NREM

Non-rapid eye movement (NREM) sleep is a sleep stage marked by high delta power in an EEG. The slow wave delta oscillations primarily arise from the prefrontal cortex.

For a discussion of REM-NREM sleep switching model see Sleep section.

Plasticity/Learning
There's strong evidence that sleep contributes to consolidation of new memories, but the role of NREM (or an particular stage of sleep) is unclear. Using transcranial electrodes, a study potentiated slow wave oscillations in frontal cortex of humans and increased memory recall. Early stages of NREM sleep increase procedural memory. This might be NREM specific, as pharmacological blockade of REM sleep did not similarly impair procedural memory.
 * Some data from cat suggests that NREM rhythm could lead to NMDA-dependent LTP-like potentiation, however the data is not that compelling.
 * One study found that L5 somatosensory cells have decreased membrane-bound calcium permeable AMPARs at the end of the light period (when animals are presumably sleeping more). They use a correlational slice paradigm, relying on sleep's circadian rhythm. Inducing paired bursts (eEPSPs with a subsequent short burst +10 ms) as a way of mimicking a slow-wave bursting environment led to a fairly similar and strong reduction in these AMPARs in addition to calcium impermeable AMPARs likely via a PKC mechanisms. This form of LTD could also be induced with elicited bursts alone. The design of the study does confound circadian time and sleep.