Interactions between new and pre-existing dynamics in bimanual movement control

Direct evidence of EEG coherence in alleviating phantom limb pain by virtual referred sensation: Case report

Virtual reality (VR) systems have been integrated into rehabilitation techniques for phantom limb pain (PLP). In this case report, we used electroencephalography (EEG) to analyze corticocortical coherence between the bilateral sensorimotor cortices during vibrotactile stimulation in conjunction with VR rehabilitation in two PLP patients. As a result, we observed PLP alleviation and increased alpha wave coherence during VR rehabilitation when stimulation was delivered to the cheek and shoulder (referred sensation areas) of the affected side. Vibrotactile stimulation with VR rehabilitation may enhance the awareness and movement of the phantom hand.

Post-task Effects on EEG Brain Activity Differ for Various Differential Learning and Contextual Interference Protocols

A large body of research has shown superior learning rates in variable practice compared to repetitive practice. More specifically, this has been demonstrated in the contextual interference (CI) and in the differential learning (DL) approach that are both representatives of variable practice. Behavioral studies have indicate different learning processes in CI and DL. Aim of the present study was to examine immediate post-task effects on electroencephalographic (EEG) brain activation patterns after CI and DL protocols that reveal underlying neural processes at the early stage of motor consolidation. Additionally, we tested two DL protocols (gradual DL, chaotic DL) to examine the effect of different degrees of stochastic fluctuations within the DL approach with a low degree of fluctuations in gradual DL and a high degree of fluctuations in chaotic DL. Twenty-two subjects performed badminton serves according to three variable practice protocols (CI, gradual DL, chaotic DL), and a repetitive learning protocol in a within-subjects design. Spontaneous EEG activity was measured before, and immediately after each 20-min practice session from 19 electrodes. Results showed distinguishable neural processes after CI, DL, and repetitive learning. Increases in EEG theta and alpha power were obtained in somatosensory regions (electrodes P3, P7, Pz, P4, P8) in both DL conditions compared to CI, and repetitive learning. Increases in theta and alpha activity in motor areas (electrodes C3, Cz, C4) were found after chaotic DL compared to gradual DL, and CI. Anterior areas (electrodes F3, F7, Fz, F4, F8) showed increased activity in the beta and gamma bands after CI. Alpha activity was increased in occipital areas (electrodes O1, O2) after repetitive learning. Post-task EEG brain activation patterns suggest that DL stimulates the somatosensory and motor system, and engages more regions of the cortex than repetitive learning due to a tighter stimulation of the motor and somatosensory system during DL practice. CI seems to activate specifically executively controlled processing in anterior brain areas. We discuss the obtained patterns of post-training EEG traces as evidence for different underlying neural processes in CI, DL, and repetitive learning at the early stage of motor learning.

Differential Training Facilitates Early Consolidation in Motor Learning

Current research demonstrates increased learning rates in differential learning (DL) compared to repetitive training. To date, little is known on the underlying neurophysiological processes in DL that contribute to superior performance over repetitive practice. In the present study, we measured electroencephalographic (EEG) brain activation patterns after DL and repetitive badminton serve training. Twenty-four semi-professional badminton players performed badminton serves in a DL and repetitive training schedule in a within-subjects design. EEG activity was recorded from 19 electrodes according to the 10–20 system before and immediately after each 20-min exercise. Increased theta activity was obtained in contralateral parieto-occipital regions after DL. Further, increased posterior alpha activity was obtained in DL compared to repetitive training. Results indicate different underlying neuronal processes in DL and repetitive training with a higher involvement of parieto-occipital areas in DL. We argue that DL facilitates early consolidation in motor learning indicated by post-training increases in theta and alpha activity. Further, brain activation patterns indicate somatosensory working memory processes where attentional resources are allocated in processing of somatosensory information in DL. Reinforcing a somatosensory memory trace might explain increased motor learning rates in DL. Finally, this memory trace is more stable against interference from internal and external disturbances that afford executively controlled processing such as attentional processes.

Bimanual force control: cooperation and interference?

