Interacting Constraints and the Emergence of Postural Behavior in ACL-Deficient Subjects

In this study, the authors examined how task, informational, and sensorimotor system constraints influence postural control. Postural behavior of subjects with (n = 15) and without (n = 15) a key sensorimotor system constraint, anterior cruciate ligaments (ACLs) in 1 knee, was examined during 1 - and 2-legged stance with and without vision. Postural control was assessed on a commonly used postural sway meter and on a dynamic stabilometer. Data on postural sway characteristics were obtained for 30 s under 6 different conditions: standing, with eyes open and closed, on both legs, on the injured leg, and on the noninjured leg. The interaction of task, informational, and sensorimotor constraints was observed only on the dynamic stabilometer and not the postural sway meter. Vision was the most important informational constraint on postural control for subjects on the dynamic stabilometer, particularly for the ACL-deficient group standing on the injured leg. Under more static task constraints, ACL deficiency did not prove a significant disadvantage, because vision was confirmed as a significant source of exproprioceptive information. The results support the functionality of using dynamic tasks such as a stabilometer in assessing postural behavior of subjects with sensorimotor system constraints.     

Amplitude Scaling Compensates for Serial Delays in Correcting Eye and Arm Movements

Spatial and metrical parameters of the eye and arm movements made by human subjects (N = 7) in response to visual targets that were stepped unexpectedly either once (single step) or twice (double step) were studied. For the double-step, the displacement of a visual target was decreased or increased in amplitude at intervals before and during a movement. Provided the second target step occurred more than 100 ms before the onset of movement, the amplitude of the subjects' first response was altered in the direction of the new target location. But this amplitude scaling was not always sufficient to reach the new target location, and a second corrective response was required. The latency in producing this second response was greatly increased above reaction time latencies of movements to single-step targets, especially when the target change occurred 100 ms or more before movement onset. These findings suggest that even though serial processing limitations delay the production of a second corrective response, continuous parallel processing of visual information enables the amplitude of the first response to be altered with minimal delay. This enables some degree of real-time continuous control by the visuomotor control system.     

Resolving Power of the Perceptual-and Sensorimotor Systems in 6- to 10-Year-Old Children

Children aged 6 to 10 were tested on their ability to move accurately and to perceptually evaluate their motor response. Subjects performed a directional and an amplitude visuo-manual aiming task without vision of their moving limb. They were asked to correct their error, after completion of their movements, only if they felt they were not accurate. Terminal aiming errors and correction responses (adjustments) were analyzed, and threshold detection was determined relative to terminal aiming error. Action accuracy and evaluation of action accuracy are two abilities that do not develop synchronously. Moreover, the relationship between these abilities depends on whether accuracy and direction or amplitude are required. Amplitude undergoes more corrections than direction, suggesting that the spatial system of reference involved depends more upon the coding of the final position than on direction. Two spatial comparators, operating on the basis of two types of evaluation, seem to have a variably distinct contribution to movement and perception accuracy, according to age.     

Helplessness: The inability to know-that you don’t know-how

The sense of helplessness stands at the very core of the traumatic experience. This paper suggests that a sense of helplessness arises when, despite the functioning of the cognitive system and awareness of circumstances and feelings, an individual is unable to access practical knowledge. As a result, the subject becomes a victim of one’s own inability to perform, or act, in the real world.     

The problems of consciousness and content in theories of perception

The paper aims to show, first, that O’Regan’s and Noë’s Sensorimotor Theory of Vision and Visual Experiences suffers from circularity, and that evidence from empirical research within perception psychology unequivocally invalidates their theory. Secondly, to show that the circularity in O’Regan’s and Noë’s theory of vision and in other general causal and functional theories of perception (i.e. Gibson’s and Marr’s theories of perception) is the inevitable consequence of mutually conflicting assumption of Cartesian dualism underlying these theories. The paper concludes by outlining the consequences of this conflict of assumptions for psychological theories of perception.     

