Auditory information is beneficial for adults with Down syndrome in a continuous bimanual task

Much recent research using discrete unimanual tasks has indicated that individuals with Down syndrome (DS) have more difficulty performing verbal-motor tasks as compared to visual-motor tasks (see Perceptual-Motor Behavior in Down Syndrome, Human Kinetics, Champaign, IL, 2000, p. 305 for a review). In continuous tasks, however, individuals with DS perform better when movement is guided by auditory information compared to visual information (Downs Syndr.: Res. Prac. 4 (1996) 25; J. Sport Exercise Psy. 22 (2000) S90). The aim of the present study was to investigate if there are any differences for adults with DS between visual, auditory and verbal guidance in a continuous bimanual task. Ten adults with DS, 10 adults without DS and 10 typically developing children drew lines bimanually towards the body (down) and away from the body (up) following three different guidance conditions: visual (flashing line), auditory (high tone, low tone), and verbal (“up”, “down”). All participants produced mostly in-phase movements and were close to the 1000 ms target time for all guidance conditions. The adults with DS, however, displayed greater variability in their movement time, movement amplitude and bimanual coordination than adults without DS. For all groups, the left hand was slower and more variable in producing the lateral movements than the right hand. The results regarding guidance information suggest that auditory information is beneficial for repetitive bimanual tasks for adults with DS. Possible mechanisms that cause these results will be discussed.     

Auditory instructional cues benefit unimanual and bimanual drawing in Parkinson's disease patients

The present study investigated performance of unimanual and bimanual anti-phase and in-phase upper limb line drawing using three different types of cues. Fifteen Parkinson’s disease (PD) patients, 15 elderly, and 15 young adults drew lines away from and towards their body on a tabletop every 1000 ms for 30 s under three different cueing conditions: (1) verbal (‘up’, ‘down’); (2) auditory (high tone, low tone); (3) visual (target line switched from top to bottom). PD patients had larger and more variable amplitudes which may be related to the finding that they also produced more curvilinear movements than young and elderly adults. Consistent with previous research, when compared to the elderly and young adult group PD patients produced a mean relative phase which deviated more from the instructed coordination modes and they showed larger variability of relative phase in bimanual coordination, especially in anti-phase conditions. For all groups, auditory and verbal cues resulted in lower coefficient of variance of cycle time, lower variability of amplitude and lower variability of relative phase than visual cues. The benefit of auditory cues may be related to the timing nature of the task or factors related to the auditory cues (e.g., reduced attentional demands, more kinesthetic focus).     

Effects of S-R and R-R compatibility on bimanual movement time

Bimanual asymmetrical movements are generally found to be slower than symmetrical movements but asymmetrical movement normally involves visual separation of targets which might account for the effect. By using a system in which the subject controls two cursors on an oscilloscope screen by moving two levers the S-R relationship on either hand can be reversed, thus providing an asymmetrical movement task without visual separation of targets. Movement times for five right-handed subjects were recorded on four unimanual and six bimanual conditions varying with respect to both S-R and R-R compatibility. In the unimanual conditions, the left hand was found to be as fast as the right when the opposite S-R relationship was used. In the bimanual tasks visual separation of targets was a relatively minor factor movement time being strongly influenced by S-R compatibility and to a lesser degree by R-R compatibility. The results suggest that compatibility, rather than being a property of a single central channel, differs, as between the two cerebral hemispheres.     

Performance of unimanual and bimanual multiphased prehensile movements

By manipulating task action demands in 2 experiments, the author investigated whether the context-dependent effects seen in unimanual multiphase movements are also present in bimanual movements. Participants (N = 14) in Experiment 1 either placed or tossed objects into targets. The results indicated that the intention to perform a subsequent action with an object could influence the performance of an earlier movement in a sequence in both unimanual and bimanual tasks. Furthermore, assimilation effects were found when the subsequent tasks being performed by the 2 hands were incongruent. In Experiment 2, the author investigated in 12 participants whether planning in a multiphase movement includes some representation of the accuracy demands of the subsequent task. The accuracy demands of a subsequent task did not appear to influence initial movement planning. Instead, the present results support the notion that it is the action requirements of the subsequent movement that lead to context-dependent effects.     

