Bimanual movement training (BMT) of the upper extremity has been found to improve sensorimotor function of the stroke affected limb for some patients; however, the neurophysiological mechanism underlying behavioural enhancement remains unclear. Determining a measurement tool to gauge within-session cortical excitability modulations in response to training would be advantageous for stroke rehabilitation practitioners not only to understand the mechanism underlying behavioural enhancement, but it would also assess the usefulness of training interventions from an individualistic perspective. The purposes of the current thesis were four fold: 1) to gain a better understanding of the neurophysiological effects of short-term visually cued BMT, of varying types, upon the trained bimanual task and those that generalize to a unimanual task by way of the cue-related movement-related potential (MRP). 2) To determine the generators of the cue-related MRP, an event-related potential (ERP) associated with the preparation and execution of a cued movement versus the Bereitschaftspotential (BP), a similar ERP associated with self-paced movement, 3) to investigate kinematic parameters that may influence the cue-related MRP and 4) to investigate the usefulness of the MRP as a future measurement tool to assess within-session changes of cortical excitability associated with training interventions in the stroke patient population. For the purposes of establishing control data for future stroke related studies, the current thesis was devised to investigate the healthy population. We hypothesized that inphase (homologous motor movement) BMT more so than antiphase (antagonistic motor movement) BMT would induce cortical excitability modulations within preparatory and executory cortical regions for the trained bimanual task and a similar unimanual task. Two experiments using EEG and subsequent cue-related MRP revealed that inphase BMT more so than antiphase BMT enhanced the amplitude of the early MRP component denoting preparatory excitability, but not the late MRP component representing executory excitability, and this modulation would also occur despite a simulated flexion contracture. The localization of the cue-related early MRP was found to be predominantly over the lateral premotor cortex, differing from the self-paced early BP determined to predominantly represent SMA excitability. Further confirmation of the localization of the cue-related early MRP versus the self-paced early BP was obtained in another experiment where it was revealed that cued inphase BMT did not affect the amplitude of the early BP (SMA excitability) of a self-paced movement; therefore, cued inphase BMT did not modulate SMA excitability. In a fourth experiment, kinematic parameters such as movement rate, range of motion (ROM) and force production at movement onset or as an inertial load were assessed in relation to modulations of the three cue-related MRP components. The results indicated that the various kinematic parameters had differential modulatory effects upon the cue-related MRP. As a whole, the results of the thesis indicated that 1) the cue-related MRP can be used to assess within-session training-related cortical adaptations in response to inphase BMT. 2) MRP modulations in response to cued inphase BMT remain evident despite a restriction of range of motion and imposed tonic load, indicating the potential to use the MRP in the stroke patient population in future research. 3) The localization of the early MRP component of a cue-related movement originates from the lateral premotor cortex versus the SMA responsible for the early BP component of a self-paced movement, and 4) in order to use the MRP as a measure of cortical excitability, kinematic parameters such as a load placed upon the musculature must be controlled in an experimental design. The results of the experiments provide insight into the use of the cue-related MRP as a measure of cortical excitability modulation in response to cued inphase BMT, and will inform future training-related studies using the cued MRP as a measure of learning related adaptation in the healthy and stroke patient populations.

