Archives of gerontology and geriatrics. Supplement最新文献

Evidence for different types of memory in mice may lead to development of animal models for human memory disorders and provides informations on neurobiological systems underlying these processes. Series of experiments in mice, using a 8-arm radial maze with or without cholinergic drugs or chronic alcohol consumption supply arguments for multiple memory stores and for cholinergic influence greatest for short-term system. Studies of differential cholinergic activation following training militate for dissociation in time of hippocampal and cortical cholinergic pathways. Age-related memory involvement seems to be associated with an attenuation of central cholinergic activation. Several problems inherent to sensitivity and selectivity of the tasks remain in discussion.

The effect of age (20-86) and/or cultural level is investigated from the point of view of Cognitive Psychology. The study was carried out with 75 subjects distributed into 5 age-ranges and 3 cultural levels. It involved the following memory tests: forced choice recognition of faces (Warrington, 1984) and of abstract paintings; Rey Figure; immediate free recall; final free recall; learning and retention of paired associates; learning with AB-AC-AB design to test for interference; Selective Reminding test of Buschke (1973); repeated free recall. Data where analysed, taking into account dozens of variables. As far as age is concerned, all the analyses converge toward the same conclusion: short-term memory is not significantly affected by age, while a clear distinction appears between two kinds of secondary memory. Secondary memory involved in the course of learning or in the retention of learning is unaffected by age. By contrast, secondary memory involved in the retention of an initial or single confrontation with test material is very much affected by age. Age might, therefore, differentially affect two kinds of secondary memory. It is suggested that, contrary to the view of certain authors, age mainly affects automatic secondary memory, whereas voluntary, conscious, controlled and effortful secondary memory, which could require a greater amount of 'mental energy' or attentional resource, is relatively well preserved with age.

Memory loss is a common feature of aging in the human but not all memories are equally lost. Usually the loss is more severe for the memory of recent events and information rather than the memory of remote events and information. Associated with memory losses of this type is a reduction in levels of cortical acetylcholine and a loss of cholinergic cells of the nucleus basalis magnocellularis. In the rat it is possible to assess two types of memory analogous to recent and remote memories in humans. Reference memory would refer to information concerning the task that is invariant from trial to trial. Working memory would refer to information that changes from trial to trial. In support of the hypothesis that decreases in cholinergic function lead to a differential impairment of working memory, rats trained in this task and given scopolamine showed a specific increase in working memory errors. In more recent studies rats have been trained in a task and then given unilateral neurotoxic lesions of the NBM. These results raise the intriguing possibility that degeneration of the NBM and associated memory impairment seen in aging and in Alzheimer's disease may be related to a change in the ratio of these or related endogenous tryptophan metabolites.

Positron Emission Tomography has been used to compare patients with Alzheimer's disease and 3 patients with biopsy-proved Pick's disease to age-matched volunteers. In Alzheimer's disease, there was a trend to a decrease of the metabolism parallel to the severity of the affection. The hypometabolism was predominant in the temporo-parieto-occipital and the middle temporal regions. In 2 cases of Pick's disease with a classical "frontal syndrome", there was an important fronto-temporal hypometabolism, very suggestive of the diagnosis owing to both its location and intensity. A third patient presented with a slowly progressive dysphasia. A left perisylvian hypometabolism was observed before any evident anatomical abnormality. The clinical symptoms evolved to a dementia and the hypometabolism extended to both frontal lobes.

Memory performances are not constant but undergo fluctuations whose periodicity may be analyzed. Low frequency infradian rhythms (periods longer than 28 hours), circadian rhythms (periods between 20 and 28 hours) and ultradian rhythms (periods less than 20 hours) are involved in memory disorders. Paradoxical sleep represents a preferential period in which certain processes, such as the activation of the central nervous system for example, may facilitate learning process. Relations between sleep and memory lead to the discussion of the incidence of the cyclic nature of sleep (and notably the rhythm of 90 minutes' paradoxical sleep) on the daily course of cerebral activation and its effects on the variable aptitude of our capacity for remembering. The close interrelation between biological rhythms and cognition is demonstrated using two examples of mental disorders in which severe memory deficiencies are observed.