Three experiments were designed to determine the level of cooperation or interference observed from the forces generated in one limb on the forces exhibited by the contralateral limb when one or both limbs were producing a constant force (Experiment 1), one limb was producing a dynamic force while the other limb was producing a constant force (Experiment 2), and both limbs were producing dynamic force patterns (Experiment 3). The results for both Experiments 1 and 2 showed relatively strong positive time series cross correlations between the left and right limb forces indicating increases or decreases in the forces generated by one limb resulted in corresponding changes in the forces produced by the homologous muscles of the contralateral limb. Experiment 3 required participants to coordinate 1:1 and 1:2 rhythmical bimanual force production tasks when provided Lissajous feedback. The results indicated very effective performance of both bimanual coordination patterns. However, identifiable influences of right limb forces on the left limb force time series were observed in the 1:2 coordination pattern but not in the 1:1 pattern. The results of all three experiments support the notion that neural crosstalk is partially responsible for the stabilities and instabilities associated with bimanual coordination.

An evaluation of the effectiveness of PROMPT therapy in improving speech production accuracy in six children with cerebral palsy

This study evaluates perceptual changes in speech production accuracy in six children (3-11 years) with moderate-to-severe speech impairment associated with cerebral palsy before, during, and after participation in a motor-speech intervention program (Prompts for Restructuring Oral Muscular Phonetic Targets). An A1BCA2 single subject research design was implemented. Subsequent to the baseline phase (phase A1), phase B targeted each participant's first intervention priority on the PROMPT motor-speech hierarchy. Phase C then targeted one level higher. Weekly speech probes were administered, containing trained and untrained words at the two levels of intervention, plus an additional level that served as a control goal. The speech probes were analysed for motor-speech-movement-parameters and perceptual accuracy. Analysis of the speech probe data showed all participants recorded a statistically significant change. Between phases A1-B and B-C 6/6 and 4/6 participants, respectively, recorded a statistically significant increase in performance level on the motor speech movement patterns targeted during the training of that intervention. The preliminary data presented in this study make a contribution to providing evidence that supports the use of a treatment approach aligned with dynamic systems theory to improve the motor-speech movement patterns and speech production accuracy in children with cerebral palsy.

Aging effects on the resting state motor network and interlimb coordination

Both increases and decreases in resting state functional connectivity have been previously observed within the motor network during aging. Moreover, the relationship between altered functional connectivity and age-related declines in bimanual coordination remains unclear. Here, we explored the developmental dynamics of the resting brain within a task-specific motor network in a sample of 128 healthy participants, aged 18-80 years. We found that age-related increases in functional connectivity between interhemispheric dorsal and ventral premotor areas were associated with poorer performance on a novel bimanual visuomotor task. Additionally, a control analysis performed on the default mode network confirmed that our age-related increases in functional connectivity were specific to the motor system. Our findings suggest that increases in functional connectivity within the resting state motor network with aging reflect a loss of functional specialization that may not only occur in the active brain but also in the resting brain.

The effects of task demands on bimanual skill acquisition

Bimanual coordination is essential for everyday activities. It is thought that different degrees of demands may affect learning of new bimanual patterns. One demand is at the level of performance and involves breaking the tendency to produce mirror-symmetric movements. A second is at a perceptual level and involves controlling each hand to separate (i.e., split) goals. A third demand involves switching between different task contexts (e.g., a different uni- or bimanual task), instead of continuously practicing one task repeatedly. Here, we studied the effect of these task demands on motor planning (reaction time) and execution (error) while subjects learned a novel bimanual isometric pinch force task. In Experiment 1, subjects continuously practiced in one of the two extremes of the following bimanual conditions: (1) symmetric force demands and a perceptually unified target for each hand or (2) asymmetric force demands and perceptually split targets. Subjects performing in the asymmetric condition showed some interference between hands, but all subjects, regardless of group, could learn the isometric pinch force task similarly. In Experiment 2, subjects practiced these and two other conditions, but in a paradigm where practice was briefly interrupted by the performance of either a unimanual or a different bimanual condition. Reaction times were longer and errors were larger well after the interruption when the main movement to be learned required asymmetric forces. There was no effect when the main movement required symmetric forces. These findings demonstrate two main points. First, people can learn bimanual tasks with very different demands on the same timescale if they are not interrupted. Second, interruption during learning can negatively impact both planning and execution and this depends on the demands of the bimanual task to be learned. This information will be important for training patient populations, who may be more susceptible to increased task demands.

