Reliable predictors of SMR BCI performance — Do they exist?

Reliable predictors of BCI performance would be desirable for basic research and application of BCI in a clinical context alike. In basic research, predictors help to elucidate how the brain instantiates BCI control. With respect to BCI controlled applications to be used by patient end-users with disease, predictors could support the choice of the optimal brain signal. Training of the predicting variable may support later BCI control. Among others, physiologic and psychologic variables have been suggested as such predictors. For example, the resting state μ-rhythm peak, the activation of dorsolateral prefrontal cortex during motor imagery, and the ability to coordinate visual and motor information were related to performance in different motor imagery BCI paradigms. The predictive power was low to medium, few even high, where the physiologic predictor was most powerful. To identify predictors, those and the related criterion variable have to be unambiguously defined. Likewise, reliability and validity have to be specified in the realm of BCI.