Event-related (de)synchronization and potential in whole vs. part sensorimotor learning.

Background: There are different ways to learn a sensorimotor task. This research focuses on whole versus part learning in a complex video game that involves sensorimotor adaptations and skill learning. The primary aim of this research is to compare the changes in (1) event-related potentials (ERP) and (2) Alpha and Beta event-related desynchronization/synchronization [ERD(S)] of EEG between whole and part practice protocols. Materials and methods: 18 Healthy young participants practiced for 5 days a video game with distorted kinematic (advancing skill) and dynamic features (shooting skill) to test the ability to combine sensorimotor skill components learned modularly (part learning, 9 participants) or combined (whole practice, 9 participants). We examined ERP and ERD(S) in EEG channels in the baseline test (day 1) and the retention test (day 5), dissociating epochs with advancing or shooting. We focus the analysis on the main activity of ERP or ERD(S) in different time windows. Results: In the advancing epochs (distorted kinematic), both groups showed a decrease in time for ERP and an increase in Beta ERD activity in central and posterior channels. In the shooting epochs (distorted dynamic), the Whole group showed a decrease in time for ERPs in anterior and central-posterior channels. Additionally, the shooting ERS in the Beta band decreases within sessions in central channels, particularly for the Part group. Conclusion: Neural correlates of kinematic and dynamic control [ERP and ERD(S)] were modulated by sensorimotor learning, which reflects the effect of the type of practice on the execution and the evaluation of the action. These results can be linked with our previous report, where the simultaneous practice of kinematic and dynamic distortions takes advantage of the motor performance on retention tests, indicating a more automatic control for the whole practice group.

Differentiation of the motor cost associated with cognitive tasks in Parkinson's disease: A dual-task study.

Parkinson's disease is a neurodegenerative condition associated with motor and cognitive impairments. While the execution of dual cognitive-motor tasks imposes a cost on gait velocity, it has been barely determined if the gait deterioration depends on the specific cognitive domain involved in the dual-task. Twenty-four subjects (12 patients with Parkinson's disease and 12 healthy subjects) carried out a single task (gait alone) and several dual tasks where the concurrent second task was the Trail Making Test (Part A) and the six tasks of the Frontal Assessment Battery. Gait variables were measured by accelerometry via smartphone. Data analysis included analysis of variance (ANOVA) and exploratory factorial analysis. Both groups showed a similar gait performance, except for velocity, where patients exhibited a bradykinetic profile. The dual-task during the Trail Making Test showed the highest motor cost. Frontal Assessment Battery's tasks as conceptualization, mental flexibility and motor programming showed a higher motor cost than the other tasks (sensibility to interference, inhibitory control and environmental autonomy). The factorial analysis applied to the motor costs confirmed two profiles, grouping those related to the dorsolateral prefrontal cortex (mental flexibility and motor programming tasks) in an independent factor. Among cognitive functions, attention is critical for gait control in Parkinson's disease and healthy elderly people. The interference posed by several executive operations suggests a specific competition in prefrontal regions that support dual tasks. Moreover, the higher cost for patients with Parkinson's disease patients emphasizes the cognitive decline and compensatory cognitive strategy for gait control related to attention and executive functions.

Oscillations in cortico-basal ganglia circuits: implications for Parkinson's disease and other neurologic and psychiatric conditions.

Cortico-basal ganglia circuits are thought to play a crucial role in the selection and control of motor behaviors and have also been implicated in the processing of motivational content and in higher cognitive functions. During the last two decades, electrophysiological recordings in basal ganglia circuits have shown that several disease conditions are associated with specific changes in the temporal patterns of neuronal activity. In particular, synchronized oscillations have been a frequent finding suggesting that excessive synchronization of neuronal activity may be a pathophysiological mechanism involved in a wide range of neurologic and psychiatric conditions. We here review the experimental support for this hypothesis primarily in relation to Parkinson's disease but also in relation to dystonia, essential tremor, epilepsy, and psychosis/schizophrenia.

Clinical improvement with intensive robot-assisted arm training in chronic stroke is unchanged by supplementary tDCS.