Bimanual movement training (BMT) of the upper extremity has been found to improve sensorimotor function of the stroke affected limb for some patients; however, the neurophysiological mechanism underlying behavioural enhancement remains unclear. Determining a measurement tool to gauge within-session cortical excitability modulations in response to training would be advantageous for stroke rehabilitation practitioners not only to understand the mechanism underlying behavioural enhancement, but it would also assess the usefulness of training interventions from an individualistic perspective. The purposes of the current thesis were four fold: 1) to gain a better understanding of the neurophysiological effects of short-term visually cued BMT, of varying types, upon the trained bimanual task and those that generalize to a unimanual task by way of the cue-related movement-related potential (MRP). 2) To determine the generators of the cue-related MRP, an event-related potential (ERP) associated with the preparation and execution of a cued movement versus the Bereitschaftspotential (BP), a similar ERP associated with self-paced movement, 3) to investigate kinematic parameters that may influence the cue-related MRP and 4) to investigate the usefulness of the MRP as a future measurement tool to assess within-session changes of cortical excitability associated with training interventions in the stroke patient population. For the purposes of establishing control data for future stroke related studies, the current thesis was devised to investigate the healthy population. We hypothesized that inphase (homologous motor movement) BMT more so than antiphase (antagonistic motor movement) BMT would induce cortical excitability modulations within preparatory and executory cortical regions for the trained bimanual task and a similar unimanual task. Two experiments using EEG and subsequent cue-related MRP revealed that inphase BMT more so than antiphase BMT enhanced the amplitude of the early MRP component denoting preparatory excitability, but not the late MRP component representing executory excitability, and this modulation would also occur despite a simulated flexion contracture. The localization of the cue-related early MRP was found to be predominantly over the lateral premotor cortex, differing from the self-paced early BP determined to predominantly represent SMA excitability. Further confirmation of the localization of the cue-related early MRP versus the self-paced early BP was obtained in another experiment where it was revealed that cued inphase BMT did not affect the amplitude of the early BP (SMA excitability) of a self-paced movement; therefore, cued inphase BMT did not modulate SMA excitability. In a fourth experiment, kinematic parameters such as movement rate, range of motion (ROM) and force production at movement onset or as an inertial load were assessed in relation to modulations of the three cue-related MRP components. The results indicated that the various kinematic parameters had differential modulatory effects upon the cue-related MRP. As a whole, the results of the thesis indicated that 1) the cue-related MRP can be used to assess within-session training-related cortical adaptations in response to inphase BMT. 2) MRP modulations in response to cued inphase BMT remain evident despite a restriction of range of motion and imposed tonic load, indicating the potential to use the MRP in the stroke patient population in future research. 3) The localization of the early MRP component of a cue-related movement originates from the lateral premotor cortex versus the SMA responsible for the early BP component of a self-paced movement, and 4) in order to use the MRP as a measure of cortical excitability, kinematic parameters such as a load placed upon the musculature must be controlled in an experimental design. The results of the experiments provide insight into the use of the cue-related MRP as a measure of cortical excitability modulation in response to cued inphase BMT, and will inform future training-related studies using the cued MRP as a measure of learning related adaptation in the healthy and stroke patient populations.

The primary purpose of this study was to examine if the coupling effect could be overcome in a bimanual isometric tracking task, using methods similar to those of the Kovacs et al. team in previous bimanual kinematic research. Thirty right-handed participants, with a mean age 22.5 (SD 3.5) years, free from any neurological disorder or physical ailment, were randomly assigned to one of three groups that differed in percent of feedback provided during the practice trials (100%, 50% or 0%). The participants then performed a bimanual isometric manipulation tracking task that was a 2:1 rhythm (backwards C shape) scaled to 30% maximum voluntary contraction (MVC). Participants performed five blocks of five trials with the feedback schedule assigned to their group, rested for 30 minutes, then performed a retention task. Significant differences (p<.05) in Root Mean Square Error (RMSE) occurred between the 100% group and both the 50% and 0% groups during the practice blocks. Significant differences (p<.05) also occurred between the 50% group and the 100% and 0% group for the first four practice blocks. Though differences occurred between the groups during the practice trials, no differences occurred between the groups during the retention block. These findings support the position that the coupling effect in bimanual isometric manipulation tasks is very strong and cannot be as easily overcome as it is in kinematic bimanual task. This may be due to the feedback systems used in isometric conditions versus kinematic tasks (i.e. force and pressure sensation vs. position and motion proprioception). / text

