睡眠的记忆巩固功能研究进展

睡眠和学习记忆同属于大脑最重要的基本功能．大量的动物实验和人体研究都证明睡眠在记忆巩固中发挥重要作用．综合此领域近年来的研究成果,着重阐述睡眠期间海马和皮层的记忆巩固过程,并简要介绍所涉及的初步的细胞和分子机制．     

睡眠剥夺对记忆功能及突触可塑性的影响

睡眠剥夺（SD）不仅会直接影响工作效率,还会随着疲劳程度的增加,对个体的记忆、注意力和学习等多种认知功能造成负面影响。在过去的几十年里,研究人员围绕SD对各种认知功能,尤其是对记忆功能的影响,开展了大量的研究。本文首先基于行为学研究综述了SD对记忆功能的影响,并进一步从结构和功能突触可塑性、兴奋性和抑制性神经递质水平以及相关突触蛋白信号表达等方面阐述了SD生理机制研究的最新进展。发现SD通过影响突触的活动变化（如树突棘密度、突触之间的连接和突触的兴奋和抑制的平衡）,从而对相关突触蛋白信号表达和下游信号通路进行调节,最终表现在行为学水平上。本文对SD影响记忆功能及其机制的研究进展进行综述,为今后进一步研究睡眠功能和相关机制,以及发展相关方法来改善SD引起的记忆功能缺陷提供参考。     

Phenotypic variation in colour pattern and seasonal plasticity in Eristalis hoverflies (Diptera: Syrphidae)

Abstract.

• 1 An examination of phenotypic variation in colour pattern was carried out on four Eristalis hoverfly species using museum material.
• 2 The amount of phenotypic variation varied substantially among the species with E.arbustorum being the most variable. The other species showed a wide colour pattern range but less variation within that range (E.abusivus and E.nemorum), or a narrow range of colour variation (E.horticola).
• 3 Sexual colour dimorphism was apparent in all four species, but most pronounced in E.abusivus and E.nemorum.
• 4 There were good phenotype-season relationships shown by both sexes in all species, except for female E.abusivus and E.nemorum, with paler insects being more abundant during the warmer summer months.
• 5 Female, but not male, E.arbustorum collected at inland sites were on average paler than those collected at coastal sites. This observation is considered with respect to temperature during the developmental stages.
• 6 The function of colour plasticity in hoverflies is discussed with reference to the need to maintain optimal thermal conditions for activity.

     

Experience-induced changes in taste identification of monosodium glutamate (MSG) are reversible

A few studies have reported experience-inducible changes in human taste and olfactory sensitivities. However, no study thus far has systematically characterized the stability of the enhanced sensitivities. In our previous study, we found increases in taste identification ability for monosodium glutamate (MSG) in subjects who had been briefly exposed to MSG in food for 10 days. Here, we tested the temporal stability of the enhanced taste identification ability. First, we exposed a group of 20 subjects to MSG in food and then compared their sensitivities to MSG with those of a control group. When tested on day 11 or 12, the mean MSG taste identification ability of the MSG-exposed group was significantly higher than the control group. Next, 11 of the subjects who were exposed to MSG in food initially, and then stopped being exposed performed significantly poorer in identifying MSG after 10 days of the nonexposure than they did 10 days before. In contrast, nine subjects who were exposed to MSG initially and continued being exposed maintained their high identification levels. These results support earlier finding of the plasticity in the taste identification of MSG and show that the enhanced identification ability can be reversed rapidly when MSG exposure is not sustained.     

Stage-related variation in rapid cold hardening as a test of the environmental predictability hypothesis

The environmental predictability (EP) hypothesis proposes that rapid cold hardening (RCH) might be common in temperate species incapable of surviving freezing events and which also dwell in unpredictable environments. The kelp fly Paractora dreuxi serves as a useful model organism to test this prediction at an intra-specific level because larvae and adults show different responses to low temperature despite occupying a similar unpredictable thermal environment. Here, using acclimation temperatures, which simulated seasonal temperature variation, we find little evidence for RCH in the freeze-intolerant adults but a limited RCH response in freeze-tolerant larvae. In the relatively short-lived adults, survival of -11 degrees C generally did not improve after 2h pre-treatments at -4, -2, 0, 10, 20 or 25 degrees C either in summer- (10 degrees C) or winter (0 degrees C)-acclimated individuals. By contrast, survival of summer-acclimated larvae to -7.6 degrees C was significantly improved by approximately 37% and 30% with -2 and 0 degrees C pre-treatments, respectively. The finding that summer-acclimated larvae showed RCH whereas this was not the case in the winter-acclimated larvae partially supports the predictions of the EP hypothesis. However, the EP hypothesis also predicts that the adults should have demonstrated an RCH response, yet they did not do so. Rather, it seems likely that they avoid stressful environments by behavioural thermoregulation. Differences in responses among the adults and larvae are therefore to some extent predictable from differences in their feeding requirements and behaviour. These results show that further studies of RCH should take into account the way in which differences among life stages influence the interaction between phenotypic plasticity and environmental variability and predictability.