Dynamic dominance persists during unsupported reaching

Previous studies examining lateralization of arm movements focused on supported movements in the horizontal plane, removing the effects of gravity. The authors hypothesized that interlimb differences in free reaching would be consistent with the differences shown during supported reaching. Kinematic and kinetic data were collected for the forearm and upper arm segments in a 3-direction reaching task. Results showed lateralization of coordination, reflected by initial movement direction and trajectory curvature. The nondominant arm showed increased initial direction errors, and path curvature associated with a timing deficit between elbow and shoulder peak torques. These coordination deficits did not disrupt final position accuracy. The authors conclude that nondominant arm coordination deficits are similar to those reported previously for horizontal plane movements.     

Serial-Position Effects in Motor Short-Term Memory

This study examined the effect of the length of a series of movements on the recall of those movements. Subjects (n =45) were randomly assigned to one of three experimental groups with each group recalling either three, six, or nine movements on a linear-slide apparatus. The subjects, while blindfolded, were presented with each movement by actively moving to a stop. Recall occurred 5 sec after the last movement to a stop on a trial. All subjects were given nine trials, each containing a different series of to-be-recalled movements. Results indicated that absolute error of recall of the three movements increased in a linear fashion. However, for six and nine movements, a bowing effect of the recall curve was noted following the fifth position. A primacy effect was more ‘ evident than was a recency effect. Accuracy of recall was a function of list length up to six movements, after which accuracy was not further impaired.     

Serial-position effects in motor short-term memory

This study examined the effect of the length of a series of movements on the recall of those movements. Subjects (n = 45) were randomly assigned to one of three experimental groups with each group recalling either three, six, or nine movements on a linear-slide apparatus. The subjects, while blindfolded, were presented with each movement by actively moving to a stop. Recall occurred 5 sec after the last movement to a stop on a trial. All subjects were given nine trials, each containing a different series of to-be-recalled movements. Results indicated that absolute error of recall of the three movements increased in a linear fashion. However, for six and nine movements, a bowing effect of the recall curve was noted following the fifth position. A primacy effect was more evident than was a recency effect. Accuracy of recall was a function of list length up to six movements, after which accuracy was not further impaired.     

Perception of movement patterns: tracking of movement

The tracking of complex two-dimensional movement patterns was studied. Subjects were blindfolded, and their right hand moved around stencil patterns in the midsagittal plane, while the left hand concurrently reproduced the right-hand movement. The accuracy with which the left hand shadowed the criterion movements of the right hand was measured in shape and size. Right-hand movements were active or passive. Present tracking performance was contrasted with errors in recall reported by Bairstow and Laszlo (1978). Results showed that tracking performance was accurate. Active and passive criterion movements were tracked differently. Tracking was clearly superior to recall performance.     

Lateralized regular spatial patterns in oscillating drawing arm movements of right-handed young women

There is a lacuna in literature with reference to the spatial lateral difference in fast rhythmical movements produced by the whole dominant and nondominant whole arm, where spinal regulation has a significant role. Based on a fast oscillating zigzag drawing task, this study focused on (a) creation of a specific model of the task based on the intermittencies of coupled vectors of the fast motion, (b) identification of the spatial patterns that triggered these vectors, and (c) identification of quantified lateral differences between the spatial rhythmical patterns. 12 strongly right-handed young women performed 9 to 11 trials drawing zigzag lines. Each participant was required to extend her arm and perform this task using the left and right arm selectively on a frontally positioned graphic design system. The spatial patterns produced on each trial were identified in terms of five constant combinations of horizontal (X) and vertical (Y) projections of each line on the zigzag drawings. The dominant arm differed from the nondominant arm in preferred patterns. Because the duration of each line in the zigzag was highly restricted in time, the appearance of the patterns with different block schemes of movement could be explained as being associated with lower levels of the central nervous system. Initiation of fast movement of the total upper arm is probably associated with selection of the block scheme of motor control appropriate to each arm. Each block scheme is grounded on the coupled vectors of motion organised with particular muscle groups. Some block schemes seemed linked specifically to the dominant arm.     

