Visual and tactile action effects determine bimanual coordination performance

Effect-based models of motor control assign a crucial role to anticipated perceptual feedback in action planning. Two experiments were conducted to test the validity of this proposal for discrete bimanual key press responses. The results revealed that the normally observed performance advantage for the preparation of two responses with homologous rather than non-homologous fingers becomes inverted when homologous fingers produce non-identical visual effects, and non-homologous fingers produce identical visual effects. In the second experiment the finger homology effect was strongly reduced when homologous fingers produced non-identical tactile feedback. The results show that representations of to-be-produced visual and tactile action effects both contribute to action planning, though possibly to a varying degree. Implications of these results for effect-based models of motor control are considered.     

On the timing basis of bimanual coordination in discrete and continuous tasks.

Motor events are behaviorally meaningful, discrete entities (e.g., key strokes) that are generated at some specific portion of an effector's movement trajectory. Bimanual coordination may be conceptualized with reference to such discrete motor events or with reference to continuous movement trajectories. Studies inspired by the former approach suggest that hand coordination is primarily achieved by assigning a coherent timing goal structure to the motor events produced by each hand. Studies conducted with the latter approach have shown that between-hand interdependence may also arise from the cross-coupling of the command signals that generate each hand's motion. Little is known, however, about the relationships between timing-level coordination and trajectory-level coordination of the hands. Some aspects of these relationships are analyzed using data from experiments that involved bimanual finger tapping and circle drawing at identical and different frequencies.     

Asynchrony in discrete bimanual aiming: Evidence for visual strategies of coordination

The bimanual coupling literature supposes an inherent drive for synchrony between the upper limbs when making discrete bimanual movements. The level of synchrony is argued to be task dependent, reliant on the visual demands of the two targets, and the result of a complex pattern of hand and eye movements (Bingham, Hughes, & Mon-Williams, 2008 ; Riek, Tresilian, Mon-Williams, Coppard, & Carson, 2003 ). However, recent work by Bruyn and Mason ( 2009 ) suggests that temporal coordination is not solely influenced by visual saccades. In this experimental series, a total of 8 participants performed congruent movements to targets either near or far from the midline. Targets far from the midline, requiring a visual saccade, resulted in greater terminal asynchrony. Initial and terminal asynchrony were not consistent, but linked to the task demands at that stage of the movement. If the asynchrony evident at the end of a bimanual movement is due to a complex pattern of hand and eye movements then the removal of visual feedback should result in an increase in synchrony. Sixteen participants then completed congruent and incongruent bimanual aiming movements to near and/or far targets. Movements were made with or without visual feedback of hands and targets. Analyses revealed that movements made without visual feedback showed increased synchrony between the limbs, yet movements to incongruent targets still showed greater asynchrony. We suggest that visual constraints are not the sole cause of asynchrony in discrete bimanual movements.     

Asynchrony in discrete bimanual aiming: Evidence for visual strategies of coordination

The bimanual coupling literature supposes an inherent drive for synchrony between the upper limbs when making discrete bimanual movements. The level of synchrony is argued to be task dependent, reliant on the visual demands of the two targets, and the result of a complex pattern of hand and eye movements (Bingham, Hughes, & Mon-Williams, 2008 Bingham, G. P., Hughes, K. and Mon-Williams, M. 2008. The coordination patterns observed when two hands reach-to-grasp separate objects. Experimental Brain Research, 184: 283–293. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]; Riek, Tresilian, Mon-Williams, Coppard, & Carson, 2003 Riek, S., Tresilian, J. R., Mon-Williams, M., Coppard, V. L. and Carson, R. G. 2003. Bimanual aiming and overt attention: One law for two hands. Experimental Brain Research, 153: 59–75. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). However, recent work by Bruyn and Mason (2009 Bruyn, J. L. and Mason, A. H. 2009. Temporal coordination during bimanual reach-to-grasp movements: The role of vision. The Quarterly Journal of Experimental Psychology, 62(7): 1328–1342. [Taylor & Francis Online] , [Google Scholar]) suggests that temporal coordination is not solely influenced by visual saccades. In this experimental series, a total of 8 participants performed congruent movements to targets either near or far from the midline. Targets far from the midline, requiring a visual saccade, resulted in greater terminal asynchrony. Initial and terminal asynchrony were not consistent, but linked to the task demands at that stage of the movement. If the asynchrony evident at the end of a bimanual movement is due to a complex pattern of hand and eye movements then the removal of visual feedback should result in an increase in synchrony. Sixteen participants then completed congruent and incongruent bimanual aiming movements to near and/or far targets. Movements were made with or without visual feedback of hands and targets. Analyses revealed that movements made without visual feedback showed increased synchrony between the limbs, yet movements to incongruent targets still showed greater asynchrony. We suggest that visual constraints are not the sole cause of asynchrony in discrete bimanual movements.     

