Bimanual Finger Tapping: Effects of Frequency and Auditory Information on Timing Consistency and Coordination

The authors' goal in this study was to probe the basis for an earlier, unexpected finding that preferred-frequency finger tapping tends to have higher frequencies and to be less stable for in-phase than for antiphase tasks. In follow-up experiments, 3 protocols were employed: a preferred-frequency replication in both coordination modes, a metronome-driven matching of the preferred frequencies to each of the coordination modes, and a frequency scaling of both modes. The original findings were affirmed for preferred frequency. Tapping to a metronome had a differential effect on in-phase and antiphase: A more stable coupling across frequencies was exhibited during in-phase. Under frequency scaling, the antiphase pattern decomposed at lower frequencies than did in-phase, but no phase transitions were observed. The loss of stable coordination in both modes was attended by sudden increases in frequency differences between fingers and by phase wandering. The emergence of those effects is discussed in light of asymmetric modifications to the Haken-Kelso-Bunz model (H. Haken, J. A. S. Kelso, & H. Bunz, 1985) and the task constraints of tapping.     

A Direct-Learning Approach to Acquiring a Bimanual Tapping Skill

The theory of direct learning (D. M. Jacobs &; C. F. Michaels, 2007 Jacobs, D. M., &; Michaels, C. F. (2007). Direct learning. Ecological Psychology, 19, 321–349.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) has proven useful in understanding improvement in perception and exploratory action. Here the authors assess its usefulness for understanding the learning of a motor skill, bimanual tapping at a difficult phase relation. Twenty participants attempted to learn to tap with 2 index fingers at 2 Hz with a phase lag of 90° (i.e., with a right-right period of 500 ms and a right-left period of 125 ms). There were 30 trials, each with 50 tapping cycles. Computer-screen feedback informed of errors in both period and phase for each pair of taps. Participants differed dramatically in their success. Learning was assessed by identifying the succession of attractors capturing tapping over the experiment. A few participants’ attractors migrated from antiphase to 90° with an appropriate period; others became attracted to a fixed right-left interval, rather than phase, with or without attraction to period. Changes in attractor loci were explained with mixed success by direct learning, inviting elaboration of the theory. The transition to interval attractors was understood as a change in intention, and was remarkable for its indifference to typical bimanual interactions.     

Static and Phasic Cross-Talk Effects in Discrete Bimanual Reversal Movements

The authors examined the hypothesis that the phasic and the static cross-talk effects found in bimanual movements with different target amplitudes originate at different functional levels of motor control, which implies that the effects can be dissociated experimentally. When the difference between the short and the long amplitudes assigned to the 2 hands of 12 participants was decreased, the static effect disappeared. In contrast, the phasic effect, which can be observed only at short preparation intervals, did not disappear; although it became smaller in absolute terms, in relative terms it did not. In addition, the authors compared the time course of amplitude assimilation with the time course of amplitude variability and examined the correlation between left hand and right hand amplitudes. The disappearance of the phasic amplitude assimilation at increasing preparation intervals turned out to be delayed relative to the decline of the correlation between amplitudes. That finding suggests that the assimilation of mean amplitudes and the correlation between left hand and right hand amplitudes are not fully equivalent indicators of intermanual interactions, but may indicate different kinds of inter-limb coupling.     

The Representation of Action: Insights From Bimanual Coordination

ABSTRACT— The motor-program concept, emphasizing how actions are represented in the brain, helped bring the study of motor control into the realm of cognitive psychology. However, interest in representational issues was in limbo for much of the past 30 years, during which time the focus was on biomechanical and abstract accounts of the constraints underlying coordinated movement. We review recent behavioral and neuroscientific evidence that highlights multiple levels of constraints in bimanual coordination, with an emphasis on work demonstrating that a primary source of constraint arises from the manner in which action goals are represented.     

