Changes in Saccadic and Manual Motor Control After Ocular Smooth Pursuit Adaptive Modifications

The gain of ocular smooth pursuit responses can be adaptively modified under certain circumstances. Evidence that these modifications are caused, at least partly, by changes at a sensory level comes from the fact that subsequent manual tracking movements generated during visual fixation are also modified in a similar manner. The question addressed in the present experiment was whether the modifications are constrained specifically to responses such as these, which are driven by retinal image motion, or whether they can also influence movements that make use of retinal image position. This was accomplished by comparing manual and oculomotor responses to step changes in target position before and after smooth pursuit adaptation. The results showed that, as with manual tracking movements, these responses were also modified by the adaptive procedure, although to a lesser extent. In particular, following a 20-min period in which subjects (N = 4) were submitted to a procedure designed to increase the gain of the smooth pursuit system, manual step tracking movements and ocular saccades displayed larger amplitudes than those shown prior to the adaptation. In addition, these gain changes were accompanied by appropriate alterations in response kinematics. Taken together, these results suggest that the mechanisms responsible for adaptive modifications in the smooth pursuit system are also able to more generally influence the processing of visuospatial information. The possible neurophysiological substrate underlying these mechanisms is discussed.     

The Role of Oculomotor Information in the Learning of Sequential Aiming Movements

With their eyes initially on either the home, midline, or final end position, 30 participants practiced a 2-target aiming movement. After 120 acquisition trials, participants performed a retention test and were then transferred to each of the other 2 eye conditions. During acquisition, all groups improved over practice, but the home group showed the greatest improvement. The temporal improvement was most pronounced in the times spent after peak velocity. Retention and transfer tests indicated that participants performed best under eye-movement conditions that were the same as the 1 they had practiced in. There was also positive transfer of training between conditions in which the oculomotor information was similar. Thus, to optimize learning, one should practice under the same afferent and oculomotor conditions that will be required for the final performance.     

Lifting weights in neonates: Developing visual control of reaching

To test whether newborn babies take account of external forces in moving their limbs, spontaneous arm-waving movements were measured while the baby lay supine with its head turned to one side. Free-hanging weights, attached to each wrist by strings passing over pulleys, pulled on the arms in the direction of the toes. The results showed the babies applied compensatory forces to keep the hand they faced moving in the same region. In contrast, the (invisible) contra-lateral hand was pulled down by the weights. In a second experiment, where the arms were occluded, both arms were pulled down, suggesting that sight of the arm was necessary in compensating for the weight. In a third, conclusive experiment the babies viewed the arm they were not facing on a small video-monitor and this time the babies kept the visible contra-lateral hand up despite the weights. The results challenge the general view that spontaneous arm movements of neonates are purposeless and either reflexive or due to spontaneous patterned efference to the muscles. Instead, the findings suggest that in waving their arms, neonates are developing visual control of reaching.     

Pursuit Rotor Reminiscence in Schizophrenics and Normals

Normal and schizophrenic Ss (N=24 each) did pursuit rotor tracking and reminiscence was the score of interest; rest pauses of 2, 12, and 30 min., and 1, 6, and 24 hr. were interpolated in counterbalanced order after 5 min. of practice. It was predicted, on the basis of previous work, that schizophrenics would show greater reminiscence after the longer rest pauses, normals after the shorter rest pauses. The expected cross-over effect was found, but at a non-significant level only. There were no order effects. A discussion is given of the relation of these results to the interpretation of schizophrenia in terms of ‘‘arousal.”     

Examining the Spatiotemporal Disruption to Gaze When Using a Myoelectric Prosthetic Hand

The aim of this study was to provide a detailed account of the spatial and temporal disruptions to eye-hand coordination when using a prosthetic hand during a sequential fine motor skill. Twenty-one able-bodied participants performed 15 trials of the picking up coins task derived from the Southampton Hand Assessment Procedure with their anatomic hand and with a prosthesis simulator while wearing eye-tracking equipment. Gaze behavior results revealed that when using the prosthesis, performance detriments were accompanied by significantly greater hand-focused gaze and a significantly longer time to disengage gaze from manipulations to plan upcoming movements. The study findings highlight key metrics that distinguish disruptions to eye-hand coordination that may have implications for the training of prosthesis use.     

The Effect of Remoteness on Intertrial Correlations in Pursuit Rotor Performance

120 male university students were tested on a Koerth pursuit rotor. One group of 60 Ss was tested on each of 6 days spaced throughout a 3-wk. period. Another group of 60 Ss performed the same task in an identical manner for test-retest days only, with the retest day following by 3 wk. One group had a large amount of practice while the other did not within a comparable time period. Each practice session consisted of 60 15-sec. trials. The effects of both practice and layoff on intertrial correlations separated by increasing remoteness was investigated. The findings indicated, as others have found, that correlations decrease in size as remoteness increases. Adjacent trial correlations were found to increase as practice increased.     