Control of interjoint coordination in the performance of manual circular movements can explain lateral specialization

Between-arm performance asymmetry can be seen in different arm movements requiring specific interjoint coordination to generate the desired hand trajectory. In the current investigation, we assessed between-arm asymmetry of shoulder-elbow coordination and its stability in the performance of circular movements. Participants were 16 healthy right-handed university students. The task consisted of performing cyclic circular movements with either the dominant right arm or the nondominant left arm at movement frequencies ranging from 40% of maximum to maximum frequency in steps of 15%. Kinematic analysis of shoulder and elbow motions was performed through an optoelectronic system in the three-dimensional space. Results showed that as movement frequency increased circularity of left arm movements diminished, taking an elliptical shape, becoming significantly different from the right arm at higher movement frequencies. Shoulder-elbow coordination was found to be asymmetric between the two arms across movement frequencies, with lower shoulder-elbow angle coefficients and higher relative phase for the left compared to the right arm. Results also revealed greater variability of left arm movements in all variables assessed, an outcome observed from low to high movement frequencies. From these findings, we propose that specialization of the left cerebral hemisphere for motor control resides in its higher capacity to generate appropriate and stable interjoint coordination leading to the planned hand trajectory.     

Aging and the restructuring of precued movements

A precue paradigm was used to examine the time it takes to restructure a planned motor response. Two groups of subjects, a young group and an elderly group, performed an aiming task in which 75% of the trials involved no change of movement parameters. On remaining trials, subjects had to change one or more of the movement parameters. Elderly subjects had slower reaction times (RTs), movement times, and made more errors in both conditions. Elderly subjects had proportionally longer RTs overall, independent of restructuring a movement plan. Preparation of arm and direction also exhibited a proportional increase in RT. However, differential aging effects were found for preparation of extent. Elderly subjects were slower preparing short movements compared with long movements, whereas young subjects showed the opposite trend. These results suggest that with advancing age, operations concerned with movement-plan restructuring for arm and direction undergo change in processing rate, whereas operations for extent undergo more extensive alteration.     

Effect of directional response variables on eye-hand reaction times and decision time

To determine if direction of response affects reaction time, we measured the time for hand response to a visual stimulus, using a sensitive, microprocessor-based testing device to determine simple reaction time (RT), choice RT, and decision time. Mean simple RT was 207 +/- 3.7 msec. (mean +/- SEM); mean choice RT was 268 +/- 4.2 msec; and mean decision time was 61 msec. No differences were noted for leftward versus rightward movements, or midline versus lateral movements. Choice RT increased by 1.49 msec./yr. of age. Simple RT increased significantly with age for the nondominant hand, but not for the dominant hand. Right-handed subjects were more rapid with the dominant hand for choice RT. We conclude that dominance of hand tested and test initiation mechanism have major effects, but direction of movement in the lateral plane has little effect on reaction time.     

The independence of recall and recognition in motor learning

A basic tenet of both current closed-loop theories of motor learning (Adams, 1971; Schmidt, 1975) is that the generation of response specifications during learning is required for the development of recall memory. Two experiments were performed to test this tenet by attempting to demonstrate the development of recall memory in the absence of response specification production. The task in both experiments required blindfolded subjects to learn to produce a rapid, novel criterion movement on a linear positioning device. Control subjects in both experiments actively produced movements during learning with knowledge of results (KR) while experimental subjects in Experiment 1 experienced only the endpoint locations and in Experiment 2 were passively moved to the endpoint locations. Following initial KR trials, both experimental and control groups attempted to actively produce the criterion movement in the absence of KR. The results of both experiments support closed-loop theory that active practice is required to develop recall memory. There was some suggestion, however, that passive experience with sensory feedback may also aid recall memory development, contrary to the two closed-loop theories.     

