A kinematic comparison of successful and unsuccessful tennis serves across the elite development pathway

While velocity generation is an obvious prerequisite to proficient tennis serve performance, it is also the only stroke where players are obliged to negotiate a unique target constraint. Therefore, the dearth of research attending to the accuracy component of the serve is surprising. This study compared the body, racquet and ball kinematics characterising successful serves and service faults, missed into the net, in two groups of elite junior female players and one professional female tennis player. Three-dimensional body, racquet and ball kinematics were recorded using a 22-camera VICON motion analysis system. There were no differences in body kinematics between successful serves and service faults, suggesting that service faults cannot be attributed to a single source of biomechanical error. However, service faults missing into the net are characterized by projection angles significantly further below the horizontal, implying that consistency in this end-point parameter is critical to successful performance. Regulation of this parameter appears dependent on compensatory adjustments in the distal elbow and wrist joints immediately prior to impact and also perceptual feedback. Accordingly, coordination of the distal degrees of freedom and a refined perception-action coupling appear more important to success than any isolated mechanical component of the service action.     

Neural binding of space and time: An introduction

Some of the central problems to be solved by the brain, such as figure-ground coding and object recognition, concern the binding of separately coded feature elements into coherent object representations. The binding problem has recently been approached by a variety of disciplines, notably psychophysics and experimental psychology, electrophysiology and neurophysiology, and computational modelling. This Special Issue brings together 21 of papers, mainly all from psychology and computational modelling, that address issues in Gestalt formation, the relation of the grouping and binding processes to visual attention, the role of temporal factors for grouping and binding, the neuronal correlates of binding mechanisms, the development of binding operations in infants, and the breakdown of these processes following brain damage.     

Everyday Cognitive Functioning in Cardiac Patients: Relationships Between Self-report,Report of a Significant Other and Cognitive Test Performance

ABSTRACT

Candidates for cardiac bypass surgery often experience cognitive decline. Such decline is likely to affect their everyday cognitive functioning. The aim of the present study was to compare cardiac patients' ratings of their everyday cognitive functioning against significant others' ratings and selected neuropsychological tests. Sixty-nine patients completed a battery of standardised cognitive tests. Patients and significant others also completed the Everyday Function Questionnaire independently of each other. Patient and significant other ratings of patients' everyday cognitive difficulties were found to be similar. Despite the similarities in ratings of difficulties, some everyday cognitive tasks were attributed to different processes. Patients' and significant others' ratings were most closely associated with the neuropsychological test of visual memory. Tests of the patients' verbal memory and fluency were only related to significant others' ratings. Test scores of attention and planning were largely unrelated to ratings by either patients or their significant others.     

The Impact of Strategic Trajectory Optimization on Illusory Target Biases During Goal-Directed Aiming

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 Elliott, D., Hansen, S., Grierson, L. E. M., Lyons, J., Bennett, S. J., &; Hayes, S. J. (2010). Goal-directed aiming: two components but multiple processes. Psychological Bulletin, 136, 1023–1044.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]).     

The Impact of Real and Illusory Perturbations on the Early Trajectory Adjustments of Goal-Directed Movements

Examinations of goal-directed movements reveal a process of control that operates to make adjustments on the basis of the expected visual afference associated with the limb's movement. This experiment examined the impact of perturbations to the perceived and actual velocity of aiming movements when each was presented alone or in tandem with the other. Perturbations to perceived velocity were achieved by translating the background over which aiming movements were performed. An aiming stylus that discharged air either in the direction of the movement or in the direction opposite the movement generated the actual velocity perturbations. Kinematic analyses of the aiming movements revealed that only the actual perturbation influenced the control of early movement trajectories. The results are discussed with respect to the influence that visual information has on the control exerted against physical perturbations. Speculations are raised regarding how potential for perturbations influences the strategies adopted for minimizing their impact.     

Coupling of Eye,Finger, Elbow,and Shoulder Movements During Manual Aiming

Temporal and spatial coupling of point of gaze (PG) and movements of the finger, elbow, and shoulder during a speeded aiming task were examined. Ten participants completed 40-cm aiming movements with the right arm, in a situation that allowed free movement of the eyes, head, arm, and trunk. On the majority of trials, a large initial saccade undershot the target slightly, and 1 or more smaller corrective saccades brought the eyes to the target position. The finger, elbow, and shoulder exhibited a similar pattern of undershooting their final positions, followed by small corrective movements. Eye movements usually preceded limb movements, and the eyes always arrived at the target well in advance of the finger. There was a clear temporal coupling between primary saccade completion and peak acceleration of the finger, elbow, and shoulder. The initiation of limb-segment movement usually occurred in a proximal-to-distal pattern. Increased variability in elbow and shoulder position as the movement progressed may have served to reduce variability in finger position. The spatial-temporal coupling of PG with the 3 limb segments was optimal for the pick up of visual information about the position of the finger and the target late in the movement.     

