Slow Cortical Potential

Gradual voltage shifts in the electrical activity of the brain, occurring over periods of several hundred milliseconds to several seconds. Slow cortical potentials reflect changes in the overall excitability level of cortical neural networks — negative shifts indicate increased cortical activation while positive shifts indicate reduced activation. In brain-computer interface systems, users can learn to voluntarily generate positive or negative slow cortical potential shifts to control binary selections or move a cursor. SCPs were among the earliest brain signals used for BCI communication, demonstrated by Niels Birbaumer and colleagues for enabling people with locked-in syndrome to spell words letter by letter.