Simulated Visual Field Loss Does Not Alter Turning Coordination in Healthy Young Adults

Turning, while walking, is an important component of adaptive locomotion. Current hypotheses regarding the motor control of body segment coordination during turning suggest heavy influence of visual information. The authors aimed to examine whether visual field impairment (central loss or peripheral loss) affects body segment coordination during walking turns in healthy young adults. No significant differences in the onset time of segments or intersegment coordination were observed because of visual field occlusion. These results suggest that healthy young adults can use visual information obtained from central and peripheral visual fields interchangeably, pointing to flexibility of visuomotor control in healthy young adults. Further study in populations with chronic visual impairment and those with turning difficulties are warranted.     

Development of rule-based eye-hand-decoupling in children and adolescents

In the present study, we characterize how the ability to decouple guiding visual information from a motor action emerges during childhood and adolescence. Sixty-two participants (age range 8–15 yrs.) completed two eye-hand coordination tasks. In a direct interaction task, vision and motor action were in alignment, and participants slid their finger along a vertical touch screen to move a cursor from a central target to one of four peripheral targets. In an eye-hand-decoupled task, eye and hand movements were made in different planes and cursor feedback was 180° reversed. We analyzed whether movement planning, timing and trajectory variables differed across age in both task conditions. There were no significant relationships between age and any movement planning, timing, or execution variables in the direct interaction task. In contrast, in the eye-hand-decoupled task, we found a relationship between age and several movement planning and timing variables. In adolescents (13–15 yrs.), movement planning and timing was significantly shorter than that of young children (8–10 yrs.). Eye-hand-decoupled maturation emerged mainly during late childhood (11–12 yrs.). Notably, we detected performance differences between young children and adolescents exclusively during the eye-hand decoupling task which required the integration of rule-based cognitive information into the motor action. Differences were not observed during the direct interaction task. Our results quantify an important milestone for eye-hand-decoupling development in late childhood, leading to improved rule-based motor performance in early adolescence. This eye-hand-decoupling development may be due to frontal lobe development linked to rule-based behavior and the strengthening of fronto-parietal networks.     

Quiet Eye Training Improves Small Arms Maritime Marksmanship

Quiet eye training—teaching task-specific gaze control—has been consistently shown to optimize the acquisition of motor skills. The present study aimed to examine the potential benefits of a quiet eye training intervention in a simulated maritime marksmanship task that involved shooting fast approaching moving targets with a decommissioned general-purpose machine gun. Twenty participants were randomly assigned to a quiet eye trained (QET) or technical trained (TT) group and completed 2 baseline, 20 training, and 2 retention trials on the moving-target task. Compared to their TT counterparts, the QET group displayed more effective gaze control (longer quiet eye durations and greater target locking) and more accurate performance (smaller radial error of both the initial shot and average of all shots) at retention. These findings highlight the potential for quiet eye training to be used to support the training of marksmanship skills in military settings.     

New knowledge derived from learned knowledge: functional-anatomic correlates of stimulus equivalence

Forming new knowledge based on knowledge established through prior learning is a central feature of higher cognition that is captured in research on stimulus equivalence (SE). Numerous SE investigations show that reinforcing behavior under control of distinct sets of arbitrary conditional relations gives rise to stimulus control by new, derived relations. This investigation examined whether frontal-subcortical and frontal-parietal networks known to support reinforced conditional relations also support derived conditional relations. Twelve adult subjects completed matching-to-sample (MTS) training with correct/wrong feedback to establish four trained conditional relations within two distinct, three-member stimulus classes: (1) A1-->B1, B1-->C1 and (2) A2-->B2, B2-->C2. Afterwards, functional neuroimaging was performed when MTS trials were presented involving matching two identical circles (a sensorimotor control condition), trained relations (A-->B, B-->C), and derived relations: symmetry (B-->A, C-->B), transitivity (A-->C), and equivalence (C-->A). Conditional responding to trained and derived relations was similarly correlated with bilateral activation in the targeted networks. Comparing trained to derived relations, however, highlighted greater activation in several prefrontal regions, the caudate, thalamus, and putamen, which may represent the effects of extended training or feedback present during imaging. Each derived relation also evidenced a unique activation pattern. Collectively, the findings extend the role of frontal-subcortical and frontal-parietal networks to derived conditional relations and suggest that regional involvement varies with the type of derived conditional relation.     