Development of Bimanual Skill: The Search for Stable Patterns of Coordination

In 2 experiments, dynamic systems theory predictions concerning intrinsic dynamics and variability of bimanual coordination were examined at different developmental stages. In Experiment 1, ten 4-, 6-, 7-, 8-, and 10-year-old children and adults performed unimanual dominant, unimanual nondominant, and bimanual continuous circle drawing. All tasks were performed at the participants' preferred rate, size, and mode of coordination. The 4-, 6-, and 7-year-old children produced larger circles with longer durations than those of the 8- and 10-year-olds and the adults. That finding demonstrates that younger children display different intrinsic dynamics than older children and adults. The 4-, 6-, and 7-year-old children also displayed more variability in bimanual coordination (more time in less stable patterns of coordination, higher standard deviation in relative phase) and produced more transitions between coordination patterns than the 8- and 10-year-olds and the adults. In Experiment 2, the same participants performed bimanual circles at increasing rates. Consistent with predictions of the HKB model (H. Haken, J. A. S. Kelso, & H. Bunz, 1985), the number of transitions decreased as speed increased. Some support was found for the notion that age-related variables of attention and rate contribute to the increased variability in young children's bimanual coordination.     

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.     

Spatial Conceptual Influences on the Coordination of Bimanual Actions: When a Dual Task Becomes a Single Task

When the left and right hands produce 2 different rhythms simultaneously, coordination of the hands is difficult unless the rhythms can be integrated into a unified temporal pattern. In the present study, the authors investigated whether a similar account can be applied to the spatial domain. Participants (N = 8) produced a movement trajectory of semicircular form in single-limb and bimanual conditions. In the bimanual tasks, 1 limb moved above the other in the frontal plane. Bimanual unified tasks were constructed so that the spatial paths to be produced by the 2 limbs could be easily conceptualized as parts of a unified circle pattern. Bimanual distinct tasks availed a less obvious spatial pattern that would unify the 2 tasks. Performance of the spatial patterns was more accurate in the unified task, despite similar demands placed on the coordination dynamics between the limbs in the 2 cases (e.g., the phase relations). The authors conclude that a dual task becomes a single task, and interlimb interference is reduced, when the spatial patterns produced by the 2 hands form a geometric arrangement that can be conceptualized as a unified representation.     

利手与语言功能偏侧化的遗传模型

利手与语言功能偏侧化现象不仅具有跨文化一致性和发生、发展上的关联性, 还具有明显的生态学优势, 从遗传角度探讨它们的成因是必要的。早期遗传模型认为, 存在一对等位基因分别决定左、右利手。当代单基因模型则将语言功能偏侧化也纳入进来, 认为等位基因不仅可以决定具有方向性的偏侧化, 而且可以使偏侧化有一定几率向左或向右。在这个框架下形成了方向-随机等位基因模型、X-连锁隐性基因模型和右侧位移理论, 它们对等位基因的位置和功能有不同表述, 对利手的划分标准、性别差异以及遗传和环境的关系也有不同阐释。今后需加强对语言偏侧化的数据验证, 进一步阐明语言感知、理解与利手的关系, 并注重基因怎样决定表型、基因多效性和多基因合作等问题的研究。     

Cortical Networks for Correcting Errors in Sensorimotor Synchronization Depend on the Direction of Asynchrony

Recent work provides clues that different cortical mechanisms may be employed when correcting for errors in sensorimotor synchronization that increase tap-tone asynchrony compared with those that decrease it. The authors tested this hypothesis by recording 64-channel electroencephalography while participants synchronized with an auditory metronome. We systematically introduced positive and negative phase-shift perturbations that were either liminal (10%) and subliminal (3%). We used a distributed source modeling approach to evaluate oscillatory activity and connectivity of discrete cortical sources. Three key findings support our hypothesis. First was a theta band response indicative of error detection and top-down control observed in frontomedial presupplementary motor area (pre-SMA) and anterior cingulate for liminal positive perturbations. Second was an increase in theta band coupling between the SMA and contralateral motor cortex exclusively for positive perturbations suggesting a top-down modulation of motor parameters. Third, when compared with other conditions, liminal positive perturbations result in an increase in postmovement beta rebound within contralateral primary motor cortex. The authors propose that frontomedial motor areas exert a top-down inhibitory influence over the primary motor cortex to effectively lengthen tap intervals in response to lengthening tap-tone asynchronies.     