Some Physiological Concomitants of Pursuit Rotor Performance and Reminiscence

A frustration theory of pursuit rotor performance and reminiscence has previously been presented (Costello, 1967; Costello & Discipio, 1967). The theory was reformulated in terms of arousal theory and the following hypotheses were tested: (1) an inverted “U” relationship exists between level of arousal and performance level; (2) reminiscence results when S during the rest period moves closer to his optimum level of arousal; (3) massed practice produces a higher level of arousal than spaced practice; (4) experimental conditions producing a high drive state will also increase his arousal level. Findings in line with these hypotheses were found for EMG measures but not for GSR and pulse rate. In view of what appears to be the task-specific nature of the physiological results it was concluded that there was no particular advantage in reformulating the frustration theory in terms of arousal theory.     

Constraints on Arm Selection Processes When Reaching: Degrees of Freedom and Joint Amplitudes Interact to Influence Limb Selection

With an interest in identifying the variables that constrain arm choice when reaching, the authors had 11 right-handed participants perform free-choice and assigned-limb reaches at 9 object positions. The right arm was freely selected 100% of the time when reaching to positions at 30° and 40° into right hemispace. However, the left arm was freely selected to reach to positions at ?30° and ?40° in left hemispace 85% of the time. A comparison between free- and assigned-limb reaching kinematics revealed that free limb selection when reaching to the farthest positions was constrained by joint amplitude requirements and the time devoted to limb deceleration. Differences between free- and assigned-arm reaches were not evident when reaching to the midline and positions of ±10°, even though the right arm was freely selected most often for these positions. Different factors contribute to limb selection as a function of distance into a specific hemispace.     

The effects of the arm swing on biomechanical and physiological aspects of roller ski skating

This study analyzed the biomechanical and physiological effects of the arm swing in roller ski skating, and compared leg-skating (i.e. ski skating without poles) using a pronounced arm swing (SWING) with leg-skating using locked arms (LOCKED). Sixteen elite male cross-country skiers performed submaximal stages at 10, 15 and 20 km h⁻¹ on a 2% inclined treadmill in the two techniques. SWING demonstrated higher peak push-off forces and a higher force impulse at all speeds, but a longer cycle length only at the highest speed (all P < .05), indicating a lower force effectiveness with SWING at the two lowest speeds. Additionally, the flexion–extension movement in the lower limbs was more pronounced for SWING. Oxygen uptake was higher for SWING at the two lowest speeds (both P < .05) without any differences in blood lactate. At the highest speed, oxygen uptake did not differ between SWING and LOCKED, but the RER, blood lactate and ventilation were lower with SWING (all P < .05). Taken together, these results demonstrate that utilizing the arm swing in roller ski skating increases the ski forces and aerobic energy cost at low and moderate speeds, whereas the greater forces at high speed lead to a longer cycle length and smaller anaerobic contribution.     

Catching With Both Hands: An Evaluation of Neural Cross-Talk and Coordinative Structure Models of Bimanual Coordination

Kelso, Southard, and Goodman (1979) and Marteniuk and MacKenzie (1980) have each proposed a different theoretical model for bimanual coordination. In the model of Kelso et al., a close temporal relationship between the hands in a bimanual task is predicted, even when each hand is required to move different distances. In Marteniuk and MacKenzie's model, separate motor commands are issued so that each limb will arrive simultaneously at the specified movement endpoint, leading to low temporal associations between limbs. In most previous work on bimanual coordination, manual aiming tasks with differing constraints have been used by subjects in individual studies. In this study, the usefulness of existing models for predicting performance in a real-world catching task in which the required movement pattern was constrained by ball flight characteristics was examined. Eleven university students caught tennis balls with both hands in the following 3 conditions: Condition 1. Ball projected to the right shoulder area (left hand moved a greater distance than the right); Condition 2. Ball projected to center of the chest area, (both hands moved same distance); and Condition 3. Ball projected to left shoulder area (right hand moved a greater distance). Kinematic data (time to peak velocity, movement initiation time) indicating significant cross-correlations between the left and right limbs in all 3 conditions concurred with the data of Kelso et al. (1979) on manual aiming. Timing appeared to be an essential variable coordinating bimanual interceptive actions. Although the limbs moved at different speeds when each was required to move different distances, times to peak velocity showed strong associations, suggesting the presence of a coordinative structure.     

Developmental Characteristics of Disparate Bimanual Movement Skills in Typically Developing Children

Mastery of many tasks in daily life requires role differentiated bimanual hand use with high spatiotemporal cooperation and minimal interference. The authors investigated developmental changes in the performance of a disparate bimanual movement task requiring sequenced movements. Age groups were attributed to changes in CNS structures critical for bimanual control such as the corpus callosum (CC) and the prefrontal cortex; young children (5–6 years old), older children (7–9 years old), and adolescents (10–16 years old). Results show qualitative changes in spatiotemporal sequencing between the young and older children which typically marks a phase of distinct reduction of growth and myelination of the CC. Results show qualitative changes in spatiotemporal sequencing between the young and older children, which coincides with distinct changes in the growth rate and myelination of the CC. The results further support the hypothesis that CC maturation plays an important role in the development of bimanual skills.     