Asymmetries in Coupling Dynamics of Perception and Action

The influence of information-based dynamics on coordination dynamics of rhythmic movement was examined with special reference to the expression of asymmetries. In Experiment 1, right-handed subjects performed unimanual, rhythmical movements in coordination with either a discrete or continuous visual display. The right hand-visual display system defined a more stable perception-action collective than the left, particularly when continuous visual information was available. In Experiment 2, the same subjects performed rhythmic bimanual movements in coordination with a continuous visual display. The action collective was inherently more stable than the perception-action collective, although similar patterns were observed at both levels. Importantly, the dynamics of the perception-action collective impinged upon the dynamics of the action collective in terms of stability. Asymmetries remained evident between limbs in the bimanual preparations, with the left hand exhibiting greater limit-cycle variability and also a tendency to more often effect transitions at the action couple. Features of dynamical models that capture characteristics of manual asymmetries are discussed.     

Coordination dynamics and attentional costs of continuous and discontinuous bimanual circle drawing movements

It has been suggested that the temporal control of rhythmic unimanual movements is different between tasks requiring continuous (e.g., circle drawing) and discontinuous movements (e.g., finger tapping). Specifically, for continuous movements temporal regularities are an emergent property, whereas for tasks that involve discontinuities timing is an explicit part of the action goal. The present experiment further investigated the control of continuous and discontinuous movements by comparing the coordination dynamics and attentional demands of bimanual continuous circle drawing with bimanual intermittent circle drawing. The intermittent task required participants to insert a 400ms pause between each cycle while circling. Using dual-task methodology, 15 right-handed participants performed the two circle drawing tasks, while vocally responding to randomly presented auditory probes. The circle drawing tasks were performed in symmetrical and asymmetrical coordination modes and at movement frequencies of 1Hz and 1.7Hz. Intermittent circle drawing exhibited superior spatial and temporal accuracy and stability than continuous circle drawing supporting the hypothesis that the two tasks have different underlying control processes. In terms of attentional cost, probe RT was significantly slower during the intermittent circle drawing task than the continuous circle drawing task across both coordination modes and movement frequencies. Of interest was the finding that in the intermittent circling task reaction time (RT) to probes presented during the pause between cycles did not differ from the RT to probes occurring during the circling movement. The differences in attentional demands between the intermittent and continuous circle drawing tasks may reflect the operation of explicit event timing and implicit emergent timing processes, respectively.     

Interlimb coordination following stroke

Studies investigating whether simultaneous bilateral movements can facilitate performance of the impaired limb(s) of stroke patients have returned mixed results. In the present study we compared unilateral limb performance (amplitude, cycle duration) with performance during an interlimb coordination task involving both homologous (both arms, both legs) and non-homologous (one arm, one leg) limbs in stroke participants (n=7) and healthy age-matched controls (n=7). In addition, the effect of on-line augmented visual feedback on interlimb coordination was investigated. Participants performed cyclical flexion-extension movements of the arms and legs in the sagittal plane paced by an auditory metronome (1 Hz). Movement amplitudes were larger and cycle durations shorter during homologous limb coordination than non-homologous coordination. Compared with unilateral movements both groups had reduced movement amplitudes and the stroke group increased cycle duration when interlimb coordination tasks were performed. These effects were most evident during non-homologous (arm and leg) coordination. No evidence of facilitation of the impaired limb(s) was found in any of the interlimb coordination conditions. Augmented visual feedback had minimal effect on the movements of control participants but lead to an increase of cycle duration for stroke participants.     

