Activity in Functional Cortical Networks Temporally Associated with Postural Instability.

Human bipedal balance control is proposed to be the integrated activity of distributed neural areas. There is growing understanding about the cortical involvement in this highly automated behavior. While evidence exists for cortical activity temporally linked to reactive balance control, little is known about the functional interaction of potential cortical regions. Here, we used functional connectivity and graph theoretical analysis to derive functional cortical networks during reactive balance control from an event-related potential evoked by external perturbation known as the perturbation-evoked potential N1 (PEP N1). Fourteen healthy young adults were subjected to temporally unpredictable postural perturbations using a custom-made lean and release cable system. Electroencephalographic signals were recorded using a 64-channel electrode cap and segmented around perturbation onset. Functional connectivity was analyzed in source-space and sensor-space using coherence measures and functional cortical networks were characterized using graph measures. The results suggest that there might exist a balance control cortical network while standing and rapid, transient, and frequency-specific reorganization occurs in this network during reactive balance control events. This reorganization was characterized by an increased number of short-range connections between neighboring areas and increased strength between connections in delta, theta, alpha, and beta frequency bands during PEP N1 compared to baseline. To our knowledge, this is the first study to report the existence of functional cortical networks during reactive balance control with potential implications on assessing impaired balance associated with various neural diseases.