Balance perturbation and error processing elicit distinct brain dynamics

Objective. The maintenance of balance is a complicated process in the human brain, which involves multisensory processing such as somatosensory and visual processing, motor planning and execution. It was shown that a specific cortical activity called perturbation-evoked potential (PEP) appears in the electroencephalogram (EEG) during balance perturbation. PEPs are primarily recognized by the N1 component with a negative peak localized in frontal and central regions. There has been a doubt in balance perturbation studies whether the N1 potential of perturbation is elicited due to error processing in the brain. The objective of this study is to test whether the brain perceives postural instability as a cognitive error by imposing two types of perturbations consisting of erroneous and correct perturbations. Approach. We conducted novel research to incorporate the experiment designs of both error and balance studies. To this end, participants encountered errors during balance perturbations at rare moments in the experiment. We induced errors by imposing perturbations to participants in the wrong directions and an erroneous perturbation was considered as a situation when the participant was exposed to an opposite direction of the expected/informed one. In correct perturbations, participants were tilted to the same direction, as they were informed. We analyzed the two conditions in time, time-frequency, and source domains. Main results. We showed that two error-related neural markers were derived from the EEG responses, including error positivity (Pe), and error-related alpha suppression (ERAS) during erroneous perturbations. Consequently, early neural correlates of perturbation cannot be interpreted as error-related responses. We discovered distinct patterns of conscious error processing; both Pe and ERAS are associated with conscious sensations of error. Significance. Our findings indicated that early cortical responses of balance perturbation are not associated with neural error processing of the brain, and errors induce distinct cortical responses that are distinguishable from brain dynamics of N1 potential.