Fonctions cognitives sous-jacentes aux déficits de fluence verbale dans la schizophrénie : revue de la littérature

Individuals with schizophrenia usually show impairment on various cognitive functions, including long-term memory, executive functions and language. Compared to healthy controls, their performance is impaired in verbal fluency tests. These tests require participants to generate in a given time as many words as they can, belonging to a given category (semantic fluency), or beginning with a specific letter (orthographic fluency). Various cognitive functions are involved in verbal fluency tests: psychomotor speed, executive functions, language, long-term verbal memory and semantic memory. The purpose of the present study was to clarify the functional origin of verbal fluency deficits in schizophrenia through a literature review. Nineteen articles were selected in Pubmed and PsycINFO after initial screening and detailed review. They were formally analyzed with regard to general performance, cognitive strategies used in semantic and orthographic fluency tests and, underlying cognitive origin of deficits. Results show that individuals with schizophrenia produce fewer words than healthy controls in both types of fluency tests. Their impairment is more apparent in semantic than in orthographic fluency tests. Results of studies reviewed also show that individuals with schizophrenia adopt the same clustering (i.e. production of related words within a subcategory) and switching (i.e. ability to shift between clusters when a subcategory is exhausted) strategies than healthy controls, but less efficiently. Several hypotheses, such as the impairment of executive functions, semantic memory or speed of information processing, were put forward to account for this finding. Interestingly, the few studies in which researchers performed an analysis of the semantic relationships between words produced in fluency tests showed a less semantic coherence among people with schizophrenia than in healthy controls. Such a difference could be explained by disorganization of semantic memory or impairment in the activation of conceptual representations in semantic memory. Studies in which correlations and regression analyzes were performed allow for clarifying the cognitive origin underlying verbal fluency deficits in schizophrenia. The links between these deficits and information processing speed as well as working memory are well established. These two cognitive domains also appear to be strong predictors of performance in semantic and orthographic fluency tasks in schizophrenia. Individuals with schizophrenia usually present with a significant slowdown in the speed of information processing. Such a slowdown is likely to account for their poor performance in verbal fluency tests, which require the independent and rapid production of words. Working memory disorders are also core cognitive symptoms of schizophrenia. Working memory is involved in verbal fluency tests since they involve “strategic” activation of verbal information in long-term memory, inhibition of inappropriate words, switching between clusters, etc. However, the concept of working memory also partially encompasses the notion of executive functions so that the results reported in the present literature review, according to which impairment of verbal fluency in schizophrenia results from working memory deficits but not from executive functions deficits, are difficult to interpret. Results are also less clear-cut in regard to verbal long-term memory and to language abilities. Finally, numerous studies had shown that individuals with schizophrenia present specific deficits in the organization of semantic memory. However, the impact of this deficit on verbal fluency was explored in one study only. To conclude, verbal fluency tests are sensitive to various neurocognitive conditions and are helpful for differential diagnosis. Further studies are still needed to clarify the functional origin of verbal fluency deficits in schizophrenia, in particular the differential role of executive functions and working memory as well as the impact of semantic memory impairment.     

正常人面部的对称性研究

本研究以70名正常青年人为对象,用SCC—I型头部云纹摄影仪拍摄面部正位云纹片、面部侧位30°及45°云纹片,进行面部对称性研究。本研究中确定了NV为面部中线,FH为面部矢状断面对称性分析的参考线;提出了面部中线结构偏差(D)及面部对称结构偏离度(Dd)的概念及计算方法;建立了额状面、水平面及矢状面上面部对称分析的方法,面部水平断面平均偏高度、额状断面平均偏离及矢状断面平均偏离度均小于10％,中线结构偏差小于2mm。     

Effects of cycloheximide on acquisition and retention of an avoidance learning in the rat: recovery of memory (author's transl)

Thirty minutes before an avoidance learning session in a Y maze, rats were given a subcutaneous injection of either cycloheximide (2,5 mg/kg) or saline. The animals were trained to a criterion of 4 or 8 consecutive avoidance responses. Retention tests were given 2 hr, 24 hr or 6 days after initial learning. The results show: (1) acquisition is not affected by the severe protein synthesis inhibition; (2) impairment of memory is found only in the low criterion experimental group 2 hr after learning and (3) in both experimental groups 24 hr after learning; (4) a recovery of memory is observed in both groups 6 days later. A control experiment indicates that the deficits found cannot be regarded as retrieval deficits. Transient amnesia is interpreted in terms of slowing down in long-term memory establishment process and this is thought to be due to a decrease in the rate of neurotransmitter synthesis.     

