Abstract

Balance control is a fundamental component of human every day motor activities such as standing or walking, and its impairment is associated with an increased risk of falling. However, in humans the exact neurobiological mechanisms underlying balance control are still unclear. Specifically, although previous studies have identified a number of cortical regions that become significantly activated during real or imagined balancing, the interactions within and between the relevant cortical regions remain to be investigated. The working hypothesis of this study is that cortical networks contribute to an optimization of balance control, and that this contribution can be revealed by partial directed coherence—a time-variant, frequency-selective and directed functional connectivity analysis tool. Electroencephalographic activity was recorded in 37 subjects during single-leg balancing on a stable as well as an unstable surface. Results of this study show that in the transition from balancing on a stable surface to an unstable surface, two topographically delimitable connectivity networks (weighted directed networks) are established; one associated with the alpha and one with the theta frequency band. The theta network sequence can be described as a set of subnetworks (modules) comprising the frontal, central and parietal cortex with individual temporal and spatial developments within and between those modules. In the alpha network, the occipital electrodes O1 and O2 act as a source, and the interactions propagate predominantly in the directions from occipital to parietal and to centro-parietal areas. These important findings indicate that balance control is supported by at least two functional cortical networks.

Highlights

  • Andreas Mierau and Britta Pester have contributed to this study.Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Balance control is a fundamental component of human every day motor activities such as standing or walking, and its impairment is associated with an increased risk of falling

  • The grand mean amplitude-time–frequency maps (TFMs) of activity showed strong theta oscillations at about 6 Hz (e.g. CPz) and alpha oscillations at 10 Hz

  • For the electrodes CPz and Pz (5–8 s) as well as Cz, C1, CP1, CP2 (5–6 s) the mean theta amplitude significantly increased during balancing on an unstable surface (BUS) compared to balancing on a stable surface (BSS)

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Summary

Introduction

Andreas Mierau and Britta Pester have contributed to this study. Balance control is a fundamental component of human every day motor activities such as standing or walking, and its impairment is associated with an increased risk of falling. Controlling posture and balance requires a complex interplay within and between the sensory and the motor systems. Animal preparation studies suggest upright posture and balance are predominantly controlled by neural circuits in the spinal cord, the brainstem and the cerebellum. We used electroencephalography (EEG) to identify cortical regions that become activated during a wide range of continuous standing balance tasks differing in difficulty by changing the base of support, surface stability, or both (Hülsdünker et al 2015),

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