Feedback processing as parallel task in P300 conditioning

Abstract

Previous reports on conditioning P300 amplitude indicated that downtraining produced a stronger effect than uptraining. This asymmetry can be due to the effect of drain on processing resources of the brain produced by the attempts to use feedback information (parallel task effect). Such a drain should reduce P300 amplitude regardless of the direction of training. The aim of the experiment was to demonstrate this effect. Event-related potentials (ERPs) evoked by light stimuli in a standard odd-ball procedure were recorded from Fz, Cz and Pz scalp sites. Subjects were instructed to enlarge or to reduce the P300 amplitude. The first 30 presentations of the target stimulus were analyzed during which the effect of learning should be negligible and processing of feedback information should be intensive. ERPs recorded during uptraining and downtraining were compared with the no-feedback recordings. As predicted, downtraining significantly reduced the P300 amplitude even in the first session oflearning. Unexpectedly, uptraining recordings did not differ from no-feedback ERPs but differed significantly from downtraining waves. Such results support the prediction that feedback procedures involve a number of processes that alter the P300 amplitude even before the effects of learning can be expected. But if the hypothesis of the parallel task is to be accepted there must be another instantaneous process that compensates for P300 amplitude reduction during uptraining.