Neurosteroids in learning and memory processes.
ABSTRACT The discovery that neurosteroids could be synthesized de novo in the brain independent from the periphery and display neuronal actions led to great enthusiasm for the study of their physiological role. Pharmacological studies suggest that neurosteroids may be involved in several physiological processes, such as learning and memory. This chapter summarizes the effects of the administration of neurosteroids on learning and memory capabilities in rodents and in models of amnesia. We address the central mechanisms involved in mediating the modulation of learning and memory processes by neurosteroids. In this regard, the neurosteroid-modulated neurotransmitter systems, such as gamma-aminobutyric acid type A, N-methyl-D-aspartate, and cholinergic and sigma opioid systems, appear to be potential targets for the rapid memory alteration actions of neurosteroids. Moreover, given that some neurosteroids affect neuronal plasticity, this neuronal change could be involved in the long-term modulation of learning and memory processes. To understand the role of endogeneous neurosteroids in learning and memory processes, we present some physiological studies in rodents and humans. However, the latter do not successfully prove a role of endogenous neurosteroids in age-related memory impairments. Finally, we discuss the relative implication of a given neurosteroid vs its metabolites. For this question, a new approach using the quantitative determination of traces of neurosteroids by mass spectrometry seems to have potential for examining the role of each neurosteroid in discrete brain areas in learning and memory alterations, as observed during aging.
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ABSTRACT: It is widely believed that women who live together or who are close friends synchronize their menstrual cycles. We reexamined this phenomenon in two ways. First, we collected data on menstrual cycles from 186 Chinese women living in dorms for over a year. We found that women living in groups did not synchronize their cycles. Second, we reviewed the first study reporting menstrual synchrony. We found that group synchrony in that study was at the level of chance. We then show that cycle variability produces convergences and subsequent divergences of cycle onsets and may explain perceptions of synchrony.Human Nature 11/2006; 17(4):434-447. · 1.96 Impact Factor
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ABSTRACT: Japanese macaques reside in large, mixed-sex social groups in which various reproductive strategies of both sexes operate simultaneously. This report represents the first study combining behavioural and genetic data to examine the interaction of male and female reproductive strategies in primates (N=15 adult males, N=15 adult females, Yakushima Island, Japan). During one mating season, socially dominant males monopolized most female matings. Furthermore, the six offspring sired by troop males were more likely sired by higher-ranking males than lower-ranking males. Nontroop males sired three additional offspring in the troop. Lower-ranking troop males avoided direct competition with higher-ranking males by engaging in sneak copulations with females outside of the presence of other males. Also, females expressed mate choice behaviour towards multiple males of various dominance ranks. Thus, the female strategy of attempting to mate with multiple males conflicted with the mate-guarding strategy of high-ranking males. Despite some female mate choice for mid- and low-ranking males and alternative male mating tactics by subordinate males, high-ranking males were able to monopolize most, but not all, within-troop mating and paternity. This result was due in part to the low number of females mating at the same time. The mean number of females displaying mating behaviour per day was 2.42 (range 1–5), and higher-ranking males more successfully monopolized females on days when fewer females were mating. The number of females mating simultaneously influences the outcome of reproductive conflicts between the sexes.Animal Behaviour. 01/2001;
- TRE. 01/2000; 5(5):135-140.