Motor coordination dynamics underlying graphic motion in 7- to 11-year-old children

Using concepts and tools of a dynamical system approach in order to understand motor coordination underlying graphomotor skills, the aim of the current study was to establish whether the basic coordination dynamics found in adults is already established in children at elementary school, when handwriting is trained and eventually acquired. In the study, 45 children and 9 adults volunteered to copy two series of 13 ellipsoid shapes. These shapes were generated by manipulating the relative phase between 0° and 180° of two orthogonal oscillators in two orientations. Findings showed that although children from an early age onward and adults reproduced straight lines precisely (i.e., 0° and 180°), the former drew ellipsoid shapes in a less eccentric fashion than the latter (i.e., ∼90° in all children rather than ∼60° and 120° in adults). This tendency to write in a rounder fashion persists until 11 years of age, suggesting that the coordination dynamics underlying graphomotor skills and tentatively shaping the coordinated activity involved in adult handwriting appears only later, probably due to increasing constraints on speed.

Testing multiple coordination constraints with a novel bimanual visuomotor task

The acquisition of a new bimanual skill depends on several motor coordination constraints. To date, coordination constraints have often been tested relatively independently of one another, particularly with respect to isofrequency and multifrequency rhythms. Here, we used a new paradigm to test the interaction of multiple coordination constraints. Coordination constraints that were tested included temporal complexity, directionality, muscle grouping, and hand dominance. Twenty-two healthy young adults performed a bimanual dial rotation task that required left and right hand coordination to track a moving target on a computer monitor. Two groups were compared, either with or without four days of practice with augmented visual feedback. Four directional patterns were tested such that both hands moved either rightward (clockwise), leftward (counterclockwise), inward or outward relative to each other. Seven frequency ratios (3∶1, 2∶1, 3∶2, 1∶1, 2∶3. 1∶2, 1∶3) between the left and right hand were introduced. As expected, isofrequency patterns (1∶1) were performed more successfully than multifrequency patterns (non 1∶1). In addition, performance was more accurate when participants were required to move faster with the dominant right hand (1∶3, 1∶2 and 2∶3) than with the non-dominant left hand (3∶1, 2∶1, 3∶2). Interestingly, performance deteriorated as the relative angular velocity between the two hands increased, regardless of whether the required frequency ratio was an integer or non-integer. This contrasted with previous finger tapping research where the integer ratios generally led to less error than the non-integer ratios. We suggest that this is due to the different movement topologies that are required of each paradigm. Overall, we found that this visuomotor task was useful for testing the interaction of multiple coordination constraints as well as the release from these constraints with practice in the presence of augmented visual feedback.

Coordination dynamics of elliptic shape drawing: effects of orientation and eccentricity

The aim of the present study was to show the effect of orientation on producing ellipses of various eccentricities. Ten right-handed adults were required to reproduce eight series of 84 ellipses on a graphic tablet at spontaneous speed. The ellipses displayed seven eccentricities, corresponding to the Lissajous plot produced by two orthogonal harmonic oscillators whose relative phase (RP) varied from 0° (a line) to 90° (a circle), and twelve orientations, the long axis of the ellipses aligned in a direction ranging from three to nine o'clock with respect to the body transverse plane. Results confirmed the participant's preference for two eccentricities, 0° and 45°, that is, a line and an ellipse of intermediate eccentricity, respectively. Except for the circle, insensitive to orientation by definition, orientation became a cogent constraint: In the 10:30 o'clock direction, line drawing (0° RP) increased in variability and the intermediate ellipse (45° RP) was attracted towards a circle (90° RP). These findings suggest an interaction between orientation effects, putatively due to differences in the motion of the wrist and fingers, and eccentricity effects, which may pertain to preferences arising from the non-linear coupling between the effectors.