The Neural Contributions to Reactive Balance Control: A Scoping Review of EEG, fNIRS, MRI, and PET Studies

Background/Objectives: Rapid postural reactions are critical for preventing falls, yet the neural systems supporting these responses are not fully understood, particularly with respect to aging and neurological disorders. Understanding how the brain detects, interprets, and responds to balance disturbances is essential for developing new interventions. This scoping review aimed to synthesize evidence from neuroimaging studies to identify the cortical and subcortical mechanisms underlying reactive balance and to characterize how these mechanisms are altered by aging and pathology. Methods: A structured search of EMBASE, PubMed, and CINAHL (7 November 2024) identified studies examining neural activity during experimentally induced balance perturbations. Sixty-one studies met inclusion criteria (EEG n = 45; MRI n = 9; fNIRS n = 8; PET n = 1) and were analyzed for patterns of regional activation and age- or disease-related differences. Results: Evidence converges on a distributed network supporting reactive balance. Sensorimotor, premotor, supplementary motor, and prefrontal cortices show consistent involvement, while cerebellar, brainstem, and basal ganglia structures contribute to rapid, automatic responses. Aging and neurological conditions commonly heighten cortical activation, suggesting reduced automaticity and increased reliance on compensatory control. Conclusions: Reactive balance emerges from coordinated activity across cortico-subcortical systems that are altered by aging and pathology. Further research incorporating multimodal imaging approaches and more ecologically realistic perturbation paradigms is needed to clarify mechanistic pathways and inform precision-based fall-prevention strategies.