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.

Toward passive BCI: asynchronous decoding of neural responses to direction- and angle-specific perturbations during a simulated cockpit scenario.

Neuroimaging studies have provided proof that loss of balance evokes specific neural transient wave complexes in electroencephalography (EEG), called perturbation evoked potentials (PEPs). Online decoding of balance perturbations from ongoing EEG signals can establish the possibility of implementing passive brain-computer interfaces (pBCIs) as a part of aviation/driving assistant systems. In this study, we investigated the feasibility of identifying the existence and expression of perturbations in four different conditions by using EEG signals. Fifteen healthy participants experienced four various postural changes while they sat in a glider cockpit. Sudden perturbations were exposed by a robot connected to a glider and moved to the right and left directions with tilting angles of 5 and 10 degrees. Perturbations occurred in an oddball paradigm in which participants were not aware of the time and expression of the perturbations. We employed a hierarchical approach to separate the perturbation and rest, and then discriminate the expression of perturbations. The performance of the BCI system was evaluated by using classification accuracy and F1 score. Asynchronously, we achieved average accuracies of 89.83 and 73.64% and average F1 scores of 0.93 and 0.60 for binary and multiclass classification, respectively. These results manifest the practicality of pBCI for the detection of balance disturbances in a realistic situation.

A novel hybrid BCI speller based on RSVP and SSVEP paradigm.

BACKGROUND AND OBJECTIVE: Steady-state visual evoked potential (SSVEP) and rapid serial visual presentation (RSVP) are useful methods in the brain-computer interface (BCI) systems. Hybrid BCI systems that combine these two approaches can enhance the proficiency of the P300 spellers. METHODS: In this study, a new hybrid RSVP/SSVEP BCI is proposed to increase the classification accuracy and information transfer rate (ITR) as compared with the other RSVP speller paradigms. In this paradigm, RSVP (eliciting a P300 response) and SSVEP stimulations are presented in such a way that the target group of characters is identified by RSVP stimuli, and the target character is recognized by SSVEP stimuli. RESULTS: The proposed paradigm achieved accuracy of 93.06%, and ITR of 23.41 bit/min averaged across six subjects. CONCLUSIONS: The new hybrid system demonstrates that by using SSVEP stimulation in Triple RSVP speller paradigm, we could enhance the performance of the system as compared with the traditional Triple RSVP paradigm. Our work is the first hybrid paradigm in RSVP spellers that could obtain the higher classification accuracy and information transfer rate in comparison with the previous RSVP spellers.