Popular theories of motor learning (e.g., Adams, 1971; Schmidt, 1975) rely heavily on formation of new skills through refinements of pre-existing ones. Dynamic Pattern Theory has the advantage of being able to assess initial individual differences on the required task so that the subject becomes the important unit of measure. The general purpose was to identify the reciprocal influence of intrinsic patterns and learning a new pattern. In two experiments subjects were required to practice a rhythmic bimanual coordination task of the forearms using linear sliding devices. In the first experiment, 7 subjects practiced a 90° relative phase pattern for 45, 15 s trials on each of 6 practice days. In-phase and anti-phase trials were performed pre-and post-practice. Subjects were provided terminal feedback with a Lissajou figure after each practice trial and augmented feedback was provided after every 5th practice trial. Mean constant error (CE) for individual subject data and absolute CE (|CE|) for group data were used as measures of accuracy. Standard deviation of relative phase was used as a measure of stability (VE). Subjects were able to learn the 90° pattern and performance plateaued by the fourth practice day. Neither intrinsic pattern showed any destabilization, although a temporary decrease in accuracy (CE) within days was found. The four week retention test revealed no change for any pattern. Experiment 2 compared two groups practicing either 45° or 135° relative phase. It was predicted that the 135° relative phase pattern would be easier to learn because of the reduced competition from the less stable 180° intrinsic pattern. The procedure was similar to Experiment 1 except that subjects practiced for only four days. Performance of the practiced patterns was never as accurate as 0° and 180° but variability of performance was not different for both practiced and intrinsic patterns by Day 4. There was no difference in either accuracy or stability between the two groups on the practiced patterns. As in Experiment 1, there was no change from the last day of practice to the four week retention test. Individual subject data revealed numerous different paths to learning the required pattern. Constant error and VE values for intrinsic patterns were not particularly good predictors of ability to learn the practiced pattern. Additionally, a low VE was not indicative of a low CE or vice-versa when practicing the required pattern. The results from both experiments show that early in learning, competition biases performance away from the intrinsic attractors. Later in practice, subjects stabilize their performance of the new pattern and the intrinsic patterns do not destabilize. Differences in performance of the required pattern may have depended, not only on dynamic principles, but also on motivation, handedness, and conceptualization of the task. / Thesis / Master of Science (MSc)

Grasping is fundamentally important for our successful interaction with the environment. Grasping with both hands is phylogenetically older than the hand yet its underlying mechanisms are poorly understood. The objective of this research is to examine bimanual grasping and its underlying mechanisms. Two experiments were conducted to examine whether bimanual grasping involves both hemispheres equally or only one dominant hemisphere, and to examine whether information crosses at an early visual level and/or at later sensorimotor/motor levels. The first experiment examined participants’ grasping and reaching movements while they fixated either to the left or right of the object. For the second experiment, EEG data was recorded while participants performed a similar task. The results from both experiments suggested that when we grasp an object with both hands, the left and right hemispheres control the action equally, and visual information is shared before it reaches areas that are involved in motor control.

Grasping is fundamentally important for our successful interaction with the environment. Grasping with both hands is phylogenetically older than the hand yet its underlying mechanisms are poorly understood. The objective of this research is to examine bimanual grasping and its underlying mechanisms. Two experiments were conducted to examine whether bimanual grasping involves both hemispheres equally or only one dominant hemisphere, and to examine whether information crosses at an early visual level and/or at later sensorimotor/motor levels. The first experiment examined participants’ grasping and reaching movements while they fixated either to the left or right of the object. For the second experiment, EEG data was recorded while participants performed a similar task. The results from both experiments suggested that when we grasp an object with both hands, the left and right hemispheres control the action equally, and visual information is shared before it reaches areas that are involved in motor control.

A number of movements produced in everyday life require not only coordination of joints within a limb, but also coordination between one or more limbs. The aim of this dissertation was to examine the influence of biomechanical constraints on intralimb coordination, interlimb coordination, and learning. Experiment 1 sought to determine if principles of the Leading Joint Hypothesis, when applied to a multijoint bimanual coordination task, could provide insight into the contribution of intralimb dynamics to interlimb coordination. Participants repetitively traced ellipse templates in an asymmetrical coordination pattern (i.e. both limbs moving counter-clockwise). Kinematic data of the upper limbs were recorded with a VICON camera system. Ellipse templates were oriented either tilted right or tilted left; yielding a total of four left arm-right arm leading joint combinations. The findings indicated that stability of interlimb coordination patterns were found to be influenced by whether arm movements were produced with similar or different leading joints. Bimanual asymmetric ellipse-tracing produced with similar leading joints were more stable than patterns produced with different leading joints. For example, asymmetric coordination patterns produced with similar leading joints exhibited less transient behavior than coordination patterns produced with different leading joints (p < .01). Experiment 2 expanded on these findings by employing a similar task and incorporating a learning component to assess how intralimb dynamics are tuned with practice of a novel coordination pattern. Participants were randomly assigned to one of three groups. One group practiced tracing a pair of ellipse templates that were oriented in such a way that required similar leading joints while the other two groups practiced tracing ellipse templates that required different leading joints. Early in practice, the group learning the coordination pattern with similar leading joints exhibited greater interlimb stability than the two groups learning with different leading joints. However, following two days of practice, performance of the groups learning with different leading joints improved to match that of the group learning with similar leading joints. The findings suggest that initial biomechanical constraints can be overcome with practice, resulting in similar performance regardless of whether being produced with similar or different leading joints.