Encoding specificity principle in motor short-term memory for movement extent

The hypothesis was tested that, when the mode of presentation matches the mode of reproduction in memory for movement extent, there is less error in reproduction than when the modes are not matched. Female undergraduates (n = 24) were tested under active and passive criterion movements presented either under preselected or constrained conditions. All subjects underwent 36 trials involving the combination of three retention conditions (immediate, 20-sec unfilled, and 20-sec filled) and two reproduction conditions (active and passive). Results for absolute error showed that for constrained presentations, when the mode of presentation and the mode of reproduction were the same, accuracy was greater than when the modes of presentation and reproduction were different.     

Imagery ability and the acquisition and retention of movements

In this study, we examined the relationship between imagery ability, as measured by the Movement Imagery Questionnaire (MIQ), and the acquisition, retention, and reacquisition of movements. Based on their MIQ scores, 10 subjects were selected for the following imagery groups: high visual/high kinesthetic (HH), high visual/low kinesthetic (HL), and low visual/low kinesthetic (LL). The subjects learned four movements to a criterion level. Before each trial, subjects kinesthetically imaged the movement about to be produced. Following each acquisition trial, subjects were provided visual feedback. The acquisition phase was followed by a 2-day retention interval, a retention test consisting of three trials on each movement (no feedback provided), and a reacquisition phase. The HH group acquired the movements in the least number of trials, the LL group required the greatest number of trials, and the HL group required an intermediate number of trials. The data for the reacquisition phase showed the same trend. There was only weak evidence for a relationship between imagery ability and the retention of the movements. These findings support the position that high imagery ability facilitates the acquisition, but probably not the short term retention, of movements.     

Attention as a mediating variable in the dynamics of bimanual coordination

The influence of focal attention on the coordination dynamics in a bimanual circle drawing task was investigated. Six right-handed and seven left-handed subjects performed bimanual circling movements, in two modes of coordination, symmetrical or asymmetrical. The frequency of movement was scaled by an auditory metronome from 1.50 Hz to 3.00 Hz in 7 steps. On each trial, subjects were required to attend either to the dominant hand, to a neutral position, or to the nondominant hand.The uniformity of the relative tangential angle was lower in asymmetrical than in symmetrical conditions, but was not influenced by the direction of attention. In the asymmetrical mode, shifts in RTA relations, suggestive of loss of stability, were evident as the movement frequency was increased. Typically, these shifts were mediated by distortions of the trajectory of the nondominant limb. When the nondominant hand was the focus of attention, movements of this hand were more circular, and temporal variability was reduced, at the cost of a greater deviation from the target frequency. Movements of the dominant hand were not affected by the direction of attention. The findings show that although directed attention acts to modify the coordination dynamics, it does so primarily at the level of the individual hands, rather then in terms of the relation between them.     

Preparatory Set,Response Complexity,and Reaction Latency

The interaction between preparatory set and response complexity was demonstrated in an experiment investigating the reaction latency of discrete arm movements. Following simple finger-lift reaction-time (RT) trials, subjects performed simple and complex versions of a discrete horizontal arm movement under one of two enforced preparatory set conditions. For the simple task, requiring subjects to attend to the components of the response prior to stimulus presentation (enforced motor set) produced significantly shorter RTs than when concentration was on the stimulus (enforced sensory set). However, RT differences for the complex version of the task failed significance. Theoretical implications of the results for Henry’s (1960) memory drum theory of neuromotor reaction were discussed.     

Training for the production of novel timing movements: Contextual considerations

Summary The present study represented an attempt to determine the extent to which transfer performance on a novel timing task is influenced by contextual similarity (i.e., similar instructions, task requirements, etc.) between training and transfer phases of performance. All subjects were given trials on a task which involved a linear ballistic arm movement. The length of the movement was defined as the distance between a start button and a hinged target, which was knocked over by the subject at the end of the response. During training subjects attempted to produce their movements in a time of 550 ms and were given knowledge of results regarding timing error after each trial. During transfer trials a 300 ms movement time was attempted and no knowledge of results was given. Context was defined by the number of different movement distances performed during training and transfer. Half of the subjects received training trials with a single distance (constant context) while the other half received an equal number of trials with each of three distances (varied context). During the transfer stage of the experiment, subjects either performed in the same movement distance context experienced during training (i.e., constant to constant; varied to varied) or in the opposite context (i.e., constant to varied; varied to constant). The results of the transfer analysis suggested that similariy of context between training and transfer phases of performance was not crucial to the accurate production of a novel closed-timing movement. Implications of the present results for recent theories of memory development are discussed.     