Intermovement interval and spatial assimilation effects in sequential bimanual and unimanual movements

This study extended earlier work by showing spatial assimilations in sequential bimanual and unimanual movements separated by 1.5-3.5 s. In Experiments 1 and 2, 30 right-handed participants (18-22 years of age) made rapid single and bimanual lever reversals of 20 degrees and 60 degrees assigned to 1.5, 2.5, or 3.5 s intermovement interval groups. Participants self-timed the intermovement interval in the first experiment, but it was provided in the second experiment using separate auditory stimuli. In the third experiment, participants performed both the 20 degree and 60 degree movement with the same hand. In all experiments, the shorter-distance limb overshot and the longer-distance limb undershot the targets in both bimanual and unimanual sequential movements relative to single movements in all three intermovement interval groups, particularly in the non-dominant left limb. The results suggest that assimilation effects in sequential movements are caused by command interactions at the planning level, but the effects are reduced by practice.     

Specification of movement amplitudes for the left and right hands: evidence for transient parametric coupling from overlapping-task performance

Bimanual coordination tasks suggest transient cross-talk between concurrent specification processes for movements of the left and right hand that vanishes as the time for specification increases. In 2 experiments with overlapping and successive unimanual tasks, the hypothesis of transient coupling was examined for a psychological-refractory-period paradigm. Time for specification was manipulated by varying the delay between first and second signal (Experiment 1) and by precuing the first response (Experiment 2). Participants performed rapid reversal movements of same or different amplitudes with the left and right hands. With different amplitudes, reaction times (RTs) of the second responses were longer than with same amplitudes at short delays, and this disappeared at longer delays in Experiment 1. In Experiment 2, precuing also reduced the difference between RTs of second responses in same-amplitude and different-amplitude trials. These findings are consistent with the hypothesis of transient coupling during amplitude specification obtained with bimanual tasks.     

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.     

Period Duration of Physical and Im aginary Movement Sequences Affects Contralateral Amplitude Modulation

The hypothesis was tested that the strength of cross-manual effects of voluntary amplitude modulations in bimanual tasks increases when less preparation time is available during the execution of a sequence of movements. By means of the continuation procedure, various period durations (600, 800, 1200, and 1800 msec) of movement sequences were imposed. Subjects performed bimanual periodic arm movements on two digitizers: constant-amplitude movements (short or long) with the one hand, and movements of constant short or constant long amplitudes and movements of alternating short and long amplitudes with the other hand. Period-duration-dependent modulations of the amplitude were observed in movements of instructed constant amplitudes when the other hand performed alternating-amplitude movements, but not when the other hand performed constant-amplitude movements. Not only physical performance, but also the imaginary production of alternating-amplitude movements resulted in period-duration-dependent cross-manual effects, though reduced in size. The pattern of results is in agreement with a recently proposed two-level model of cross-manual effects according to which cross-talk can occur at the programming level as well as at the execution level.     

Unimanual and bimanual tasks and the assessment of handedness in toddlers

The goal of this study was to examine the relations between three different measures of handedness: unimanual reaching, bimanual manipulation and unimanual manipulation. The appropriateness of the task chosen to evaluate handedness was also explored by contrasting different bimanual manipulation tasks for the more or less differentiated (passive\active) roles assigned to each hand. Forty children, between 18 and 36 months of age, were tested in the three conditions. The results show that the degree of bimanual handedness is greater on the bimanual tasks with a strong role differentiation than on the tasks with less differentiation. Bimanual tasks with a strong role differentiation elicited more right‐handedness than unimanual reaching. Among the children who showed handedness in reaching, the correlation between unimanual and bimanual handedness was high, especially for right‐handers. For some tasks, bimanual handedness appeared at the earliest age studied here (18 months), and there was little relationship between bimanual handedness and bimanual skill. In contrast with unimanual reaching, there was no age‐related change in the degree of handedness for either bimanual or unimanual manipulation. There was a bias toward the use of the right hand for unimanual manipulation. It was concluded that grasping is not the best task to employ to look for robust evidence of handedness, and that bimanual tasks offer a better way to estimate handedness in children, as long as the tasks are carefully chosen.     

