on postural stability by ice-induced anaesthesia and local calf muscle fatigue. Seventeen healthy young individuals participated in this study to stand quietly and on an unstable platform under normal, anaesthesia, and fatigue conditions. A force platform calculated excursions of centre of pressure. Stabilogram-diffusion analysis was utilised to evaluate how body controls the posture with and without proprioceptive inputs. Time intervals of using the sensory feedback is significantly increased by anaesthesia in quiet standing (430 ms, p = 0.034) to note more delayed use of sensory information in a closed-loop. Additionally, fatigue significantly increased the time intervals of using sensory feedback during standing on the unstable platform (290 ms, p = 0.016). Interestingly, sensory interventions had no effect on the stability of the open-loop control of posture (short-term control), but they significantly influenced the closed-loop control (long-term control) (p < 0.004). Specifically, fatigue led to increased instabilities when the body used sensory inputs during both quiet standing (p = 0.021) and standing on the unstable platform (p = 0.041). These findings highlight the importance of proprioception in balance control for healthy individuals. Interfering with proprioceptive inputs, either through anaesthesia or fatigue, resulted in instabilities during balance maintenance. Our study provides new insights into the mechanisms underlying postural control, emphasising the significance of proprioceptive inputs. Understanding how proprioception affects balance maintenance may have implications for rehabilitation strategies, injury prevention, and the development of interventions to improve postural stability.

Numerous devices are being developed to assist visually impaired and blind individuals in performing everyday tasks such as reaching out to grasp objects. Considering that the size, weight, and cost of assistive devices significantly impact their acceptance, it would be useful to know how effective various types of guiding information can be. As an initial exploration of this issue, we conducted four studies in which participants with normal vision were visually guided toward targets. They were guided by information about the direction to the target, and either about the distance to the target or about the time required to reach the target. We compared participants' performance when provided with different amounts of each of these kinds of information. We found that restricting information about the distance from the target or the time it would take to reach the target to only a few possible values does not affect performance substantially. Restricting information about the direction to the target to only a few possible values appears to be more detrimental, but the disadvantage of having few possible directions can be mitigated by combining values in multiple directions. These findings can help optimize haptic presentations in assistive technology.

The present experiment used the Serial Reaction Time Task(SRTT) to investigate if auditory cueing or feedback in the form of spatially compatible tones benefited sequence learning similarly. Fifty-three neurotypical adults (18-35 years; 32 cis-females; 21 cis-males) were randomly assigned to three groups in which they practiced a visual SRTT: Group AC was supplemented with auditory cues; group AF received auditory feedback; group NS performed without sound. Retention and transfer tests (i.e., in the other two sensory conditions), and an explicit awareness test were conducted 48 h after practice. Changes in Total Sequence Time (TST), Total Error (TE), and acquired knowledge of the 10-item sequence order quantified sequence learning and were assessed using a two-way mixed ANOVA with repeated measures (p ≤ 0.05). A significant group-by-time interaction indicated only the AC group maintained their performance improvements when the sequence was perturbed. Overall, improvements in TST on day 1 and day 2 were consistent with all groups acquiring task-general and sequence-specific knowledge. TE outcomes suggested no speed-accuracy tradeoff. On Day 2, all groups performed best in the no-sound condition, indicating performance was maintained when sound cues or feedback were removed. All groups acquired equivalent implicit motor sequence knowledge regardless of sound condition.

Individuals post-stroke commonly demonstrate alterations in motor behavior with regard to both task performance and the motor strategies used in pursuit of task goals. We evaluated whether constraining postural sway (motor strategy) during practice would affect upper-limb precision aiming performance (task performance) and postural control adaptations. Adults with stroke stood on a force plate while immersed in a virtual scene displaying an anterior target. Participants aimed to position a virtual laser pointer (via handheld device) in the target. Participants then completed practice trials involving aiming at a lateral target. For this practice session, participants were randomized to either (a) a "constraint" group wherein they received physical constraint to limit postural sway, or (b) a "no-constraint" group. Task performance and postural control were assessed before and after practice, and transfer to another upper-limb task was evaluated. After practice, both groups improved paretic upper-limb performance. For the target task, the no-constraint group showed task-sensitive changes in postural control. The constraint group showed no changes in postural control. At transfer, the constraint group increased postural sway. Constraining postural sway after stroke should be carefully considered with the recognition that postural sway arises from exploratory movements involved in the discovery of adaptable motor solutions.