BACKGROUND: Intensive robot-assisted arm training in the chronic phase of stroke recovery can lead to clinical improvement. Combinatorial therapeutic approaches are sought to further optimize stroke recovery. Transcranial direct current stimulation (tDCS) is one candidate to combine with robotic training, as transient increases in excitability and improvements in motor behavior have separately been reported. OBJECTIVE: To determine whether tDCS, delivered prior to robotic training, could augment clinical improvement. METHODS: We conducted a dual-site, randomized controlled trial in 82 chronic ischemic stroke patients (inclusion > 6 m post-injury, dominant hemisphere, first stroke; residual hemiparesis) who were split into two groups to receive tDCS (M1-SO montage, anode ipsilesional, 5×7 cm electrodes, 2 mA, 20 mins) or sham tDCS, prior to robotic upper-limb training (12 weeks; 36 sessions; shoulder-elbow robot or wrist robot on alternating sessions). The primary end-point was taken after 12 weeks of training, and assessed with the Upper Extremity Fugl-Meyer impairment scale (FM). Corticomotor conduction was assessed with transcranial magnetic stimulation (TMS). RESULTS: For the combined group (n = 82; post-training) robotic training increased the FM by 7.36 points compared to baseline (p < 0.0001). There was no difference in the FM increase between the tDCS and sham groups (6.97 and 7.73 respectively, p = 0.46). In both groups, clinically meaningful improvement (≥5 points) from baseline was evident in the majority of patients (56/77), was sustained six months later (54/72), and could be attained in severe, moderate and mild baseline hemiparesis. Clinical improvement was associated with increased excitability in the affected hemisphere as assessed by resting motor threshold (pre-post p = 0.029; pre-post 6 months p = 0.029), but not with threshold-adjusted assessment of MEP amplitude (pre-post p = 0.09; pre-post 6 months p = 0.15). Participants with motor evoked potentials were more likely to improve clinically than those without (17/18, 94%, versus 39/59, 66%, p = 0.018). CONCLUSIONS: Our study confirms the benefit of intensive robot-assisted training in stroke recovery, and indicates that conventional tDCS does not confer further advantage to robotic training. We also showed that corticospinal integrity, as assessed by TMS, is a predictor of clinically meaningful response to intensive arm therapy in chronic stroke.

Parallel learning processes of a visuomotor adaptation task in a changing environment.

During the control of reaching movements, a key contribution of the visual system is the localization of relevant environmental targets. In motor adaptation processes, the visual evaluation of effector motor behavior enables learning from errors, which demands continuous visual attentional focus. However, most current adaptation paradigms include static targets; therefore, when a learning situation develops in a highly variable environment and there is a double demand for visual resources (environment and motor performance), the evolution of learning processes is unknown. In order to understand how learning processes evolve in a variable environment, a video game task was designed in which subjects were asked to manage a 60° counterclockwise-rotated cursor to capture descending targets with initially unpredictable trajectories. During the task, the cursor and eye movements were recorded to dissect visuomotor coordination. We observed that the pursuit of the targets conditioned a predominant and continuous visual inspection of the environment instead of the rotated cursor. As learning progressed, subjects exhibited a linear reduction in directional error and selected a motor strategy based on the degree of reward, which improved the performance. These results suggest that when the environment demands high visual attention, error-based and reinforced motor learning processes are implemented simultaneously, thus enabling efficient predictive behavior.

Visuomotor coordination and cortical connectivity of modular motor learning.

The ability to transfer sensorimotor skill components to new actions and the capacity to use skill components from whole actions are characteristic of the adaptability of the human sensorimotor system. However, behavioral evidence suggests complex limitations for transfer after combined or modular learning of motor adaptations. Also, to date, only behavioral analysis of the consequences of the modular learning has been reported, with little understanding of the sensorimotor mechanisms of control and the interaction between cortical areas. We programmed a video game with distorted kinematic and dynamic features to test the ability to combine sensorimotor skill components learned modularly (composition) and the capacity to use separate sensorimotor skill components learned in combination (decomposition). We examined motor performance, eye-hand coordination, and EEG connectivity. When tested for integrated learning, we found that combined practice initially performed better than separated practice, but differences disappeared after integrated practice. Separate learning promotes fewer anticipatory control mechanisms (depending more on feedback control), evidenced in a lower gaze leading behavior and in higher connectivity between visual and premotor domains, in comparison with the combined practice. The sensorimotor system can acquire motor modules in a separated or integrated manner. However, the system appears to require integrated practice to coordinate the adaptations with the skill learning and the networks involved in the integrated behavior. This integration seems to be related to the acquisition of anticipatory mechanism of control and with the decrement of feedback control.