Analytical Inverse Optimization in Two-Hand Prehensile Tasks

The authors explored application of analytical inverse optimization (ANIO) method to the normal finger forces in unimanual and bimanual prehensile tasks with discrete and continuously changing constraints. The subjects held an instrumented handle vertically with one or two hands. The external torque and grip force changed across trials or within a trial continuously. Principal component analysis showed similar percentages of variance accounted for by the first two principal components across tasks and conditions. Compared to unimanual tasks, bimanual tasks showed significantly more frequent inability to find a cost function leading to a stable solution. In cases of stable solutions, similar second-order polynomials were computed as cost functions across tasks and condition. The bimanual tasks, however, showed significantly worse goodness-of-fit index values. The authors show that ANIO can be used in tasks with slowly changing constraints making it an attractive tool to study optimality of performance in special populations. They also show that ANIO can fail in multifinger tasks, likely due to irreproducible behavior across trials, more likely to happen in bimanual tasks compared to unimanual tasks.     

The production of bimanual percussion in 12- to 24-month-old children

Bimanual coordination represents a complex self-organizing system that is subject to both internal and contextual constraints. Although there has been interest in examining bimanual development throughout the lifespan, few data exist relative to the bimanual activity of children between 1 and 4 years of age. The study reported here represents an initial effort to address this gap. Twenty-seven children who were either 12, 18 or 24 months old were videotaped while drumming with sticks on a plastic drum. Two independent observers recorded bout length as well as number and phase relation of movement cycles within bouts. Kinematic analysis provided more detailed information about the timing and form of children's activity. Results indicate that bimanual drumming becomes preferred over unimanual drumming by 2 years of age, that the proportions of different phase relations exhibited by children change between 1 and 2 years of age, and that the behavior appears to go through periods of stability and variability within this age range. These results are discussed in the context of the child's physical development and interactions with the environment during this period.     

Motor planning and execution in left- and right-handed individuals during a bimanual grasping and placing task

The issue of handedness has been the topic of great interest for researchers in a number of scientific domains. It is typically observed that the dominant hand yields numerous behavioral advantages over the non-dominant hand during unimanual tasks, which provides evidence of hemispheric specialization. In contrast to advantages for the dominant hand during motor execution, recent research has demonstrated that the right hand has advantages during motor planning (regardless of handedness), indicating that motor planning is a specialized function of the left hemisphere. In the present study we explored hemispheric advantages in motor planning and execution in left- and right-handed individuals during a bimanual grasping and placing task. Replicating previous findings, both motor planning and execution was influenced by object end-orientation congruency. In addition, although motor planning (i.e., end-state comfort) was not influenced by hand or handedness, motor execution differed between left and right hand, with shorter object transport times observed for the left hand, regardless of handedness. These results demonstrate that the hemispheric advantages often observed in unimanual tasks do not extend to discrete bimanual tasks. We propose that the differences in object transport time between the two hands arise from overt shifting visual fixation between the two hands/objects.     

Impact of Handedness Consistency on Bimanual and Unimanual Continuous Movements

Bimanual coordination is an essential human function requiring efficient interhemispheric communication to produce coordinated movements. Previous research suggests a “bimanual advantage” phenomenon, where completing synchronized bimanual tasks results in less variability than unimanual tasks. Additionally, of hand dominance has been shown to influence coordinated performance. The present study examined the bimanual advantage in individuals with consistent and inconsistent handedness. It was predicted that participants with consistent handedness would not display a bimanual advantage unlike those with inconsistent handedness. Fifty-six young adults completed a finger-tapping paradigm in five conditions: unimanual tapping with either left or right hand, in-phase bimanual tapping, and out-of phase bimanual tapping led by either left or right hand. Results were not consistent with the hypothesis that participants with consistent handedness displayed the “bimanual advantage”. However, the “bimanual advantage” was not evident for the inconsistent handers when the temporal consistency was measured with either the left or right hand only. Overall, the “bimanual advantage” may be dependent upon consistency of hand preference, as well as the direction of hand dominance.     

