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Menstrual cycle effects on sleep-dependent memory consolidation
... df = 29, p = 0.97). Females did not use any hormonal contraceptives and the experiments were scheduled in the mid-luteal phase of their menstrual cycle, in order to control for previously reported effects of menstrual cycle phase and hormonal contraceptives on sleep-dependent memory consolidation (Genzel et al. 2012(Genzel et al. , 2014. Further exclusion criteria were: medication, nightshifts for at least 8 wks before the experiment, sleep disturbances or irregular sleep-wake cycle, neurological or sleep-related diseases, being involved in the preparation of an imminent exam, and caffeine/alcohol intake on the experimental day. ...
Sleep fosters the generation of explicit knowledge. Whether sleep also benefits implicit intuitive decisions about underlying patterns is unclear. We examined sleep's role in explicit and intuitive semantic coherence judgments. Participants encoded sets of three words and after a sleep or wake period were required to judge the potential convergence of these words on a common fourth associate. Compared with wakefulness, sleep increased the number of explicitly named common associates and decreased the number of intuitive judgments. This suggests that sleep enhances the extraction of explicit knowledge at the expense of the ability to make intuitive decisions about semantic coherence.
Sex differences favoring women have been found in a number of studies of episodic memory. This study examined sex differences in verbal, nonverbal, and visuospatial episodic memory tasks. Results showed that although women performed at a higher level on a composite verbal and nonverbal episodic memory score, men performed at a higher level on a composite score of episodic memory tasks requiring visuospatial processing. Thus, men can use their superior visuospatial abilities to excel in highly visuospatial episodic memory tasks, whereas women seem to excel in episodic memory tasks in which a verbalization of the material is possible.
Posttraining rapid eye movement (REM) sleep has been reported to be important for efficient memory consolidation. The present results demonstrate increases in the intensity of REM sleep during the night of sleep following cognitive procedural/implicit task acquisition. These REM increases manifest as increases in total number of rapid eye movements (REMs) and REM densities, whereas the actual time spent in REM sleep did not change. Further, the participants with the higher intelligence (IQ) scores showed superior task acquisition scores as well as larger posttraining increases in number of REMs and REM density. No other sleep state changes were observed. None of the pretraining baseline measures of REM sleep were correlated with either measured IQ or task performance. Posttraining increases in REM sleep intensity implicate REM sleep mechanisms in further off-line memory processing, and provide a biological marker of learning potential.
We analyzed sex differences in spatial and recall abilities of college students while also examining the relationship to 2D:4D ratio. The 2D:4D ratio is thought to be an indirect measure of testosterone and estrogen exposure in fetal development. Participants completed a mental rotation (MR) test, free recall tests, and placement recall tests. It was predicted and confirmed that males have lower 2D:4D ratio and higher MR scores. Additionally, females outscored males on picture free recall and picture placement. Higher scoring females on these two measures had higher 2D:4D ratios, that is, more “feminine” looking hands. The results from our study are consistent with the hypothesis that fetal hormones affect 2D:4D ratio while also directly or indirectly influencing visual recall abilities in females. The tendency of sexually dimorphic cognitive skills to correlate with 2D:4D ratio in only one sex may be typical of traits that were evolutionarily adaptive in one sex, but not maladaptive in the opposite sex.
Human sleep is characterized by the cyclic occurrence of episodes of non-REM and REM sleep and by distinct secretory patterns of several hormones. During depression and aging there are similar changes in the neurophysiological and the neuroendocrine components of sleep. A review of data deriving from clinical studies in patients and controls and from animal research supports the view of a bidirectional interaction between sleep structure and nocturnal hormone secretion. These data suggest that changes in the activity of neurohormones have a key role in the development of aberrant sleep during depression and during aging.
