EEG signatures of arm isometric exertions in preparation, planning and execution

Abstract

The electroencephalographic (EEG) activity patterns in humans during motor behaviour provide insight into normal motor control processes and for diagnostic and rehabilitation applications. While the patterns preceding brisk voluntary movements, and especially movement execution, are well described, there are few EEG studies that address the cortical activation patterns seen in isometric exertions and their planning. In this paper, we report on time and time-frequency EEG signatures in experiments in normal subjects (n=8), using multichannel EEG during motor preparation, planning and execution of directional centre-out arm isometric exertions performed at the wrist in the horizontal plane, in response to instruction-delay visual cues. Our observations suggest that isometric force exertions are accompanied by transient and sustained event-related potentials (ERP) and event-related (de-)synchronisations (ERD/ERS), comparable to those of a movement task. Furthermore, the ERPs and ERD/ERS are also observed during preparation and planning of the isometric task. Comparison of ear-lobe-referenced and surface Laplacian ERPs indicate the contribution of superficial sources in supplementary and pre-motor (FC z ), parietal (CP z ) and primary motor cortical areas (C 1 and FC 1 ) to ERPs (primarily negative peaks in frontal and positive peaks in parietal areas), but contribution of deep sources to sustained time-domain potentials (negativity in planning and positivity in execution). Transient and sustained ERD patterns in μ and β frequency bands of ear-lobe-referenced and surface Laplacian EEG indicate the contribution of both superficial and deep sources to ERD/ERS. As no physical displacement happens during the task, we can infer that the underlying mechanisms of motor-related ERPs and ERD/ERS patterns do not only depend on change in limb coordinate or muscle-length-dependent ascending sensory information and are primary generated by motor preparation, direction-dependent planning and execution of isometric motor tasks.The results contribute to our understanding of the functions of different brain regions during voluntary motor tasks and their activity signatures in EEG can shed light on the relationships between large-scale recordings such as EEG and other recordings such as single unit activity and fMRI in this context.

The Dynamic Dielectric at a Brain Functional Site and an EM Wave Approach to Functional Brain Imaging

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Visuomotor Control of Ankle Joint using Position vs. Force

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“…Some neurophysiological differences between lower and upper limb suggest that the performance of tasks involving visuomotor coordination may be different in ankle: (1) The neuro-circuitries for individuated digit control are evolved differently in lower vs. upper limbs (Hashimoto et al, 2013), (2) the H-reflex responses in lower limb are different from those in upper limb (Zehr, 2002), and (3) altering the cutaneous feedback through electrical stimulation affects the performance in visuomotor ankle forcematching, but not the position-matching tasks (Choi et al, 2013). Among similarities, the system-level neurophysiological signatures such as motor-related cortical potential are present for both upper limbs (Waldert et al, 2009;Nasseroleslami et al, 2011aNasseroleslami et al, , 2011bNasseroleslami, Lakany, et al, 2014) and lower limbs (Nascimento et al, 2006;Nascimento & Farina, 2008) in position and force control. From a neurophysiological perspective, the complex differences between the upper and lower extremity limit the generalization of the previous findings in upper limb (negligible to some degree advantage for force control) to the lower extremity and ankle joint.…”

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