Premotor function in interpersonal bimanual coordination: Neural responses to varying frequencies and spatio-temporal relationships.

BACKGROUND: Interpersonal movement coordination is an important aspect of daily life. Behavioral studies have found that rhythmic bimanual coordination of movement is mainly influenced by two factors, spatio-temporal relationship and frequency of movements. How these factors affect action coordination at the neural level needs further exploration. The current study used a factor design to investigate the brain basis of movement coordination under various spatiotemporal relationships and frequencies, as well as their intricate interaction. METHODS: Participants were asked to perform symmetric or alternating hand movements under conditions of different spatio-temporal relationships (symmetric, alternating) and frequencies. A multi-channel, continuous wave, functional near-infrared spectral (fNIRS) imaging instrument was used to monitor hemodynamic activity while 16 pairs of volunteers performed the task. RESULTS: Behaviorally, as indexed by phase locking value, movements were more stable in symmetric mode than in alternate mode. With increasing frequency, symmetric mode became more unstable; in contrast, alternating mode became more stable at higher frequencies, suggesting phase transition. Activation in brain regions of interest was much stronger in symmetric mode as compared with alternate mode. In alternate mode, but not symmetric mode, [HbO] varied with frequency. CONCLUSION: Interpersonal bimanual coordination involves activity in premotor areas (premotor cortex, supplementary motor area, and frontal eye fields). More oxygen is consumed in these regions in alternating mode than in symmetric mode.

Use of fNIRS to Characterize the Neural Mechanism of Inter-Individual Rhythmic Movement Coordination.

Background: Inter-individual rhythmic movement coordination plays an important role in daily life, particularly in competitive sports. Behaviorally, it is more challenging to coordinate alternating movements than symmetrical movements. The neural activity underlying these different movement coordination modes remains to be clarified, particularly considering complex inter-individual coordination differences. Methods: To further test the neural basis of inter-individual rhythmic movement coordination, a revised experimental paradigm of inter-individual coordination was adopted. Participants were asked to perform symmetric, alternate, or single movements (swinging the lower part of the leg) in the same rhythm. A multi-channel, continuous wave, functional near-infrared spectral (fNIRS) imaging instrument was used to monitor hemodynamic activity while 40 volunteers (9 male pairs and 11 female pairs) performed the task. Multivariate analyses of variance were conducted to compare mean oxy-hemoglobin concentration ([HbO]) across experimental conditions. Results: A significant three-way interaction (leg-swing condition × ROI × laterality) on mean [HbO] was observed. Post hoc analysis revealed a significant main effect of leg-swing condition only in brain regions of interest [right inferior parietal lobule (IPL)] contralateral to movement execution. Activation in brain regions of interest [right inferior parietal lobule (IPL)] was much stronger in alternate mode compared with symmetric or single modes, and the differences between symmetric and single mode were not statistically significant. This result suggests that the alternate mode of movement coordination was more likely to be supported by the IPL region than the other modes. Conclusion: The present findings provide neural evidence relevant to the theory of self-organization of movement coordination, in which an alternating movement mode appeared to be a more demanding condition than symmetrical movement.

The Relationship between Biological Motion-Based Visual Consciousness and Attention: An Electroencephalograph Study.

Understanding and predicting the intentions of others through limb movements are vital to social interaction. The processing of biological motion is unique from the processing of motion of inanimate objects. Presently, there is controversy over whether visual consciousness of biological motion is regulated by visual attention. In addition, the neural mechanisms involved in biological motion-related visual awareness are not known. In the current study, the relationship between visual awareness (aware vs unaware), represented by a point-light walker and biological-motion-based attention, manipulated by a difference in congruence (congruent, incongruent) between the direction of a pre-cue and that of biological motion was explored. The neural mechanisms involved in processing the stimuli were explored through electroencephalography. Both early (50-150 ms, 100-200 ms, and 174-226 ms after target presentation) and late (350-550 ms after target presentation) awareness-related neural processings were observed during a biological motion-based congruency task. Early processing was localized to occipital-parietal regions, such as the left postcentral gyrus, the left middle occipital gyrus, and the right precentral gyrus. In the 174-226-ms window, the activity in the occipital region was gradually replaced by activity in the parietal and frontal regions. Late processing was localized to frontal-parietal regions, such as the right dorsal superior frontal gyrus, the left medial superior frontal gyrus, and the occipito-temporal regions. Congruency-related processing occurred in the 246-260-ms window and was localized to the right superior occipital gyrus. In summary, due to its complexity, biological motion awareness has a unique neural basis.

Selective Effects of Postural Control on Spatial vs. Nonspatial Working Memory: A Functional Near-Infrared Spectral Imaging Study.

Background: Previous evidence suggests that postural control processing may be more related to spatial working memory (SWM) than to nonspatial working memory (NWM). Methodological discrepancies between spatial and nonspatial cognitive tasks have made direct comparisons between the two systems difficult. Methods: To explore the neural mechanisms of SWM and NWM relative to that of postural control, participants were subjected a cognitive-posture dual-task paradigm, consisting of a 3-back letter working memory (WM) task, using physically identical stimuli with spatial and nonspatial components memorized in different sessions, and a standing balance task with a tandem stance. Additionally, there were two control sessions: a single-postural control session wherein participants pressed mouse buttons at random while standing; and a single-cognitive task control session wherein subjects completed a WM task while seated. The subjects underwent functional near-infrared spectral imaging (fNIRS) during task performance, wherein oxygenated hemoglobin concentration ([HbO]) was measured in frontal and parietal regions. Results: Postural control reduced discernment in the SWM task significantly, but did not affect NWM task performance. fNIRS showed that postural control had a significant tendency to decrease the [HbO] in the frontal-parietal network of the left hemisphere when participants completed the SWM task. No posture-associated differences in [HbO] were observed in NWM-related areas during NWM task performance. Behavioral and fNIRS data demonstrated that postural control had a selective interaction with SWM. Specifically, postural control reduced SWM discrimination and SWM-related brain activity (frontal-parietal network), but not NWM discrimination or NWM-related brain activity. Furthermore, the multiple linear regression analysis showed that SWM, but not NWM, was an important predictor of postural control. These results suggest that postural control may share more cognitive resources with SWM than with NWM.