Structural constraints on bimanual movements

Summary A theoretical framework is outlined, according to which structural constraints on bimanual movements can at least in part be understood as coupling between parameters of generalized motor programs. This framework provides a conceptual link between reaction-time data from experiments with bimanual responses, successive unimanual responses, and choice between left-hand and right-hand responses on the one hand and performance data obtained with concurrently performed continuous movements or sequences of discrete responses on the other. On the basis of data obtained with different methods for the study of intermanual interactions, a distinction is drawn between steady-state and transient constraints, and the hypothesis that the tendency to coactivate homologous muscles originates from a transient coupling of program parameters is applied to a variety of observations on performance in different tasks. Finally, the notion of transient constraints is applied to other types of intermanual interdependencies and to interpersonal coordination; the possible emergence of transient constraints from steady-state constraints through progressive development of inhibitory pathways in childhood is discussed, as is the potential biological significance of transient constraints.Part of the work reported in this paper was done while I enjoyed the hospitality on the NIAS, Wassenaar (NL)     

Bimanual interference associated with the selection of target locations

Four experiments were conducted to identify the locus of interference observed during the preparation of bimanual reaching movements. Target locations were specified by color, and the right-hand and left-hand targets could be either the same or a different color. Movements of different amplitudes (Experiment 1) or different directions (Experiment 2) to targets of the same color were initiated more quickly than symmetric movements to targets of different colors. These results indicate that costs observed during bimanual movements arise during target selection rather than during motor programming. Experiments 3 and 4 further examined the interference associated with target selection. Reaction time costs were found with unimanual movements when the target was presented among distractors associated with responses for the other hand. Interference observed during bimanual reaching appears to reflect difficulty in segregating the response rules assigned to each hand.     

Kinematic parameters of hand movement during a disparate bimanual movement task in children with unilateral Cerebral Palsy

Children with unilateral Cerebral Palsy (uCP) experience problems performing tasks requiring the coordinated use of both hands (bimanual coordination; BC). Additionally, some children with uCP display involuntary symmetrical activation of the opposing hand (mirrored movements). Measures, used to investigate therapy-related improvements focus on the functionality of the affected hand during unimanual or bimanual tasks. None however specifically address spatiotemporal integration of both hands. We explored the kinematics of hand movements during a bimanual task to identify parameters of BC. Thirty-seven children (aged 10.9 ± 2.6 years, 20 male) diagnosed with uCP participated. 3D kinematic motion analysis was performed during the task requiring opening of a box with their affected- (AH) or less-affected hand (LAH), and pressing a button inside with the opposite hand. Temporal and spatial components of data were extracted and related to measures of hand function and level of impairment. Total task duration was correlated with the Jebsen–Taylor Test of Hand Function in both conditions (either hand leading with the lid-opening). Spatial accuracy of the LAH when the box was opened with their AH was correlated with outcomes on the Children’s Hand Use Experience Questionnaire. Additionally, we found a subgroup of children displaying non-symmetrical movement interference associated with greater movement overlap when their affected hand opened the box. This subgroup also demonstrated decreased use of the affected hand during bimanual tasks. Further investigation of bimanual interference, which goes beyond small scaled symmetrical mirrored movements, is needed to consider its impact on bimanual task performance following early unilateral brain injury.     

Hemispheric competition in left-handers on bimanual reaction time tasks

The authors examined possible differences in left- and right-handers on bimanual reaction times to centralized visual stimuli. Eighty participants (n = 40 in each group of left- and right-handers) were tested on unimanual and bimanual reaction time (RT) tasks. Consistently across the 2 groups, the dominant-hand RT was faster, on average, than the nondominant-hand RT, and unimanual RTs were faster than bimanual RTs. However, RT differences between hands revealed a higher percentage of dominant-hand-led trials in right-handers than in left-handers, despite similar absolute RT differences in the 2 groups. On the basis of those findings, the authors conclude that hand dominance does not generally determine which hand leads in a bimanual task and that left-handers have stronger between-hemisphere competition than right-handers do.