doi.org
Cortico-muscular control of postural balance in older adults – effects of training on functional connectivity
Background Balance training in older adults can lead to reduced centre of mass accelerations and reduced angular momenta after perturbations of unipedal stance, reflecting an enhanced ability to recover balance. It has been suggested that the co-occurring changes in muscle synergies indicated strategy-specific adaptations in feedback control. Methods We investigated the cortical involvement in such adaptations by focusing on the interaction between muscle synergies and cortical activity after perturbations. Twenty older adults (>65 years) underwent short-term and three-week long-term balance training, and we assessed their recovery from unpredictable mediolateral perturbations during unipedal stance. We measured high-density EEG and activation of leg and trunk muscles. The representations of the balance-related muscle synergies were localised in the cortex using coherence-based beamformers in the β-frequency band. Results Balance performance was accompanied by task-specific β-band activation in the somatotopic representation of the lower extremities in the primary motor cortex. The β-power significantly dropped during the response to perturbations, while the coherence with the activation of muscle synergies significantly increased, especially for synergies active in the early stage of balance recovery. The task-related changes in cortico-synergy coherence, especially during the later phase of balance recovery, were significantly affected by short-term training. Conclusion Refinements of feedback control seem to underlie balance improvements in older adults. The significant changes in the cortico-synergy interaction after balance training suggest cortical involvement in these refinements. ### Competing Interest Statement The authors have declared no competing interest. European Union’s Horizon 2020, Marie Skłodowska-Curie grant agreement No 721577 European Research Council, European Union’s Horizon 2020 Research and Innovation Program grant agreement number 715945 Learn2Walk
