cortical thickness is a common measure of brain maturation; the main difference in children with adhd shows a delay in cortical thickness, specifically in the frontal lobe. significant correlations in the trajectory of gray matter thickness and swa suggest that swa may be able to indicate levels of cortical maturation on an individual level. however, there has yet to be a study in which the diagnosis of adhd can be given directly from swa readings. memory non-rapid eye movement sleep is known for its beneficial effect on memory consolidation, especially for declarative memory (while procedural memory improvement is more associated with rem-sleep), even if it is important to note that a clear-cut distinction between stages' influence on type of learning doesn't seem to be possible. generally, both rem and nrem are associated with an increased memory performance, because newly encoded memories are reactivated and consolidated during sleep. nrem sleep has been demonstrated to be intimately correlated with declarative memory consolidation in various studies, where subject slept after a declarative memory-task; these who had a sleep imbued of nrem stages, had a better performance after the nap or the night, compared to subjects who have been awake or had more rem-sleep. the importance of nrem sleep in memory consolidation has also been demonstrated using cueing; in this paradigm, while participants are sleeping and are in nrem sleep stages, cues are proposed (which can be, for example, aurally-presented sounds or words, odors, and so on). the fact that this procedure was effective on the improvement of the later memory performance, indicates that during these stages, there is a reactivation of the memory traces and a subsequent consolidation, which are facilitated by the cues; importantly, this doesn't work if the cueing is presented when subjects are awake or in rem stages. furthermore, the specific and crucial role of sws (slow-wave sleep, a stage of nrem sleep) in memory consolidation has been demonstrated in a study where, through electrical stimulations, slow oscillations were induced and boosted; because of this swa increase, participants had a better performance in declarative memory tasks. not only swa helps learning, but it is also crucial, because its suppression has been demonstrated to impair declarative memory consolidation. on the other hand, sleep spindles (especially associated with n2 nrem sleep stage, but can also occur during n3 nrem sleep stage) are also crucial for declarative consolidation; indeed they are enhanced (increasing in density) after declarative learning, their increase is associated with a better memory performance (which has been proved using pharmacological manipulation of spindles' density, and measuring outcomes on learning tasks). a working model of sleep and memory stabilization schreiner and rasch (2017) proposed a model illustrating how the cueing beneficial effect on memory during sleep could function, which includes theta and gamma waves and sleep spindles. increased theta activity represents the successful reestablishment of the memory after the cueing: if such an increase is observed, it means that the association between the cue and the memory trace is strong enough, and that the cue is presented in an effective way and time. theta waves interacts with gamma activity, and - during nrem - this oscillatory theta-gamma produces the relocation of the memory representation, from the hippocampus to the cortex. on the other hand, sleep spindles increase occurs right after or in parallel to the theta augmentation, and is a necessary mechanism for the stabilization, the reinforcement and also the integration of the newly encoded memory trace. importantly, in this working model, slow oscillations have the role of a 'time-giving pace maker', and seem to be a prerequisite for the success of cueing. according to this model, enhancing only slow waves or only spindles, is not sufficient to improve memory function of sleep: both need to be increased to obtain an influence and this latter. nrem in other animals not much is known about nrem, so scientists have conducted studies in other animals to potentially understand more, in particular why the brain has evolved to have two distinct states. in their studies, it was found that between birds and certain mammals like dolphins, their brains exhibit similar behavior. it was found that certain species of birds have half their brain's hemisphere release brain waves similar to a human's during nrem sleep, and the other half of it fully conscious, allowing them to fly while sleeping. certain species of dolphins also exhibit similar behavior as birds in order to be able to swim while sleeping. in rats, after a 24-hour sleep deprivation, it was found that there was an increase of slow-wave activity in nrem sleep, which corresponds directly with the human brain which when sleep deprived, prioritizes nrem sleep over rem sleep, implying that the nrem sleep is responsible for regulating and compensating for missed sleep.