This title appears in the Scientific Report :
2016
Motor system dynamics when bilateral actions interfere: FMRI evidence for a network bottleneck
Motor system dynamics when bilateral actions interfere: FMRI evidence for a network bottleneck
Introduction:Producing even simple actions requires the coordinated interactions of distributed neural populations. Identifying the functional roles of these dynamic motor network interactions, both in health and disease, poses an important challenge (Grefkes & Fink 2011). Here, we investigated...
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Personal Name(s): | Viswanathan, Shivakumar (Corresponding author) |
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Abdollahi, Rouhollah / Wang, Bin / Daun, Silvia / Fink, Gereon Rudolf / Grefkes, Christian | |
Contributing Institute: |
Kognitive Neurowissenschaften; INM-3 |
Imprint: |
2016
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Conference: | 22nd OHBM Annual Meeting, Genf (Schweiz), 2016-06-26 - 2016-06-30 |
Document Type: |
Abstract |
Research Program: |
(Dys-)function and Plasticity |
Publikationsportal JuSER |
Introduction:Producing even simple actions requires the coordinated interactions of distributed neural populations. Identifying the functional roles of these dynamic motor network interactions, both in health and disease, poses an important challenge (Grefkes & Fink 2011). Here, we investigated the function-dynamics relationship in the production of stimulus-synchronized periodic hand movements, where neural events evoked by each stimulus and its synchronized movement occur almost simultaneously but have a complex indirect functional relationship. To disentangle the motoric elements of this functional relationship from other general anticipatory processes, we used a novel bilateral interference paradigm to selectively perturb motor system dynamics.Methods:Participants produced periodic index-finger movements synchronized with periodic visual stimuli (2.2Hz) over 28 second blocks. In each block, an instruction cue indicated whether responses were required with (i) the right hand only; (ii) the left hand only; (iv) both hands together; or (iii) alternating between hands. Importantly, the stimuli had color cues so that movements were produced in cycles of 4 consecutive movements alternating with a pause for 4 consecutive stimuli. FMRI and EEG data were obtained from 23 healthy young participants who performed this task in separate counterbalanced sessions. Only FMRI results are reported here. BOLD signal dynamics were analyzed using z-scored raw BOLD time-series from volumes of interest in the core motor network in both hemispheres, namely, M1, dorsal and ventral premotor cortices, SMA, and an anterior and posterior cluster along the intra-parietal sulcus. Dynamic causal modeling (DCM) was used to estimate interaction strengths between these regions in each hemisphere.Results:The task demand for intermittent responses robustly perturbed synchronization performance. For unilateral responses, the mean response time relative to stimulus onset systematically decreased from the first to the fourth stimulus consistent with a sensorimotor calibration process. Remarkably, this timing change was amplified when both hands were moved together; and was abolished when producing movements by alternating hands. While the changes in relative timing were identical for right and left hand responses, the absolute timing differed between hands and was consistent with a process dominated by right hand responses. Brain dynamics showed substantial inter-hemispheric differences. BOLD signal dynamics in PMv, PMd, SMA and posterior-IPS differed between conditions in the left hemisphere but not in right hemisphere. The DCM connection strengths showed a greater influence of the anterior IPS on SMA and PMv in the left hemisphere, while SMA had a greater influence on PMv in the right hemisphere.Conclusions:Studies of sensorimotor synchronization have typically focused on processes linked to stimulus timing (i.e., the "rhythm"). Our results demonstrate the crucial additional role of motor constraints in producing stimulus-synchronized movements. These constraints are consistent with a functional "bottleneck" that limits the ability to simultaneously calibrate the movements of multiple effectors. Specifically, when moving both hands together, the calibration of left hand movements were dominated by the state of the right hand. The absence of calibration when alternating movements suggests that the bottleneck constrains the ability to switch between calibrating independent effectors. The presence of dynamic perturbations in the left but not right hemisphere, suggest that rather than being one specific region in the brain, this "bottleneck" may be the outcome of dynamic conflicts in the motor network. |