Kinematic adaptations to perturbations as a function of practice in rhythmic drawing movements

Kinematic adaptations in multijoint rhythmic drawing movements were investigated under unexpected perturbations in friction levels between stylus and writing surface. Changes in coupling and stability properties were assessed as a function of practice level by applying perturbations to subjects' dominant and nondominant limbs. Under nonperturbation and perturbation conditions, joint motions of right-handed subjects were highly coupled in the nondominant limb and uncoupled in the dominant limb. Stability analyses of the kinematic responses in the phase plane showed a relatively higher intrajoint resistance to perturbations in the nondominant limb as compared to the dominant limb for the elbow joint. indicating a decrease in global joint stiffness with practice. These changes in joint coupling and stiffness with practice were not observed for left-handed subjects. In addition, the stability to perturbations in the end-effector (stylus) kinematics was related to the amount of joint coupling in the nondominant limb, whereas in the dominant limb there existed no such coupling. It was concluded that (a) practice changes the responses to perturbations from anatomically specific early in practice to task-specific late in practice, and (b) this shift is related to the stability in the joint phase-plane dynamics, degree of coupling between joint angles, and the decoupling of the dynamics in the intrinsic and extrinsic control spaces.     

Interference Between Location and Distance Information in Motor Short-Term Memory: The Respective Roles of Direct Kinesthetic Signals and Abstract Codes

Interference between location and distance information in motor short-term memory has been hypothesized on the basis of the systematic pattern of undershooting and overshooting in movement reproduction that occurs when the starting position for reproduction movements is shifted. To determine the possible contribution of limb-specific kinesthetic information to this systematic undershooting-overshooting pattern, we compared the reproduction of linear arm positioning movements performed under either same-limb or switched-limb conditions. Ten subjects were assigned to either a location or distance cue condition, and each subject completed a total of 40 trials, 20 under same-limb and 20 under switched-limb conditions. Each trial consisted of criterion and reproduction movements, separated by a 10-s retention interval. The starting position for the reproduction movement was shifted by 0, 2, or 4 cm in either direction from that of the criterion movement. The systematic undershooting-overshooting pattern, which occurs when either the movement location or distance is reproduced, arose under both the same-limb and switched-limb conditions, suggesting that the primary cause of the location-distance interference is not limb-specific kinesthetic information. Rather, more abstract information in the form of a conceptual memory code appears to be the probable cause of the location distance interference phenomenon.     

Interlimb differences in visuomotor and dynamic adaptation during targeted reaching in children

While a number of studies have focused on movement (a)symmetries between the arms in adults, less is known about movement asymmetries in typically developing children. The goal of this study was to examine interlimb differences in children when adapting to novel visuomotor and dynamic conditions while performing a center-out reaching task. We tested 13 right-handed children aged 9–11 years old. Prior to movement, one of eight targets arranged radially around the start position was randomly displayed. Movements were made either with the right (dominant) arm or the left (nondominant) arm. The children participated in two experiments separated by at least one week. In one experiment, subjects were exposed to a rotated visual display (30° about the start circle); and in the other, a 1 kg mass (attached eccentrically to the forearm axis). Each experiment consisted of three blocks: pre-exposure, exposure and post-exposure. Three measures of task performance were calculated from hand trajectory data: hand-path deviation from the straight target line, direction error at peak velocity and final position error. Results showed that during visuomotor adaptation, no interlimb differences were observed for any of the three measures. During dynamic adaptation, however, a significant difference between the arms was observed at the first cycle during dynamic adaptation. With regard to the aftereffects observed during the post-exposure block, direction error data indicate considerably large aftereffects for both arms during visuomotor adaptation; and there was a significant difference between the arms, resulting in substantially larger aftereffects for the right arm. Similarly, dynamic adaptation results also showed a significant difference between the arms; and post hoc analyses indicated that aftereffects were present only for the right arm. Collectively, these findings indicate that the dominant arm advantage for developing an internal model associated with a novel visuomotor or dynamic transform, as previously shown in young adults, may already be apparent at 9 to 11-year old children.     