Bimanual tapping of a syncopated rhythm reveals hemispheric preferences for relative movement frequencies

In bimanual multifrequency tapping, right-handers commonly use the right hand to tap the relatively higher rate and the left hand to tap the relatively lower rate. This could be due to hemispheric specializations for the processing of relative frequencies. An extension of the double-filtering-by-frequency theory to motor control proposes a left hemispheric specialization for the control of relatively high and a right hemispheric specialization for the control of relatively low tapping rates. We investigated timing variability and rhythmic accentuation in right handers tapping mono- and multifrequent bimanual rhythms to test the predictions of the double-filtering-by-frequency theory. Yet, hemispheric specializations for the processing of relative tapping rates could be masked by a left hemispheric dominance for the control of known sequences. Tapping was thus either performed in an overlearned quadruple meter (tap of the slow rhythm on the first auditory beat) or in a syncopated quadruple meter (tap of the slow rhythm on the fourth auditory beat). Independent of syncopation, the right hand outperformed the left hand in timing accuracy for fast tapping. A left hand timing benefit for slow tapping rates as predicted by the double-filtering-by-frequency theory was only found in the syncopated tapping group. This suggests a right hemisphere preference for the control of slow tapping rates when rhythms are not overlearned. Error rates indicate that overlearned rhythms represent hierarchically structured meters that are controlled by a single timer that could potentially reside in the left hemisphere.     

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.     

Effect of Object and Task Properties on Bimanual Transport

The use of both hands simultaneously when manipulating objects is fairly commonplace, but it is not known what factors encourage people to use two hands as opposed to one during simple tasks such as transport. In particular, we are interested in three possible transport strategies: unimanual transport, handing off between hands, and symmetric bimanual transport. In this study, we investigate the effect of object size, weight, and starting and ending position (configuration) as well as the need to balance the object on the use of these three strategies in a bowl-moving task. We find that configuration and balance have a strong effect on choice of strategy, and size and weight have a weaker effect. Hand-offs are most often used when the task requires moving an object from left to right and vice versa, while the unimanual strategy was frequently used when passing front to back. The bimanual strategy is only weakly affected by configuration. The need to balance an object causes subjects to favor unimanual and bimanual strategies over the hand-off. In addition, an analysis of transport duration and body rotation suggests that strategy choice may be driven by the desire to minimize body rotation.     

The Relationship of Target and Response Complexity in Coincident Timing Performance

This paper reports two experiments concerned with the interaction of response and target factors in a coincident timing situation. Coincident timing involves executing a response to intercept a moving target. The target response relationship was manipulated in the first experiment by providing some targets with no structure (linear path) and others containing 1 and 2 bounce points. In the second experiment, responses required 0, 1, or 2 reversals in direction. The results provide tentative support for the notion that structure in the target path could be linked to the key temporal response dynamics for improved performance consistency, and that subjects may alter their response structure to incorporate this linkage. This can be further extended to the advantage of simply moving while perceiving movement. This paper stresses the importance of examining the perceptual and motor requirements of the coincident timing skill in unison.     

Effects of Fencing Training on Motor Performance and Asymmetry Vary With Handedness

Abstract

Previous studies showed that motor asymmetries are reduced in left-handers and after a long-term fencing training in right-handers. Interestingly, left-handed athletes are substantially over-represented in elite fencing. These findings have been speculatively explained by imbalance in experience of fighting opposite handedness opponents resulted from skewed distribution of handedness, i.e. lefties encounter more righties than righties encounter lefties. Whereas these assumptions could be accurate, the underlying mechanisms remain ambiguous. In this study, we investigated effects of fencing training on motor performance and asymmetry with respect to handedness. We compared fencing performance of left- and right-handed fencers in both training and combat conditions. In the combat condition, left-handers won seven out of twelve matches consisted of twelve bouts each. They also showed a significantly longer hit detection time, a measure indicating better quality of fencing attack. In the training condition, left-handed fencers completed fencing board tests significantly faster than right-handers. These findings provide additional factor of superior motor performance to be considered when interpreting over-representation of lefties in elite fencing. Furthermore, our left-handers were less lateralized, which could explain that superior motor performance. This idea is consistent with previous findings of reduced asymmetry in right-handed fencers when comparing to non-athletes.     