A number of movements produced in everyday life require not only coordination of joints within a limb, but also coordination between one or more limbs. The aim of this dissertation was to examine the influence of biomechanical constraints on intralimb coordination, interlimb coordination, and learning. Experiment 1 sought to determine if principles of the Leading Joint Hypothesis, when applied to a multijoint bimanual coordination task, could provide insight into the contribution of intralimb dynamics to interlimb coordination. Participants repetitively traced ellipse templates in an asymmetrical coordination pattern (i.e. both limbs moving counter-clockwise). Kinematic data of the upper limbs were recorded with a VICON camera system. Ellipse templates were oriented either tilted right or tilted left; yielding a total of four left arm-right arm leading joint combinations. The findings indicated that stability of interlimb coordination patterns were found to be influenced by whether arm movements were produced with similar or different leading joints. Bimanual asymmetric ellipse-tracing produced with similar leading joints were more stable than patterns produced with different leading joints. For example, asymmetric coordination patterns produced with similar leading joints exhibited less transient behavior than coordination patterns produced with different leading joints (p < .01). Experiment 2 expanded on these findings by employing a similar task and incorporating a learning component to assess how intralimb dynamics are tuned with practice of a novel coordination pattern. Participants were randomly assigned to one of three groups. One group practiced tracing a pair of ellipse templates that were oriented in such a way that required similar leading joints while the other two groups practiced tracing ellipse templates that required different leading joints. Early in practice, the group learning the coordination pattern with similar leading joints exhibited greater interlimb stability than the two groups learning with different leading joints. However, following two days of practice, performance of the groups learning with different leading joints improved to match that of the group learning with similar leading joints. The findings suggest that initial biomechanical constraints can be overcome with practice, resulting in similar performance regardless of whether being produced with similar or different leading joints.

The present study was conducted to examine the process of consolidation when learning a difficult bimanual coordination pattern. There are two phenomena associated with the process of consolidation, an enhancement in performance without additional practice and the stabilization observed as resistance to interference from a similar task after acquisition of a novel skill. Both phenomena have been widely examined in sequence skill learning studies. However, few studies have examined the consolidation effect after training of a continuous and rhythmic bimanual coordination pattern. The first goal of this study was to determine if sleep enhances the performance of a minimally trained 1:2 pattern of bimanual coordination in a manner that has been observed with sequencing skills, that is, performance significantly improves after an overnight sleep. A recent study by Buchanan & Wang (in-press) showed that by manipulating the position of a visual-augmented-feedback cursor, either behind or to-the-side of a 1:2 bimanual coordination template, an advantage of the side cursor position was found in the no-feedback retention test after a fifteen-minute break. The second goal was to test whether an overnight sleep may reduce the guidance effect associated with the behind cursor position as reported in Buchanan & Wang (in-press). In the present experiment, the effect of an overnight sleep on learning a 1:2 pattern of bimanual coordination was accessed with six test trials presented immediately (IMM group) or 24 hours (SLEEP group) after 5 minutes of practice. The test trials included three trials with feedback and three trials with feedback removed. For either the IMM or SLEEP group, half of the participants practiced with the behind cursor position and the other half practiced with the side cursor position. The results indicated that the SLEEP group showed an improvement in performance from the acquisition trials to the feedback test trials whereas the IMM group did not. The advantage of the side cursor position at the no-feedback retention test was not evident in the current study. These results are consistent with our two predictions and provide evidence of enhancement in learning a 1:2 pattern bimanual coordination skill.

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