An Informational Analysis of Active Kinesthesis as Measured by Amplitude of Movement

5 blindfolded Ss were required to make absolute judgments of the extent to which their extended right arm was voluntarily moved in the horizontal plane. The first experiment entailed the judgment of 20 different amplitudes and from these data a scale of equal discriminability was constructed for each S. From these individual scales amplitudes were selected for 5 additional absolute judgment experiments where the number of amplitudes were varied from 4 to 16. Analysis of the mean equal discriminability scale showed that kinesthetic sensitivity varied over the continuum of movements. The primary analysis of information transfer between number of amplitudes of movement and responses indicated that information transfer varied considerably over the 5 experiments with a maximum transfer of 2.48 bits occurring when 16 amplitudes were used. These results were discussed in terms of the possible cues involved in movement discrimination and whether kinesthetic cues could be used in a closed-loop model of voluntary movement control.     

Movement trajectory smoothness is not associated with the endpoint accuracy of rapid multi-joint arm movements in young and older adults

The minimum variance theory proposes that motor commands are corrupted by signal-dependent noise and smooth trajectories with low noise levels are selected to minimize endpoint error and endpoint variability. The purpose of the study was to determine the contribution of trajectory smoothness to the endpoint accuracy and endpoint variability of rapid multi-joint arm movements. Young and older adults performed arm movements (4 blocks of 25 trials) as fast and as accurately as possible to a target with the right (dominant) arm. Endpoint accuracy and endpoint variability along with trajectory smoothness and error were quantified for each block of trials. Endpoint error and endpoint variance were greater in older adults compared with young adults, but decreased at a similar rate with practice for the two age groups. The greater endpoint error and endpoint variance exhibited by older adults were primarily due to impairments in movement extent control and not movement direction control. The normalized jerk was similar for the two age groups, but was not strongly associated with endpoint error or endpoint variance for either group. However, endpoint variance was strongly associated with endpoint error for both the young and older adults. Finally, trajectory error was similar for both groups and was weakly associated with endpoint error for the older adults. The findings are not consistent with the predictions of the minimum variance theory, but support and extend previous observations that movement trajectories and endpoints are planned independently.     

Coding processes in preselected and constrained movements: effect of vision

Three experiments were conducted in which visual information was manipulated either at the endpoint or during preselected, subject defined and constrained, experimenter-defined movements. In Experiments 1 and 2 the subject's task was to reproduce the movement in the absence of vision. Augmenting the terminal location of the criterion movement with vision had no differential effect on reproduction in Experiment 1, although preselected movement accuracy was significantly superior to constrained. Providing vision throughout the criterion movement in Experiment 2 not only failed to improve the accuracy of constrained movements but decreased reproduction performance in preselected movements. In Experiment 3 procedures were adopted to control the allocation of the subjects' attention during the criterion movement. The subjects reproduced by vision alone, movement alone, or with both visual and movement information available. When subjects were informed of the modality of reproduction prior to criterion presentation, they were able to ignore concurrent input from vision and attend to movement information. In the absence of precues visual information was spontaneously attended. The data were interpreted as contrary to closed-loop assumptions that additional information necessarily enhances the strength of a motor memory representation. Rather, they can be accommodated in terms of Posner, Nissen and Klein's (1976) theoretical account of visual dominance and serve to illustrate the importance of selective attention effects in movement coding.