Generation of Bimanual Trajectories of Disparate Eccentricity: Levels of Interference and Spontaneous Changes Over Practice

The authors examined intermanual interactions of 2 hands that were required to concurrently follow trajectories that differed in eccentricity. Ten healthy participants attempted to learn to trace 2 figures, a circle and an ellipse, with bilaterally isochronous (1:1) timing demands. Initial unimanual trials were followed by bilateral practice comprising 750 movement cycles. Two objectives were addressed: The authors' primary aim was to determine if kinematic interlimb interference is evident independent of spatial and temporal interference and to observe the potential practice-related changes in the nature of that interference. That test was afforded by participants' natural tendency to draw a circle with a relatively constant tangential velocity and an ellipse with a systematically varying velocity. A second aim was to observe the nature of spontaneous changes in the performance of each individual effector, and in the relationship between effectors, across practice. Those objectives were specifically addressed in a context in which augmented feedback was not available to direct the learners' attention to a particular feature of performance. The results suggested that interlimb assimilation of spatial features is the primary source of interference for that task and that apparent effects at the kinematic level are the secondary, indirect product of spatial coupling. Those results were found across blocks of practice. With respect to nondirected performance changes, substantially less improvement was evident in the performance of each individual effector than in the reduction of interlimb interference. Specifically, no practice-related changes in temporal variability or velocity bias, and minimal changes in trajectory smoothness, were evident in individual limbs. Conversely, significant reductions were observed in the variability of relative phase between limbs and in the magnitude of interlimb phase lag.     

Dynamics of 1:2 Coordination: Temporal Scaling,Latent 1:1, and Bistability

The simplest interlimb multifrequency coordination of 1:2 can be performed at different speeds and in at least two different styles or modes. The effects of speed and mode (in-phase or antiphase) were evaluated in a bimanual 1:2 rhythmic task in which participants (N = 8) oscillated hand-held pendulums with identical or different uncoupled frequencies. A motion equation in relative phase that captures the asymmetries of components and task predicted the 1:2 coordination equilibria resulting from temporal scaling. According to the experimental results, both coordination modes proved to be equally stable. More detailed analyses of individual trials showed signs that the more fundamental 1:1 coordination intruded into the 1:2 coordination.     

Limb Dominance and Its Effects on the Benefits of Intralimb Transfer of Learning: A Visuomotor Aiming Task

Research has attempted to address what characteristics benefit from transfer of learning; however, it is still unclear which characteristics are effector dependent or independent. Furthermore, it is not clear if intralimb transfer shows, similarly to interlimb transfer, an asymmetry of benefits between the upper limbs. The purpose of the current study is to examine if effector independence effects emerge, as observed in interlimb transfer studies, when transfer to new effector group within the same limb occurs, and whether the pattern of intralimb transfer benefits differ between the limbs. Our results suggest that a visuomotor task transfers within both limbs, even though the transfer benefits within the limbs seem to differ. This was supported by more transfer occurring in the dominant limb than the nondominant limb. Potential control mechanisms used for intralimb transfer are discussed.     

Interindividual Variability in Use-Dependent Plasticity Following Visuomotor Learning: The Effect of Handedness and Muscle Trained

Motor learning has been linked with increases in corticospinal excitability (CSE). However, the robustness of this link is unclear. In this study, changes in CSE associated with learning a visuomotor tracking task were mapped using transcranial magnetic stimulation (TMS). TMS maps were obtained before and after training with the first dorsal interosseous (FDI) of the dominant and nondominant hand, and for a distal (FDI) and proximal (biceps brachii) muscle. Tracking performance improved following 20 min of visuomotor training, while map area was unaffected. Large individual differences were observed with 18%–36% of the participants revealing an increase in TMS map area. This result highlights the complex relationship between motor learning and use-dependent plasticity of the motor cortex.     

Visual and Kinesthetic Components of Pursuit-Tracking Performance

Ss (N=75) were trained on a pursuit rotor for 10 trials with ambient illumination from a strobe light flashing at frequencies of either 2, 5, 10, 15, or 20/sec. A transfer trial followed, with a strobe flashing frequency of 10/sec for all Ss. Results supported hypotheses derived from Adams’ (1971) closed-loop theory of motor learning that (a) performance would improve during training as a function of amount of visual feedback available, and that (b) if after training visual feedback was reduced, performance would be maintained to the extent that reliance upon kinesthetic feedback had been learned as an alternate compensatory feedback loop.     

A Note on the Conscious Controls of Motor Units by Children Under Six

A simple form of training the conscious control of motor units in skeletal muscle has been demonstrated in a series of children under age 6. Easy boredom is the chief deterrent in the very young. So long as a child understands and cooperates, he can learn to isolate single units in a period of about 30 min.