Learning and Sleep: examining the N1-P2 response after a daytime nap

Certain consolidation processes are considered sleep-dependent, meaning the success of a memory being stabilized into long-term storage is hypothesized to rely on, and occur partially during, sleep. Different types of learning may be affected differently by sleep, as they involve different processes and regions of the brain. In generalized learning, stimuli are mapped onto existing schemas, allowing prior knowledge to inform real-time perception. EEG recording allows a comparison of neural activity to behavioral measures of learning. The N1-P2 complex derived from a computed ERP is a reliable response to sound and may represent aspects of the neural encoding of its different features, changing as a function of learning. Such changes during wake may be a consequence of generalization alone, not consolidation, and it is unclear whether one sleep cycle is sufficient to produce the N1-P2 changes as seen in waking learning. The present study tested whether N1-P2 changes are seen in a wake control and nap group following generalized training and whether these changes diminish following a waking retention interval (to explain performance loss) or are restored after a nap and maintenance period (consolidation). We found a significant decrease in N1 and P2 accompanying performance improvement after training, and an increase in N1-P2 with performance loss after a waking interval. After a nap (or period of wake) both groups showed a decrease in N1 and a change in P2 that followed the direction of their performance change. An opportunity for a midday nap did not significantly predict later changes in N1 or P2. This neural response therefore may not be a driving force in performance of generalized learning; rather, it may change as a consequence of the way attention is directed. Further, a midday nap does not significantly affect neural activity or performance on a generalized perceptual auditory learning task.