[Biofeedback of slow brain potentials]

Slow cortical potentials constitute neurophysiological indicators of cortical excitability. Behaviorally they correlate with attention and motor preparation. A system for biofeedback and self-regulation of slow cortical potentials (SCP) has been developed. The portable system allows on-line visual feedback of filtered and corrected slow brain potentials in a predetermined sequence of trials. Three different algorithms for transforming the original SCP-signal into a feedback-signal have been developed and were compared in a controlled outcome study. With the optimal feedback method subjects were able to produce cortical positivity and negativity on command after three sessions. Increases and decreases of negativity of up to 20 microV were also achieved. Therefore a simple and portable PC-based device for the clinical application of SCP-biofeedback is now available.