Error-related potential (ErrP)

The error-related potential is an event-related response generated over fronto-central cortex when the outcome a person perceives conflicts with what they intended or expected. Its components are an early error-related negativity (often peaking within about 100 ms of the eliciting event, thought to originate near the anterior cingulate) followed by a later error positivity (Pe) associated with conscious error awareness. Crucially for BCI, an ErrP is evoked not only by the user's own mistakes but by mistakes the machine makes on the user's behalf — a mis-selected letter, a cursor that moves the wrong way — which makes it a readable signal of when the interface has erred.

This opens two uses: detecting BCI errors on individual actions so they can be vetoed or corrected, and providing an intrinsic teaching signal for adaptation. Both are constrained by the fact that single-trial ErrP detection is imperfect (reported accuracies commonly in the seventies to low nineties percent) and that the ErrP is itself a second signal to decode, with its own non-stationarity and its own latency between the error and a confident detection. Feedback-observation ErrPs also differ in morphology and reliability from ErrPs to one's own executed errors.