Muscle Strength Training Alters Muscle Activation of the Lower Extremity during Side-Step Cutting in Females

Abstract

The objective of this study was to examine the effects of muscle strength training on knee kinematics/kinetics and muscle activation patterns during anticipated side-step cutting. Three-dimensional knee kinematics/kinetics data and muscle activation of selected lower extremity muscles were measured while performing cutting before and after completing 10-week circuit strength training mixed typical resistance training and power training (intervention) or no training (control) from 25 female subjects. The muscle strength of quadriceps and hamstrings were measured before and after training using isokinetic dynamometer. No statistically significant differences were observed in quadriceps and hamstrings muscle strength, all kinematic/kinetic variables, and muscle activation for the control group. Both quadriceps (p?=?0.005) and hamstrings (p?=?0.030) muscle strength were increased after training. An increased biceps femoris (p?=?0.003) and H:Q ratio of activation (p?=?0.016), as well as decreased gastrocnemius muscle activation (p?=?0.012) during pre-activation phase in intervention group were found. No significant differences were found in knee kinematics and kinetics both at the time frame of the initial contact and the peak tibial anterior shear force after training. In conclusion, muscle strength training altered some muscle activations of lower extremity muscles, which might affect the risk of ACL injury, but it did not change the kinematic/kinetic parameters.     

The relationship between reward and probability: Evidence that exploration may be intrinsically rewarding

ABSTRACT

The probability of an event occurring and the reward associated with the event can both modulate behaviour. Response times are decreased to stimuli that are either more rewarding or more likely. These two factors can be combined to give an Expected Value (EV) associated with the event (i.e., probability of the event x reward magnitude). In four experiments we investigate the effect of reward and probability on both saccadic and manual responses. When tested separately we find evidence for both a reward and probability effect across response types. When manipulations of reward magnitude and probability of the event were combined, the probability modulations dominated and these data were not well accounted for by the EV. However, a post-hoc model that included an additional intrinsic reward associated with responding provided an excellent account for the data. We argue that reward consists of both an explicit and intrinsic component. In our task, the saccadic and manual responses are linked to the information provided by the targets and the goals of the task, and successful completion of these is in itself rewarding. As a result, targets associated with a higher probability of being presented have a higher intrinsic reward.     

The Pursuit of Epistemic Good

Pace Zagzebski, there is no route from the value of knowledge to a non–reliabilist virtue–theoretic epistemology. Her discussion of the value problem is marred by an uncritical and confused employment of the notion of a "state" of knowledge, an uncritical acceptance of a "knowledge–belief" identity thesis, and an incoherent presumption that the widely held thought that knowledge is more valuable than true belief amounts to the view that knowledge is a state of true belief having an intrinsic property which a state of 'mere" true belief lacks. Her arguments against a "machine–product" conception of knowledge are undermined by these flaws, while the alternative "agent–act" model she recommends is unattractive, at odds with the knowledge–belief identity thesis she favours, and no solution to the problem of the value of knowledge she poses. I end with the observation that her version of virtue–theoretic epistemology points in the direction of cognitive decision–theoretic norms, and I briefly discuss the bearing of this fact upon her viewpoint.     

The Pursuit of Epistemic Good

Pace Zagzebski, there is no route from the value of knowledge to a non–reliabilist virtue–theoretic epistemology. Her discussion of the value problem is marred by an uncritical and confused employment of the notion of a "state" of knowledge, an uncritical acceptance of a "knowledge–belief" identity thesis, and an incoherent presumption that the widely held thought that knowledge is more valuable than true belief amounts to the view that knowledge is a state of true belief having an intrinsic property which a state of 'mere" true belief lacks. Her arguments against a "machine–product" conception of knowledge are undermined by these flaws, while the alternative "agent–act" model she recommends is unattractive, at odds with the knowledge–belief identity thesis she favours, and no solution to the problem of the value of knowledge she poses. I end with the observation that her version of virtue–theoretic epistemology points in the direction of cognitive decision–theoretic norms, and I briefly discuss the bearing of this fact upon her viewpoint.     

Gross Motor Performance in Minimally Brain Injured Children

As a pre-requisite to curriculum development, the characteristics of the gross motor performance of special education classes of minimally brain injured boys and girls were described. In general, age changes in mean performance were linear, the scores of the boys being the superior. The level of performance very closely resembled that of comparison groups of educable mentally retarded children from the same school districts.     

E-Z阅读者模型的新进展

该文介绍了以序列加工假设为基础的眼动控制模型——E-Z阅读者模型的基本内容和最新进展(模型6-9)。新的E-Z阅读者模型可以有效解释阅读过程中认知加工的眼动控制机制。随着研究的深入,E-Z阅读者模型的结构不断发展完善,而且还促进了许多新的眼动研究。     

诺贝尔科学奖与日本人的追求

诺贝尔科学奖是世界上对科学工作者最崇高、重要的奖励。事实证明,颁发此奖极有利于促进科学事业的发展。日本由技术革新到科学革新的变革,进而在新世纪的几年里连续获得诺贝尔奖,也说明科学创新的重要。