Xenia J. Kozlov
Sleep is a state of brain activity when conscious experience, voluntary muscle movements and sensory activity is reduced or absent. There are two main stages of sleep, known as the Rapid Eye Movement (REM) when brain activity is more similar to awaken brain, and consciousness is reduced, being expressed through unusual sounds, visions, situations, etc., and the Slow Wave Sleep (SWS) when neurons get more synchronized and consciousness is absent. Each of these states is crucial for memory and learning processes; thus REM creates a new neural environment, mostly within the hippocampus, for a synaptic remodeling, which is important for learning and cognition, and during SWS, the synchronized neural reactivation of neurons of hippocampus and prefrontal cortex works for conversion short-term memory traces into long-term engrams (Clifton et al., 2015; Poe, Walsh & Bjorness, 2010). In other words, sleeping is crucial for memory storage (McDermott & Roediger, 2019).
Though causal relationships between lack of sleeping (insomnia) and memory impairment remain controversial, the existence of the correlation between these factors is clear. Studies show that people who suffer from insomnia (particularly, primary insomnia, or PI) are more likely to have cognitive problems, mainly problems with consolidation of declarative memory due to inability to transfer from hippocampus to prefrontal cortex (Canadian Longitudinal Study on Aging [CLSA], 2019; Nordqvist, 2013). Indeed, studies showed the strong associations between hippocampal volume decrease, or bilateral atrophy, and PI comparing to control groups (Riemann et al., 2007; Noh et al., 2012).
Sleep problems were observed in patients with ADHD for a comparatively long time, being mentioned in the DSM-III but instead of PI mostly related to elderly ages, scholars note the initial insomnia (II) which is characterized by problems with falling asleep. Some scholars suggest hypothesis that particular groups of patients with ADHD may suffer from PI as well, but the problem is that the symptoms of PI may mimic ADHD, so the final diagnosis in these cases is unclear (Weiss et al., 2006). However, patients with ADHD have worse sleeping comparing to neurotypical individuals, and here we can see the double-edged sword: on one hand, ADHD refers to the low focus, inattentiveness and forgetfulness due to the dysfunctions in the prefrontal region, basal ganglia, and parietal lobe (Curatolo, D'Agati & Moavero, 2010), and on the other hand, insomnia as a complication of ADHD impairs hippocampus and prefrontal cortex, which in its turn impairs memory storage.
As for the actual mechanisms of relationship between insomnia and ADHD, there are several versions, and each of them may be valid. Thus, insomnia may be a side effect of stimulants which are usually prescribed for hyperactive patients, or the syndrome of restless legs could work as a missing part in a puzzle; the delayed evening increase of melatonin and excessive motor activity are also listed (Konofal, Lecendreux & Cortese, 2010).
Among treatments for insomnia within hyperactivity, both sleep hygiene, melatonin and particular pharmaceuticals are listed (Weiss et al., 2006), so the treatment can be varied dependently on individual case. According to my own experience, the white noise as a cover for distracting stimuli and bedtime reading as a way to concentrate on non-reality topics and thus to distract from buzzling thoughts showed themselves as effective remedies. Probably, the effectiveness of bedtime reading as a remedy for insomnia could be connected through saccadic eye movements which are present both during reading and during the REM sleep stage.
Canadian Longitudinal Study on Aging [CLSA] (2019). Chronic insomnia alters the cognitive function of people aged 45 and over. Retrieved from https://nouvelles.umontreal.ca/article/2019/05/15/l-insomnie-chronique-altere-les-fonctions-cognitives-des-personnes-de-45-ans-et-plus/
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