Cross-education (CE) is a phenomenon whereby motor training of one limb leads to improved performance in the opposite untrained limb. External pacing of a motor task can enhance CE; however, the influence of different pacing methods is poorly understood. This study explored how motor training with auditory (AP) and visual pacing (VP) impacts CE with a visuomotor force target task. Sixty-one participants performed a unimanual motor task. Participants were randomized into a visual (n = 31) or auditory (n = 30) pacing stimuli condition. The primary outcome was cumulative error scores for each hand, before and after visuomotor training. Pacing type did not yield different magnitudes of CE. However, after adjusting for baseline differences, a significant hand (trained vs. untrained) × practice side (dominant or non-dominant) interaction (p = .013, η_p² = .106) and a group main effect (p = .036, η_p² = .165) were observed. Visual pacing resulted in greater improvements in task performance compared to auditory pacing regardless of hand or practice side, while training the dominant limb resulting in a greater interlimb asymmetry regardless of pacing stimulus. These findings have implications for applying pacing strategies during rehabilitation from unilateral injury or neurological impairment.

The functional equivalence model suggests a common internal representation initiates both imagery and execution. This suggestion is supported by the mental chronometry effect, where there is a positive relation between task difficulty (as defined by the Index of Difficulty; ID) and imagined movement time. The present study extends this logic by examining whether imagery captures the spatial trajectory. Participants were initially tasked with the imagery and execution of a rapid aiming movement under different IDs. These initial attempts were adapted to configure auditory tones at early (25%) and late (75%) intervals for a separate set of imagery trials. If a tone had sounded, participants had to estimate post-trial where their imagined limb would have been located. The findings revealed increases in ID that coincided with increases in imagined and executed movement times. However, participant mean and standard deviation of estimated locations revealed limited differences between the early and late tones. Further inspection revealed some evidence for these estimated locations shifting further along in space following more rapid imagined movements. While equivalence is clearly evident within the temporal domain, there is comparatively little to suggest that this logic extends to the resolution required for simulating the spatial characteristics of movement.

Performance of sport-related ballistic motor skills, like ball hitting in golf and baseball, requires wide movements to produce highly fast and spatially accurate movements. In this study, we assessed the effect of movement amplitude on directional accuracy in a ballistic hitting task. Participants performed the task of moving a manual handle over a flat surface to hit with high speed a moveable disc, aiming to propel it towards a frontal target. Five movement amplitudes were compared, ranging from 11.5 cm to 27.5 cm in steps of 4 cm. Kinematic analysis evaluated motions of the handle, disc, and arm joints. Results showed that greater movement amplitudes led to longer acceleration phases, with delayed peak velocities at the handle, shoulder and elbow, leading to higher contact and peak linear velocities of the handle, and higher angular velocities at the shoulder and elbow. Manipulation of movement amplitude led to no evidence for effects on either disc directional accuracy or variability. Results also revealed no evidence for differences in variability of contact velocity, peak velocity and time of peak velocity across movement amplitudes in the shoulder, elbow, and wrist. Our results indicated that greater movement amplitudes in hitting a spatial target lead to increased contact velocity while not affecting directional accuracy or movement variability.

This research examined how changes in task constraints impacted the throwing patterns of children. The study involved 24 children, with an equal number of males and females, aged 5 and 6. The primary task constraints were the orientation of the target (horizontal or vertical hoops) and the size of the ball (diameters of 6 cm or 12 cm). We observed throwing patterns and analyzed kinematic changes in the preferred throws' components. Initially, some children transitioned from using two hands to using one hand, and from underhand to overarm throws, particularly when using the larger balls. However, the preferred pattern for most children was one-hand overarm throwing. The kinematic analysis revealed that the participants adapted their throwing technique based on the size of the ball and the orientation of the hoop. The most significant adjustments occurred in the forearm component in response to changes in the target orientation. Notably, when aiming for a vertical hoop, distinct modifications were observed, including elevating the humerus and pulling the hand backward. These findings support the dynamical systems theory, which explains how movement patterns vary during motor development. The study also discussed the potential benefits of using constraints for skill acquisition in physical education settings.

This study investigated ankle discriminative acuity and performance and measurement consistency for tests undertaken with different joint position exposure times (PETs). Twenty-four participants were tested using a novel Smartphone Proprioception for Ankle Navigation (SPAN) under four PETs, i.e., 0.25s, 0.5s, 0.75s and 1s, delivered in a random sequence, and then re-tested within one week. The results indicated a PET main effect (F = 10.12, p = 0.004, partial ƞ2 = 0.14), and limb preference main effect (F = 5.39, p = 0.03, partial ƞ2 = 0.19), without significant interactions (p > 0.05). Ankle proprioception improved with prolonged PET, with the non-dominant side outperforming the dominant side. A PET of 0.25s showed good to excellent reliability, with intraclass correlation coefficients (ICCs) of 0.897 (95%CI: 0.761, 0.955) and 0.885 (95%CI: 0.736, 0.951), with standard errors of measurements (SEM) between 0.030 and 0.035, and minimum detectable change at 90% (MDC₉₀) between 0.070 and 0.082, compared to poor to moderate reliability at the other three longer PETs (ICCs =0.352-0.736). The findings suggested the prolongation of PET can improve ankle proprioceptive performance but can amplify the inter-occasion variability, likely due to increased cognitive analysis with longer stimulus sampling. SPAN may thus be a cost-effective and accessible apparatus for clinical practice.