Immediate effect of neurofeedback in passive BCI for alertness control

We develop a passive brain-computer interface (BCI) which uses neurofeedback to maintain a high level of attention during the accomplishment of a prolonged task. The attention degree is estimated from EEG signals using methods of nonlinear and statistical time-frequency analyses. We find that the feedback increases the duration of the maximum interval during which the subject maintains substantial attention (150±40 s with feedback versus 100±20 s without feedback). However, the mean degree of attention during this interval is 27% lower than without feedback. The obtained result evidences that the cognitive reserve is limited, and therefore, to maintain high performance for a prolonged time, the brain operates in a “safe-mode” regime.