Distinct cortical correlates of perception and motor function in balance control

Fluctuations in brain activity alter how we perceive our body and generate movements but have not been investigated in functional whole-body behaviors. During reactive balance, we recently showed that evoked brain activity is associated with balance ability in young individuals. Further, in Parkinson's disease, impaired whole-body motion perception in reactive balance is associated with impaired balance. Here we investigated brain activity during whole-body motion perception in reactive balance in young adults (9 female, 10 male). We hypothesized that both ongoing and evoked cortical activity influence the efficiency of information processing for successful perception and movement during whole-body behaviors. We characterized two cortical signals using electroencephalography localized to the supplementary motor area: 1) the “N1”, a perturbation-evoked potential that decreases in amplitude with expectancy and is larger in individuals with lower balance function; 2) pre-perturbation beta power, a transient rhythm that favors maintenance of the current sensorimotor state and is inversely associated with tactile perception. In a two-alternative forced choice task, participants judged whether pairs of backward support-surface perturbations during standing were in the “same” or “different” direction. As expected, lower whole-body perception was associated with lower balance ability. Within a perturbation pair, N1 attenuation was larger on correctly perceived trials and associated with better balance, but not perception. In contrast, pre-perturbation beta power was higher on incorrectly perceived trials and associated with poorer perception, but not balance. Together, ongoing and evoked cortical activity have unique roles in information processing that give rise to distinct associations with perceptual and balance ability. Significance statement Fluctuations in ongoing and evoked brain activity with identical sensory stimuli can give rise to different perceptual and motor outcomes. Such dynamic information processing is necessary for successful sensorimotor control in nonmobile tasks, but has not been investigated in perception and movement in functional whole-body behaviors. Here we show that perception and balance have distinct neural correlates; pre-perturbation activity was associated with better perception whereas perturbation-evoked activity was associated with better balance. Our results support the hypothesis that both ongoing and evoked cortical activity during functional whole-body tasks contributes to successful perception and movement.