Fig. 2: Neurofeedback task and classification.

a Representative example for normalized and mixed firing rate during ten high (red) and ten low (blue) target tone frequency feedback trials of day 247. The patient was asked to match the target tone by modulating the normalized and weighted firing rate, and he succeeded in all but one trial of this example. Trials were completed as soon as the firing rate was held above or below the upper or lower threshold, respectively. As defined in the Materials and Methods section, these feedback blocks were performed every day of recording for training, parameter selection, and validation of the selected parameters. The grey-shaded region from −1 to 0 s depicts the time period during which the high or low target tones were presented to the patient. The horizontal line at 0.3 and 0.7 shows the lower and upper threshold, respectively. Source data are provided as a Source Data file. b True positive rate vs. false positive rate of the trials in auditory neurofeedback blocks directly preceding speller blocks on days 123–462. Each circle represents one neurofeedback block; circles are jittered for better visibility. The blue insert at the bottom right corner shows the contingency table of all neurofeedback trials directly preceding speller blocks on days 123–462. In the blue insert—TP stands for true positive, i.e., up trials classified as up; FP stands for false positive, i.e, up trials classified as down; FN—stands for false negative, i.e., down trials classified as up; TN—stands for true negative, i.e., down trials classified as down; Time out denotes the trials that were unclassified. Source data are provided as a Source Data file.