Timing goals in bimanual coordination

Phase coupling between movement trajectories has been proposed as the basic mechanism of hand coordination in the production of bimanual rhythmic movements with a 1:2 frequency ratio. Here a central temporal coupling view is proposed as an alternative. Extending previous models of two-handed synchronic and alternate-hand tapping, we hypothesized that 1:2 tapping is performed under the control of a single internal timekeeper set at the frequency required for the fast hand. The fast hand is assumed to use every signal and the slow hand every other signal of the timekeeper, to produce actions coordinated in time. The model's predictions for the variance-covariance pattern of tap timing within and across hands were tested in an experiment that required tapping with both hands with 1:1 or 1:2 frequency ratio. The finger contact on the response plate was to be short or long, according to instruction. Prolonged finger contact entailed profound modifications in the movement trajectories but failed to modify the variance-covariance pattern of the tap timing. This pattern proved to conform to predictions under both the short and the long contact conditions, thus supporting the central temporal coupling hypothesis.     

Kinetic attraction during bimanual coordination

Two experiments examined the effects of independent variations in kinetic and kinematic requirements on interlimb coupling during a bimanual task. The goal of the investigation was to provide preliminary evidence regarding one general class of physical variables that constrains discrete bimanual movements. Subjects attempted to execute a smooth unidirectional movement with the left arm, along with a three-segment reversal movement with the right arm. The first experiment manipulated the torque required to produce the reversal action, while movement duration and average angular velocity were held constant for both limbs. Several indications of increased interlimb coupling, due to the kinetic variation, were evident. The converse manipulation was used in the second experiment, with movement time and kinematics (velocity, acceleration) changed independently of joint torque requirements for the reversal limb. No clear effect of kinematics on coupling strength was noted. The results suggest that one variable influencing interlimb attraction toward common spatiotemporal trajectories may be kinetic in nature.     

Perception-action coupling during bimanual coordination: the role of visual perception in the coalition of constraints that govern bimanual action

Constraints pertaining to interlimb coordination have been studied extensively in the past decades. In this debate, F. Mechsner (2004) has taken a provocative position by putting primary emphasis on perceptual principles that mediate coordinative stability. Whereas the present authors agree that the role of perceptual principles is of critical importance during coordination, they take issue with Mechsner's extreme position and with the evidence forwarded to support a purely perceptual-cognitive approach to bimanual coordination. More specifically, the authors emphasize that current knowledge about brain function argues against a dualism between perception and action, criticize the presented evidence that posture manipulations during coordination provide decisive evidence against motoric and muscular constraints, and report on potential pitfalls associated with the use of visual transformation procedures to support complex coordination patterns.     

Encoding and retrieval during bimanual rhythmic coordination

In 2 experiments, bimanual 1:1 rhythmic coordination was performed concurrently with encoding or retrieval of word lists. Effects of divided attention (DA) on coordination were indexed by changes in mean relative phase and recurrence measures of shared activity between the 2 limbs. Effects of DA on memory were indexed by deficits in recall relative to baseline. For DA at both encoding and retrieval, the equilibrium values of relative phase were shifted and the degree of shared activity between left and right rhythmic motions was reduced. Recall was reduced, however, only for DA at encoding. The results corroborate and extend those obtained with more conventional secondary tasks (e.g., visual reaction time), suggesting attention dissimilarities between episodic encoding and retrieval.     

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, despite similar demands placed on the coordination dynamics 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.     

