Nature and amplitude of the effects of acetoxycycloheximide on the retention of an instrumental task in mice (author's transl)

Mice injected subcutaneously with AXM (7 mg/kg) 60 minutes or less after acquisition of a nondiscriminative instrumental task, show low levels of lever press responding, when tested 6 days after the treatment. AXM injected 180 min after acquisition has no effect whatsoever on the performance. The analysis of various parameters such as, (1) the number of nonreinforced responses (A) preceding the first reinforced response (AR), and (2) the latency of the first reinforced response, shows that only the animals treated with AXM during the first 3 min following acquisition differ significantly from the control animals: they seem to have forgotten the significance of the lever. On the contrary, the low levels of responding observed in the animals treated 30–60 min after acquisition does not seem to be due to a nonretention of the significance of the liver. The mechanisms by which the AXM affects the level of responding remain obscure.     

Métamémoire, remémoration et familiarité dans la maladie d’Alzheimer

Introduction

The main objective of this review is to present a new approach to the memory deficit in Alzheimer's disease. Recent memory models suggest that information is recovered either on the basis of recollection or on the basis on familiarity. Recollection, unlike familiarity, requires the retrieval of contextual details related to the encoded information.

State of the art

This review suggests that recollection is particularly affected in Alzheimer's disease. In contrast, familiarity seems to be relatively preserved. A related deficit in metamemory is observed when recollection is required; a decrease in recollection in Alzheimer's disease could explain the pattern of metamemory problems. The deficit in recollection could be explained by a disconnection between medial temporal areas and frontal areas.

Perspectives

This novel approach to memory gives research perspectives concerning both early diagnosis and rehabilitation strategies of Alzheimer disease.

Conclusion

This overview showed deficits in conscious memory processes conceived of as recollection. These novel insights should provide new explanations for the deficits observed in Alzheimer's disease, particularly metamemory.     

Neuropsychological markers for the diagnosis of Alzheimer's disease

Better knowledge of the preclinical phase of Alzheimer's disease and of the symptomatic pre-dementia stage designated "mild cognitive impairment" will require considerable progress in our understanding of neuropsychological processes. The results of studies suggest that impaired performance in memory tests may serve as a marker for Alzheimer's disease. The best current predictors include stringent tests of episodic memory and recognition tests. The early stages of Alzheimer's disease also seem to involve subtle deficits in semantic memory and attentional processes. Face recognition and denomination seem to be useful tools. Greater accuracy and precision in the transitional zone between healthy aging and the first manifestations of Alzheimer's disease will require work combining data on neuropsychological profiles and neuroimaging.     

Assessment of neuropsychological impairments in regular cannabis users

BackgroundCannabis is the most widely used illicit drug in the world. It is responsible for cognitive dysfunction of memory, speed of information processing, attention, and executive functions. Cognitive performance depends on the level of study, tolerance, and duration of abstinence from cannabis use. This study analyses cognitive function in a large population of regular cannabis consumers taking into account level of education.MethodsA battery of neuropsychological tests using the Cambridge Neuropsychological Test Automated Battery was performed on a population of 58 cannabis users categorized into two groups according to their level of education with a threshold of 12 years of study, and 25 non-users.ResultsIn Attention Switching Task percent correct trials, significant differences were found between the group of cannabis smokers with less than 12 years of study and the non-smoker group (P = 0.022), and between the cannabis users with more than 12 years of study and the non-smoker group (P = 0.008). A significantly lower performance in the Rapid Visual Information Processing (Mean latency, Probability of hit, Total hits, Total misses, Correct rejections) was found in the cannabis users with less than 12 years of study compared with the non-user group.ConclusionIn our population, chronic cannabis users presented divided and sustained attention and working memory disorders. Rapid Visual Information Processing performance may be influenced by education level in cannabis smokers.     

Connaissance des nouveaux mots de la langue française dans les troubles cognitifs légers de type amnésique et la maladie d’Alzheimer

Introduction

The first decline in cognitive performance in Alzheimer's disease can appear when assessing semantic memory and can be detected long before the typical symptoms of Alzheimer's disease (AD), appearing with Mild Cognitive Impairment (MCI).

Patients and method

We propose the French version of the New Words Interview (fNWI) using 22 words to investigate semantic knowledge. The fNWI uses 11 words, which entered the French dictionary between 1996 and 1997, and 11 other words, which entered between 2006 and 2007. Words were paired according to orthographic and semantic criteria. Each word was associated with three sub-tests: free evocation, discrimination of the best definition from three propositions, and recognition of the accurate word context (two sentences were proposed). Regarding evocation, we distinguished conceptual definition, life situation examples or examples by use. We tested 12 patients with AD, 12 patients with amnesic Mild Cognitive Impairment (aMCI) and 72 controls (12 were paired with patients for age and education level).

Results

MCI patients and AD patients exhibited lower performance than controls in the three sub-tests and for the words of both periods. From the early stage of MCI, the patients were more impaired in the fNWI than in the context recognition task, and they failed to provide conceptual definitions of new words. Therefore, MCI patients suffer from semantic impairments before obvious clinical signs of AD.

Conclusion

In patients with AD, performance worsened on all subtests, and more strongly in the definition discrimination task, which suggests the impairment of stored semantic knowledge. They provided fewer conceptual definitions and failed to use the strategy observed in MCI patients, who compensated for conceptual difficulties by providing examples.     

Étude des liens entre sommeil et mémoire épisodique chez le sujet jeune et âgé, et dans la maladie d’Alzheimer

Introduction

A large body of evidence indicates that sleep favors memory consolidation.

State of the art

This process would occur, mainly during slow-wave sleep, by means of a dialogue between the hippocampus and neocortical areas. Low levels of acetylcholine and cortisol are also needed to favor the transfer of memory traces toward the neocortex, where they will be stored for the long-term.

Perspectives

The aim of this article is, first, to give an overview of studies conducted in young healthy subjects and underpinning the hypothesis that sleep is involved in memory consolidation. Then, we will investigate the potential links between changes in sleep architecture and episodic memory impairment in both aging and Alzheimer's disease. Finally, we will see how these results can affect clinical practice.

Conclusion

Sleep-dependent memory consolidation is impaired both in aging and Alzheimer's disease. These findings suggest the importance of taking into account sleep when assessing memory function in patients.     

Memory: a view of the history of central nervous system

In order to stress the role and importance of memory in human nervous system, this first paper intends to show how it appeared during evolution with the cortex of brain hemispheres and how its significant growth is the cause (and not consequence) of hominization. This growth seems related to a discontinuation of the fetal period during gestation. It leads to birth before the brain is mature, substituting a genetic maturation by an epigenetic maturation through learning. This discontinuation of pregnancy is related to a purely mechanical and obstetrical cause, depending on maternal pelvis. Evolution from quadrupedia to bipedia transformed the pelvis, obliging the newborn to make his way not downward but forward, through a narrow inextensible pass. This history of memory, showing its role in human species evolution, may lead to a reflection on its role in the evolution of all the species possessing a cortex. Above all, it will allow to understand how and in which way human brain is a sort of machine totally associated with memory.