Recall of paired-associate lists (declarative memory) and mirror-tracing skills (procedural memory) was assessed after retention intervals defined over early and late nocturnal sleep. In addition, effects of sleep on recall were compared with those of early and late retention intervals filled with wakefulness. Twenty healthy men served as subjects. Saliva cortisol concentrations were determined before and after the retention intervals to determine pituitary-adrenal secretory activity. Sleep was determined somnopolygraphically. Sleep generally enhanced recall when compared with the effects of corresponding retention intervals of wakefulness. The benefit from sleep on recall depended on the phase of sleep and on the type of memory: Recall of paired-associate lists improved more during early sleep, and recall of mirror-tracing skills improved more during late sleep. The effects may reflect different influences of slow wave sleep (SWS) and rapid eye movement (REM) sleep since time in SWS was 5 times longer during the early than late sleep retention interval, and time in REM sleep was twice as long during late than early sleep (p < 0.005). Changes in cortisol concentrations, which independently of sleep and wakefulness were lower during early retention intervals than late ones, cannot account for the effects of sleep on memory. The experiments for the first time dissociate specific effects of early and late sleep on two principal types of memory, declarative and procedural, in humans.
Prenatal gonadal hormones have been implicated as important factors in the development of different spatial abilities, including spatial navigation. The aim of the study reported here was to examine the relationship between navigational abilities and the second-to-fourth digit ratio (2D:4D ratio) in healthy women. There is evidence that the ratio of the length of second and fourth digits is negatively related to prenatal testosterone and positively positively related to prenatal estrogen. In this study, the 2D:4D ratio was measured in a sample of 46 female university students. The subjects' place learning ability was tested in a real arena maze (RAM). Our results tend to support an association between prenatal gonadal hormone concentration and some aspects of spatial navigation. The subjects with lower 2D:4D ratio had significantly longer hidden platform-finding latency, better spatial recall, and selected significantly more navigation cues in a posttest of the arena maze learning.
Early in development, steroid hormones structurally organize various regions of the CNS. However, steroid hormones continue to affect the structure and function of the CNS throughout the life of the individual. In this review, we discuss sex differences and similarities in steroid-induced synaptic plasticity in the adult brain. Particular emphasis is placed on steroid-induced plasticity in the hippocampus, a brain region important in learning and memory. This topic is relevant to the growing evidence for the actions of sex hormones outside of the reproductive neuroendocrine axis. It also tells an important and emerging story about non-genomic and genomic actions of steroids at the cellular and molecular levels. Specifically, the effects of estrogen and progesterone as well as the androgens and glucocorticoids are discussed. The influence of steroids on hippocampal structure and function can differ vastly between the sexes. However, there are certain similarities that might aid in our understanding of how steroids affect CNS plasticity in general. Although future studies will undoubtedly lead us to a greater understanding of these phenomena, the data reviewed indicate that when studying synaptic plasticity, the sex and hormonal milieu of the individual might significantly influence the outcome and interpretation of the research.
Steiger A (Max Planck Institute of Psychiatry, Munich, Germany). Sleep and endocrinology (Minisymposium). J Intern Med 2003; 254: 13–22.
A bidirectional interaction between sleep electroencephalogram and endocrine activity is well established in various species including humans. Various hormones (peptides and steroids) participate in sleep regulation. A keyrole was shown for the reciprocal interaction between sleep-promoting growth hormone-releasing hormone (GHRH) and sleep-impairing corticotropin-releasing hormone (CRH). Changes in the GHRH : CRH ratio result in changes of sleep-endocrine activity. It is thought that the change of this ratio in favour of CRH contributes to aberrances of sleep during ageing and depression (shallow sleep, blunted GH and elevated cortisol). Besides GHRH, ghrelin and galanin enhance slow wave sleep. Somatostatin is another sleep-impairing factor. Neuropeptide Y acts as a CRH antagonist and induces sleep onset. There are hints that CRH promotes rapid eye movement sleep (REMS). In animals prolactin enhances REMS. In humans vasocactive intestinal polypeptide (VIP) appears to play a role in the temporal organization of sleep as, after VIP, the non-REMS–REMS cycle decelerated. Cortisol appears to enhance REMS. Finally, gonadal hormones participate in sleep regulation. Oestrogen replacement therapy and CRH-1 receptor antagonism in depression are beneficial clinical applications of sleep-endocrine research.