Effects of task instructions and oscillation frequency on bimanual coordination

Increases in the oscillation frequency of bimanual movements produce a switch from an anti-phase (180° relative phase) to an in-phase (0° relative phase) coordination pattern. This finding is observed when subjects are instructed not to intervene when they feel themselves slipping out of the anti-phase pattern. The question addressed in this study concerned how performance would be affected if subjects were instructed to try to maintain the pattern at all times. This issue was addressed using two separate groups of subjects: one group was given the do not intervene instructions, the other group was told to try to stay with the pattern at all times. Forearm rotations were tested in 15 s trials, paced by an auditory metronome set at 1.0, 1.5, 2.0, 2.5, and 3.0 Hz. Frequency distributions of the point estimates of relative phase were analyzed. The Do not Intervene group replicated previous findings, as indicated by the development of a bimodal histogram of relative phase distributions with increases in oscillation frequency. However, a very different pattern of findings emerged with increases in oscillation frequency for the group told to stay with the anti-phase pattern. Rather than a bimodal distribution being developed, the data maintained 180° as its central tendency — no secondary distribution developed around 0° relative phase. These data suggest that volitional control can over-ride the inherent dynamical tendencies of the motor system.     

Effects of visual and auditory guidance on bimanual coordination complexity

Perceptual guidance of movement with simple visual or temporal information can facilitate performance of difficult coordination patterns. Guidance may override coordination constraints that usually limit stability of bimanual coordination to only in-phase and anti-phase. Movement dynamics, however, might not have the same characteristics with and without perceptual guidance. Do visual and auditory guidance produce qualitatively different dynamical organization of movement? An anti-phase wrist flexion and extension coordination task was performed under no specific perceptual guidance, under temporal guidance with a metronome, and under visual guidance with a Lissajous plot. For the time series of amplitudes, periods and relative phases, temporal correlations were measured with Detrended Fluctuation Analysis and complexity levels were measured with multiscale entropy. Temporal correlations of amplitudes and relative phases deviated from the typical 1/f variation towards more random variation under visual guidance. The same was observed for the series of periods under temporal guidance. Complexity levels for all time series were lower in visual guidance, but higher for periods under temporal guidance. Perceptual simplification of the task’s goal may produce enhancement of performance, but it is accompanied by changes in the details of movement organization that may be relevant to explain dependence and poor retention after practice under guidance.     

The interplay of attention and bimanual coordination dynamics

Despite their common origin, studies on motor coordination and on attentional load have developed into separate fields of investigation, bringing out findings, methods, and theories which are diverse if not mutually exclusive. Sitting at the intersection of these two fields, this article addresses the issue of behavioral flexibility by investigating how intention modifies the stability of existing patterns of coordination between moving limbs. It addresses the issue, largely ignored until now, of the attentional cost incurred by the central nervous system (CNS) in maintaining a coordination pattern at a given level of stability, in particular under different attentional priority requirements. The experimental paradigm adopted in these studies provides an original mix of a classical measure of attentional load, namely, reaction time, and of a dynamic approach to coordination, most suitable for characterizing the dynamic properties of coordinated behavior and behavioral change. Findings showed that central cost and pattern stability covary, suggesting that bimanual coordination and the attentional activity of the CNS involved in maintaining such a coordination bear on the same underlying dynamics. Such a conclusion provides a strong support to a unified approach to coordination encompassing a conceptualization in terms of information processing and another, more recent framework rooted in self-organization theories and dynamical systems models     

Perception and action in swimming: Effects of aquatic environment on upper limb inter-segmental coordination

This study assessed perception–action coupling in expert swimmers by focusing on their upper limb inter-segmental coordination in front crawl. To characterize this coupling, we manipulated the fluid flow and compared trials performed in a swimming pool and a swimming flume, both at a speed of 1.35 m s⁻¹. The temporal structure of the stroke cycle and the spatial coordination and its variability for both hand/lower arm and lower arm/upper arm couplings of the right body side were analyzed as a function of fluid flow using inertial sensors positioned on the corresponding segments. Swimmers’ perceptions in both environments were assessed using the Borg rating of perceived exertion scale. Results showed that manipulating the swimming environment impacts low-order (e.g., temporal, position, velocity or acceleration parameters) and high-order (i.e., spatial-temporal coordination) variables. The average stroke cycle duration and the relative duration of the catch and glide phases were reduced in the flume trial, which was perceived as very intense, whereas the pull and push phases were longer. Of the four coordination patterns (in-phase, anti-phase, proximal and distal: when the appropriate segment is leading the coordination of the other), flume swimming demonstrated more in-phase coordination for the catch and glide (between hand and lower arm) and recovery (hand/lower arm and lower arm/upper arm couplings). Conversely, the variability of the spatial coordination was not significantly different between the two environments, implying that expert swimmers maintain consistent and stable coordination despite constraints and whatever the swimming resistances. Investigations over a wider range of velocities are needed to better understand coordination dynamics when the aquatic environment is modified by a swimming flume. Since the design of flumes impacts significantly the hydrodynamics and turbulences of the fluid flow, previous results are mainly related to the characteristics of the flume used in the present study (or a similar one), and generalization is subject to additional investigations.     