The influence of environmental context in interpersonal observation–execution

Cyclical upper-limb movements involuntarily deviate from a primary movement direction when the actor concurrently observes incongruent biological motion. We examined whether environmental context influences such motor interference during interpersonal observation–execution. Participants executed continuous horizontal arm movements while observing congruent horizontal or incongruent curvilinear biological movements with or without the presence of an object positioned as an obstacle or distractor. When participants were observing a curvilinear movement, an object located within the movement space became an obstacle, and, thus, the curvilinear trajectory was essential to reach into horizontal space. When acting as a distractor, or with no object, the curvilinear trajectory was no longer essential. For observing horizontal movements, objects were located at the same relative locations as in the curvilinear movement condition. We found greater involuntary movement deviation when observing curvilinear than horizontal movements. Also, there was an influence of context only when observing horizontal movements, with greater deviation exhibited in the presence of a large obstacle. These findings suggest that the influence of environmental context is underpinned by the (mis-)matching of observed and executed actions as incongruent biological motion is primarily coded via bottom-up sensorimotor processes, whilst the congruent condition incorporates surrounding environmental features to modulate the bottom-up sensorimotor processes.     

Cross‐Linguistic Differences in Digit Memory Span

This study investigated whether the better performance of the Chinese in digit memory span tasks was due only to the shorter pronunciation duration of Chinese digit names, or to enhanced visuospatial sketchpad abilities, or to both. Results of the experiment showed that the Chinese outperformed their Malay counterparts in digit memory span tasks because Chinese digit names had shorter pronunciation durations than Malay digit names and not because the Chinese had better visuospatial sketchpad abilities than the Malays. The results thus support Baddeley's phonological loop hypothesis as an account for cross‐linguistic differences in digit memory spans. Because memory traces are subject to decay and the phonological store is temporally limited, the shorter the pronunciation duration of digit names in a language, the more digits one can rehearse within a limited time period, and therefore the larger is one's short‐term digit span in that language.     

Opposing amygdala and ventral striatum connectivity during emotion identification

Lesion and electrophysiological studies in animals provide evidence of opposing functions for subcortical nuclei such as the amygdala and ventral striatum, but the implications of these findings for emotion identification in humans remain poorly described. Here we report a high-resolution fMRI study in a sample of 39 healthy subjects who performed a well-characterized emotion identification task. As expected, the amygdala responded to THREAT (angry or fearful) faces more than NON-THREAT (sad or happy) faces. A functional connectivity analysis of the time series from an anatomically defined amygdala seed revealed a strong anticorrelation between the amygdala and the ventral striatum/ventral pallidum, consistent with an opposing role for these regions in during emotion identification. A second functional connectivity analysis (psychophysiological interaction) investigating relative connectivity on THREAT vs. NON-THREAT trials demonstrated that the amygdala had increased connectivity with the orbitofrontal cortex during THREAT trials, whereas the ventral striatum demonstrated increased connectivity with the posterior hippocampus on NON-THREAT trials. These results indicate that activity in the amygdala and ventral striatum may be inversely related, and that both regions may provide opposing affective bias signals during emotion identification.     

Poor Imitative Performance of Unlearned Gestures in Children with Probable Developmental Coordination Disorder

It has been hypothesized that deficits in imitation, linked to abnormal functioning of the mirror neuron system (MNS), may contribute to the motor impairments associated with developmental coordination disorder (DCD). The authors aimed to examine imitation of complex novel postures and sequences of gestures in children with and without probable DCD (pDCD), using the postural praxis and sequencing praxis subtests of the Sensory Integration and Praxis Tests (Ayres, 1989 Ayres, A. J. (1989). Sensory Integration and Praxis Tests: SIPT manual. Los Angeles, CA: Western Psychological Services. [Google Scholar]). Participants were 29 boys with pDCD between 6.08 and 13.33 years old, and 29 group age-matched typically developing boys between 6.08 and 13.83 years old. Responses of children with pDCD on both imitation tasks were less accurate than controls, with group differences more apparent with increasing task complexity. Furthermore, as a group, children with pDCD were slower and had a higher number of non–mirror-imitated responses. There was considerable variability within the pDCD group, with some children displaying imitation scores within the normative range. Given the importance of imitation and visual learning for motor development, the difficulties in imitation displayed by some children with pDCD have the potential to impact on movement acquisition. Interventions to target imitation may be beneficial for these children. The results show that children with pDCD had difficulty imitating complex novel postures, children with pDCD had difficulty imitating gesture sequences, children with pDCD had slower responses than controls, group differences in imitation performance increased with task complexity, and not all children with pDCD displayed imitation deficits.