具身记忆及其内在机制

具身记忆研究主要探讨身体及其感觉运动过程在记忆中的作用。操纵或限制身体的物理状态、具身特征或可用性,可以影响记忆的效率、效价和内容。其内在机制可以通过编码特异性原理、启动效应、隐喻表征理论和再激活假说进行解释,但尚未形成统一的模型。基于现有研究与理论的共性,提出具身记忆的感觉运动模拟模型,强调重新激活在具身记忆中的作用,以期在同一框架下说明身体作用于记忆的过程,并进一步指出重新激活的条件。未来亟需在具身记忆的稳定性以及深层机制等方面进行多维度的基础和应用研究。     

Neurocognitive Contributions to Motor Skill Learning: The Role of Working Memory

ABSTRACT

Researchers have begun to delineate the precise nature and neural correlates of the cognitive processes that contribute to motor skill learning. The authors review recent work from their laboratory designed to further understand the neurocognitive mechanisms of skill acquisition. The authors have demonstrated an important role for spatial working memory in 2 different types of motor skill learning, sensorimotor adaptation and motor sequence learning. They have shown that individual differences in spatial working memory capacity predict the rate of motor learning for sensorimotor adaptation and motor sequence learning, and have also reported neural overlap between a spatial working memory task and the early, but not late, stages of adaptation, particularly in the right dorsolateral prefrontal cortex and bilateral inferior parietal lobules. The authors propose that spatial working memory is relied on for processing motor error information to update motor control for subsequent actions. Further, they suggest that working memory is relied on during learning new action sequences for chunking individual action elements together.     

Stimulus-dependent modulation of perceptual and motor learning in a serial reaction time task

In two experiments, we investigated the impact of spatial attributes on the representation acquired during a serial reaction time task. Two sequences were used, in which structural regularities occurred either in the horizontal or in the vertical locations of successive stimuli. After training with the dominant hand, participants were required to respond with the non-dominant hand to either the original sequence or to a mirror-ordered version of the original sequence that required finger movements homologous to those used during training. We observed that a difference in reaction times between the two transfer conditions was smaller in the vertical sequence than in the horizontal sequence. This pattern of results was independent of whether three fingers (Experiment 1) were used or only one finger (Experiment 2) was used for responding. This result suggests that perceptual and motor learning mechanisms may be weighted differently depending on the context in which the stimulus is presented.     

Kinesthetic Compensation for Sensorimotor Rearrangements

ABSTRACT

The authors report a new sensorimotor phenomenon in which participants use hand-sensed kinesthetic information to compensate for rotational sensorimotor rearrangements. This compensation benefits from conscious awareness and is related to hand posture. The technique can reduce control inefficiency with some misalignments by as much as 64%. The results support Y. Guiard's (1987) Guiard, Y. 1987. Asymmetric division of labor in human skilled bimanual action. Journal of Motor Behavior, 19: 486–517. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar] suggestion that in bimanual tasks one hand provides an operational frame of reference for the other hand as in a closed kinematic chain. Results with right-handed participants show that the right and left hands are equally effective at providing such a cue. A constant-angular-targeting-error model, similar to that used for hand movements by H. Cunningham and I. Vardi (1990) and for walking by S. K. Rushton, J. M. Harris, M. R. Lloyd, and J. P. Wann (1998), is used to model the trajectories of targeting hand movements demonstrating the phenomenon. The model provides a natural parameter of the error.     

Measurements of Muscular Strength,Endurance, and Recovery Over Fifteen Successive Days

Muscular output was measured in terms of strength, endurance, impulse, and recovery, with 10 Ss, 4 times per day over 15 successive days. A general index (the mean percentage of baseline performance with all measures) indicated that performance generally improved over the first 5 or 6 days, and remained relatively stable thereafter. The measures of strength were sensitive to within-day effects, whereas endurance and recovery measures were not influenced by such circadian rhythms.