Memory consolidation

The functions of these different phases of sleep are not at all clear but chronic sleep deprivation does eventually lead to death. It seems to be the slow-wave component of sleep (SWS) that is vital and it is thought to serve a restorative purpose. This would be consistent with its greater occurrence during the early stages of the sleep cycle when hormone secretion supports anabolic metabolism. If subjects are wakened every time they enter a period of REM sleep (evidenced by the EEG) there appears to be no overt harmful effect on their behaviour. In fact, REM sleep deprivation has even been used, with some claims of success, as a treatment for minor depression. However, there is an unproven belief that REM sleep is important for memory consolidation. 

Stickgold, R. (2005). Sleep-dependent memory consolidation. Nature 437, 1272-8. 

Podol skii IYa, Kondrat eva EV, Shcheglov IV et al. (2002) Fullerene C60 complexed with poly(N-vinylpyrrolidone) prevents the disturbance of long-term memory consolidation. Phys Solid States. 44 552-554. 

Opioid effects on memory are consistent in humans and animal models (Braida et al. 1994 Saha et al. 1991). Verbal and visual memory are impaired by morphine one hour after oral administration (Hanks et al. 1995 Kerr et al. 1991). These could be due to direct neuronal effects of opioids, or perhaps through indirect effects on cholinergic transmission. However, in some animal paradigms morphine can enhance memory consolidation through indirect dopaminergic mechanisms (Castellano et al. 1994). 

Cestari V, Castellano C. (1996). Caffeine and cocaine interaction on memory consolidation in mice. Arch Int Pharmacodyn Ther. 331(1) 94-104. 

Castellano C, Cabib S, Palmisano A, Di Marzo V, Puglisi-Allegra S. (1997). The effects of anandamide on memory consolidation in mice involve both Dl and D2 dopamine receptors. Behav Pharmacol. 8(8) 707-12. 

McGaugh JL, McIntyre CK, Power AE. 2002. Amygdala modulation of memory consolidation interaction with other brain systems. Neurobiology of Learning Memory... 

McIntyre CK, Power AE, Roozendaal B, McGaugh JL. 2003c. Role of the basolateral amygdala in memory consolidation. Ann NY Acad Sci 985 273-293. 

Roozendaal B. 2002. Stress and memory opposing effects of glucocorticoids on memory consolidation and memory retreival. Neurobiol Learn Mem 78(3) 578-595. 

Lynch WJ, Roth ME, et al (2002) Biological basis of sex differences in drug abuse preclinical and chnical studies. Psychopharmacology 164(2) 121-137 Mangan GL, Golding IF (1983) The effects of smoking on memory consolidation. 1 Psychol 115 65-77... 

AD subjects have a higher prevalence of sleep disturbances than normal elderly, including sleep fragmentation, advancement of the sleep-wake cycle, and decreased amounts of slow wave and rapid-eye movement (REM) sleep (Prinz et al., 1982 Reynolds et al., 1988 Bliwise et al., 1989). Sleep-wake cycle disruption in AD has been associated with a greater burden of neuropsychiatric disturbances (Rebok et al., 1991 Ancoli-Israel et al., 1994), particularly apathy and delusions (Kaufer et al., 2001). Several studies have observed a relationship between the degree of intellectual impairment and REM sleep abnormalities (Prinz et al., 1982 Vitiello et al., 1984 Moe et al., 1995), underscoring the role of REM sleep in memory consolidation (Wilson McNaughton, 1994). 

Tryptophan depletion in healthy volunteers impairs the retrieval of learnt material (Park et al., 1994), an effect probably mediated through a selective impairment of episodic memory consolidation (Riedel et al., 1999 Schmitt et al., 2000). However, tryptophan depletion appears to have no effect on working memory (Riedel et al., 1999) and either no effect or an enhancement of tests of executive function (Park et al., 1994 Schmitt et al., 2000). Thus the abnormality in episodic memory in mood disorders could conceivably be related to an impairment in the 5-HT system, but such an impairment is unlikely to account for the abnormalities in working memory and executive function. Clearly then, changes in consciousness occurring in affective disorders are unlikely to be explainable on the basis of an abnormality in a single neurochemical system. 

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