Stabilisation of bimanual coordination through visual coupling

Eight right-handed participants performed a bilateral circle tracing task in symmetric or asymmetric patterns. Circle tracing was performed in synchrony with an auditory metronome and a visual display at, or comfortably below, each participant's transition frequency. The visual display consisted of a row of five light-emitting diodes (LEDs) arranged between the two circles (hands). Bimanual pattern stability was examined under conditions where the direction of illumination of the visual stimuli was compatible or incompatible with the hand direction. Symmetric patterns maintained stability for both movement rates whereas asymmetric patterns exhibited loss of stability at the transition frequency. Spontaneous reversals in circling direction occurred predominantly (94%) through the nondominant hand. Laterality effects were also evident in the aspect ratio (circularity of trajectories) and limb frequency variation, particularly in asymmetric patterns at the transition frequency. Compatibility between the stimulus direction and circling direction served to: stabilise symmetric patterns; stabilise asymmetric patterns by delaying the onset of transition; and stabilise the individual limb dynamics when the direction of the dominant side was compatible with the visual stimulus. The data from this multisegmental task lend support to a model of coupled oscillators whereby the coupling strength is anisotropic between the dominant and nondominant side, and lend further support for an account of manual asymmetries by way of a preferential perception–action coupling through the dominant limb. PsycINFO Classification: 2320     

Anchoring in a novel bimanual coordination pattern

Anchoring in cyclical movements has been defined as regions of reduced spatial or temporal variability [Beek, P. J. (1989). Juggling dynamics. PhD thesis. Amsterdam: Free University Press] that are typically found at movement reversal points. For in-phase and anti-phase movements, synchronizing reversal points with a metronome pulse has resulted in decreased anchor point variability and increased pattern stability [Byblow, W. D., Carson, R. G., & Goodman, D. (1994). Expressions of asymmetries and anchoring in bimanual coordination. Human Movement Science, 13, 3-28; Fink, P. W., Foo, P., Jirsa, V. K., & Kelso, J. A. S. (2000). Local and global stabilization of coordination by sensory information. Experimental Brain Research, 134, 9-20]. The present experiment examined anchoring during acquisition, retention, and transfer of a 90 degrees phase-offset continuous bimanual coordination pattern (whereby the right limb lags the left limb by one quarter cycle), involving horizontal flexion about the elbow. Three metronome synchronization strategies were imposed: participants either synchronized maximal flexion of the right arm (i.e., single metronome), both flexion and extension of the right arm (i.e., double metronome within-limb), or flexion of each arm (i.e., double metronome between-limb) to an auditory metronome. In contrast to simpler in-phase and anti-phase movements, synchronization of additional reversal points to the metronome did not reduce reversal point variability or increase pattern stability. Furthermore, practicing under different metronome synchronization strategies did not appear to have a significant effect on the rate of acquisition of the pattern.     

One-to-one and polyrhythmic temporal coordination in bimanual circle tracing

The authors manipulated movement amplitude in a bimanual circle-tracing task to alter the natural tracing frequency of the arms. Participants (N = 14) traced different-diameter circles simultaneously with the two arms in either in-phase (0 degrees) or antiphase (180 degrees) coordination, using the index fingers or plastic styli. Movement amplitude altered the natural tracing frequency of the arms, as demonstrated by the following 2 findings: (a) The larger the difference in circle diameter, the larger was the shift from the fixed-point values of 0 degrees and 180 degrees, and the shift increased as movement frequency increased. Those results are consistent with the manipulation of delta omega in the bimanual pendulum paradigm. (b) Increasing movement frequency induced transitions from 1:1 to non-1:1 coordination, contrary to findings in previous investigations of polyrhythmic coordination. Tactile feedback played a minimal role in stabilizing bimanual coordination in the current tasks.     

