Memory performance and area-specific self-regulation of slow cortical potentials: dual-task interference.

We examined the effect of area-specific feedback for slow potentials on sensorimotor and memory performance under single and dual-task conditions. Subjects observed a memory set for 400 ms and then determined 5 s later whether a target letter had been contained in the original presentation (Sternberg task). After one session of Sternberg-only training, feedback training was added for production of negative and positive slow potentials area-specifically at Fz, Cz or Pz during the 5-s interval separating the memory set and target probes. Addition of the feedback task resulted in an increase in Sternberg response latency and errors which was followed by gradual recovery over five dual-task sessions (recovery not complete for the error measure). Subjects successfully regulated their slow potentials, but only in an area-nonspecific fashion, even though area-specific control was observed in an earlier study under a feedback-only condition. Sternberg performance did not depend on whether slow potential negativity or positivity was produced. These findings indicate that competition between tasks was a more important determinant of performance than was modulation of dendritic polarization by feedback-induced slow potentials.