Brain-computer interface for estimation and control of alertness.

<p>(a) Schematical illustration of the experimental setup. (b) Control characteristics <i>G</i>_1,2,3(<i>t</i>) describing the degree of alertness during the processing of visual stimuli, obtained from three subjects of the group. The vertical dashed lines indicate the moments of time when the external disturbance (<i>t</i>_<i>EP</i>) was applied and the feedback message about the attention decrease (<i>t</i>_<i>FB</i>) was sent. The horizontal dash-dotted lines indicate the values of , , calculated by averaging <i>G</i>_1,2,3(<i>t</i>) over time intervals <i>t</i> < <i>t</i>_<i>EP</i>, <i>t</i>_<i>EP</i> > <i>t</i> > <i>t</i>_<i>FB</i> and <i>t</i> > <i>t</i>_<i>FB</i>. (c) Values of , and averaged over the group of eight subjects. The error bars indicate the standard deviation of these values among all participants.