Deterministic variability and stability in detuned bimanual rhythmic coordination

We examined the effects of crossing different degrees of cooperation and competition on inphase and antiphase 1:1 frequency locked coordination of left- and right-hand-oscillated pendulums. Degree of cooperation was manipulated through the joint frequency of oscillation specified by a metronome (the higher the frequency, the weaker the cooperation), and degree of competition by length (and, therefore, preferred frequency) differences between the two pendulums (the greater the difference, the stronger the competition). Increasing competition was accompanied by either decreasing cooperation (for six participants) or increasing cooperation (for six different participants). On each trial, a participant attempted to produce a steady-state phase relation phi for a given combination of competition and cooperation. Numerical simulations of the extended Haken-Kelso-Bunz (HKB) equation were used to predict (a) the patterns of shift in phi from either 0 or pi radians due to the different competition-cooperation relations and (b) the patterns of variability in phi. It was expected that the HKB equation would be successful in respect to (a), which it was, but not in respect to (b). The observed failure to confirm (b) was expected from the variability due to the different nonharmonic dynamics of the component oscillators, a source of variability not included in the HKB equation. The experimental results together with simulations and analyses of the phase-plane trajectories of the component oscillators suggest the operation of deterministic in addition to stochastic variability in the phase relation of contralateral limbs.     

The effect of volition on the stability of bimanual coordination

The authors investigated how the intention to passively perform a behavior and the intention to persist with a behavior impact upon the spatial and temporal properties of bimanual coordination. Participants (N = 30) were asked to perform a bimanual coordination task that demanded the continuous rhythmic extension-flexion of the wrists. The frequency of movement was scaled by an auditory metronome beat from 1.5 Hz, increasing to 3.25 Hz in.25-Hz increments. The task was further defined by the requirement that the movements be performed initially in a prescribed pattern of coordination (in-phase or antiphase) while the participants assumed one of two different intentional states: stay with the prescribed pattern should it become unstable or do not intervene should the pattern begin to change. Transitions away from the initially prescribed pattern were observed only in trials conducted in the antiphase mode of coordination. The time at which the antiphase pattern of coordination became unstable was not found to be influenced by the intentional state. In addition, the do-not-intervene set led to a switch to an in-phase pattern of coordination whereas the stay set led to phase wandering. Those findings are discussed within the framework of a dynamic account of bimanual coordination.     

Goal congruency without stimulus congruency in bimanual coordination

Two experiments explored the role of stimulus congruency and goal congruency for the generation of object-oriented actions with two hands. Participants had to place two objects into either parallel or opposite orientations by carrying out either symmetrical or asymmetrical forearm rotations. Performance was superior when the required object orientations were identical rather than different, almost independent of the symmetry of the required arm movements. In extending previous research, goal congruency effects ensued even under conditions in which congruency of imperative response signals could not have contributed to goal congruency effects, either because only a single stimulus was used to indicate the required goals in an individual trial (Experiment 1) or such stimuli were absent at all (Experiment 2). The results thus confirm the importance of goal codes for the reconcilableness of bimanual actions, and rule out accounts in terms of stimulus-related processes.     

Anchoring strategies for learning a bimanual coordination pattern

Anchoring has been defined as synchronizing a point in a movement cycle with an external stimulus (W. D. Byblow, R. G. Carson, & D. Goodman, 1994). Previously, investigators have examined anchoring during in-phase and antiphase movements. The present authors examined anchoring during acquisition of a novel bimanual coordination pattern. Participants performed a 90 degrees pattern at 1 Hz, with a 2- or 4-Hz metronome. No group differences were found in pattern performance; however, the 4-Hz group developed more consistent anchoring relative to the metronome. Mechanical anchor-point variability differed by hand, position (midpoint vs. endpoint), and direction (flexion vs. extension) but not by metronome frequency. Those results support and extend previous findings but leave unanswered questions regarding the benefits and effectiveness of anchoring during a 90 degrees pattern.