Action observation produces motor resonance in Parkinson's disease

Observation of movement activates the observer's own motor system, influencing the performance of actions and facilitating social interaction. This motor resonance is demonstrated behaviourally through visuomotor priming, whereby response latencies are influenced by the compatibility between an intended action and an observed (task‐irrelevant) action. The impact of movement disorders such as Parkinson's disease (PD) on motor resonance is unclear, as previous studies of visuomotor priming have not separated imitative compatibility (specific to human movement) from general stimulus‐response compatibility effects. We examined visuomotor priming in 23 participants with mild‐to‐moderate PD and 24 healthy older adults, using a task that pitted imitative compatibility against general stimulus‐response compatibility. Participants made a key press after observing a task‐irrelevant moving human finger or rectangle that was either compatible or incompatible with their response. Imitative compatibility effects, rather than general stimulus‐response compatibility effects, were found specifically for the human finger. Moreover, imitative compatibility effects did not differ between groups, indicating intact motor resonance in the PD group. These findings constitute the first unambiguous demonstration of imitative priming in both PD and healthy ageing, and have implications for therapeutic techniques to facilitate action, as well as the understanding of social cognition in PD.     

Effects of Visual Error Timing on Smooth Pursuit Gain Adaptation in Humans

Smooth pursuit (SP) is one of the precise oculomotor behaviors when tracking a moving object. Adaptation of SP is based on a visual-error driven motor learning process associated with predictable changes in the visual environment. Proper timing of a sensory signal is an important factor for adaptation of fine motor control. In this study, we investigated whether visual error timing affects SP gain adaptation. An adaptive change in SP gain is produced experimentally by repeated trials of a step-ramp tracking with 2 different velocities (double-velocity paradigm). The authors used the double-velocity paradigm where target speed changes 400 or 800 ms after the target onset. The results show that SP gain changed in a certain time window following adaptation. The authors suggest that SP adaptation shown in this study is associated with timing control mechanisms.     

Go/No-Go范式中非反应手状态对Simon效应性质的影响

为了探讨非反应手对标准Simon任务改装的go/no-go任务的影响,被试只对其中一种颜色进行按键反应,通过指导语来操控非反应手的状态,结果发现：(1)实验一中当不提醒非反应手如何放置时,不会产生Simon效应;(2) 实验二中要求非反应手放在固定的桌面位置上,产生了视觉运动Simon效应,其随反应时的增大而减小;(3) 实验三中要求非反应手放在固定的非反应键上,却产生了认知Simon效应,其随反应时的增大而增大。这说明非反应手的状态影响Simon效应的产生及其性质。     

Near,Far, or In Between?—Target Edges and the Transport Component of Prehension

It is well known that during visually guided prehension movements the peak velocity of the arm is scaled for object distance (e.g., Gentilucci et al., 1991; Jakobson & Goodale, 1991; Servos, Goodale, & Jakobson, 1992). Those movements are being directed not to single points in space, however, but rather to objects with extent. Thus, object distance must be computed relative to some particular point on the object. Whether that point corresponds to the location of a particular edge, for example, has not been clearly demonstrated. In the present study, subjects (N = 9) were presented with a series of oblong blocks positioned at different locations. Peak velocity increased with object size for reaches in which different-sized objects had their near edges lined up; in contrast, the peak velocities of reaches directed to objects of different sizes did not differ when the far edges of the objects were lined up. The present study, therefore, provided confirmation that subjects calibrate the peak velocity of their reaches relative to the far edge of a target object.     

Visual Dominance in Amending the Directional Parameter of Feedforward Control

The authors examined visual dominance between trials in which the movement program was amended (i.e., off-line processing). Weighting between visual and proprioceptive feedback was examined in a trial-by-trial analysis of the directional parameter of feedforward control. Eight participants moved a cursor to a target displayed on a computer screen by manipulating a hand-held stylus on a digitizing tablet. In the first 30 trials, the cursor followed the stylus movement (practice condition). In the next 30 trials, the directional error of the stylus movement was presented in the opposite direction (reversal condition). Subjects knew the presence and the nature of the reversal. In the last 10 trials, the reversal was withdrawn (transfer condition). Directional error of feedforward control was relatively small in the practice condition, and it increased gradually in 1 of 2 directions as trials proceeded in the reversal condition. Positive aftereffect was observed in the transfer condition. A constant increment of the directional error indicated that both visual and proprioceptive feedback are registered, with higher weight on vision, and that weighting between those inputs is determined automatically or is fixed without any strategic control.     

Informational constraints on spontaneous visuomotor entrainment

Past research has revealed that an individual’s rhythmic limb movements become spontaneously entrained to an environmental rhythm if visual information about the rhythm is available and its frequency is near that of the individual’s movements. Research has also demonstrated that if the eyes track an environmental stimulus, the spontaneous entrainment to the rhythm is strengthened. One hypothesis explaining this enhancement of spontaneous entrainment is that the limb movements and eye movements are linked through a neuromuscular coupling or synergy. Another is that eye-tracking facilitates the pick up of important coordinating information. Experiment 1 investigated the first hypothesis by evaluating whether any rhythmic movement of the eyes would facilitate spontaneous entrainment. Experiments 2 and 3 (respectively) explored whether eye-tracking strengthens spontaneous entrainment by allowing the pickup of trajectory direction change information or allowing an increase in the amount of information to be picked-up. Results suggest that the eye-tracking enhancement of spontaneous entrainment is a consequence of increasing the amount of information available to be picked-up.