Mémoire émotionnelle du soi

Emotion shapes autobiographical memory (AM) by tagging events that are relevant for the narrative self, which may be viewed as a hierarchical network of interconnected goals. Subsequent AM retrieval is a reconstruction process that grounds the self by providing coherent narratives organized to elicit a sense of identity across the time. The lateral and medial prefrontal cortices underlie reconstruction and self-referential processing, respectively, whereas the lateral and medial temporal cortices underlie semantic and episodic aspects, respectively. Additionally, the posterior cortical midline structures and the amygdala are involved in visual and emotional aspects, respectively. These regions have been found to display aberrant functioning in major depression. Accordingly, major depression is associated with impairments of AM retrieval combining mood-congruency, overgenerality, intrusive memories and third-person visual perspective.     

The 5-word test in 37 depressed patients compared with 36 normal controls and 35 patients with mild Alzheimer's disease

Objectives

Patients with major depression (MD) express frequent memory complaints leading to consultations in memory clinics. The 5-word test (5WT) is a verbal memory test with semantic cueing, which has shown its sensitivity and its specificity in identifying patients with Alzheimer's disease (AD). Our objective was to evaluate memory performances of aged patients with MD compared with controls and AD patients.

Methods

Characteristics of the 5WT were investigated in a sample of 37 patients with MD (66.8 ± 7.5 years) compared with 36 normal controls (67.3 ± 6.8 years) and 35 mild AD patients (67.5 ± 6.1 years).

Results

Duration of depression was 15.3 ± 11.5 years. Memory complaints of MD patients were ancient (4.6 ± 5.5 years) and severe (McNair memory questionnaire = 47.6 ± 20.7). The Total score of MD patients did not differ from controls but was greater than those of AD patients. Learning and Memory scores of MD patients were significantly lower than those of controls and significantly greater than those of AD patients. Forgetting rate between Learning and Memory scores was more important in AD (72.4%) than in controls (2.8%) and MD (13.6%). No intrusions were recorded in controls, three MD patients each made one intrusion, whereas 80% of AD patients made between one to six intrusions (mainly during cued delayed recall). Receiver operating characteristic curves determined the most significant cut-off scores of the Total score. It appeared easy to discriminate AD patients from controls (cut-off = 9, sensitivity = 94.3%, specificity = 100%) or MD patients (cut-off = 8, sensitivity = 88.5%, specificity = 89.2%) whereas it was more difficult to discriminate MD patients from controls (cut-off = 10, specificity = 88.9%, sensitivity = 37.8%).

Discussion

MD patients had significant difficulties with the 5WT as compared to controls, without being of the magnitude of those observed in AD patients.

Conclusion

The 5WT allows a reliable evaluation of memory in MD patients. The presence of true memory deficits with the 5WT could not be ascribed to depression but to other pathological conditions. Consequently, further memory testing should be conducted.     

Fonctionnement de la mémoire chez les sujets avec autisme

Introduction

Autism is an early developmental disorder with cognitive impairments that leads to learning and social integration disabilities. The characterization of memory functions in individuals with autism has been the subject of numerous investigations, with widely varying conclusions. The notable differences between these studies can be attributed to variations in the age, intelligence and level of severity of the participants with autism.

Literature findings

The purpose of our review of the recent literature is to describe the memory function of individuals with autism. Some of the different memory subtypes are intact, others are impaired. Short-term memory (digit span) is not impaired while working memory is impaired in some of its components, but the findings are inconsistent. More recent studies demonstrate reduced spatial working memory abilities in autism and extend previous findings by demonstrating that these deficits are significant when tasks impose heavier demands on working memory. Episodic long-term memory, as measured by free recall, cued recall or recognition tasks, is intact, but participants with autism perform significantly less well than controls as the complexity of the verbal or visual material to be recalled increases. Source or contextual memory involves a variety of characteristics specifying the conditions under which specific items or facts are acquired: it has been investigated in individuals with autism with different methods. Deficits in source memory for temporal information have been found, but there were no reality monitoring deficits. Recent findings indicate that the nature of source memory confusion in autism does not appear to reflect a generalized deficit in attaching context to memories, but rather is dependant on the specific to-be-remembered information that involves social aspects of context. The self-reference effect is missing, with individuals with autism recalling events performed by themselves less well than the events performed by a peer, suggesting they have difficulties in relation to processes involving the self. Studies involving assessment of subjective states of awareness during recognition show less conscious recollection and more feelings of familiarity. Recent investigations are consistent in demonstrating memory impairments related to the failure of subjects with autism to use organizing strategies or meaning to support memory, an effect which grows with the increasing complexity of the material. Memory deficits in autism may be related more to retrieval and less to encoding, as deficit in source memory in participants with autism is largely eliminated when source was supported at test.

Discussion

The neuroanatomical basis of the specificities of memory impairment in autism is still uncertain, but it is suggested that autism involves an impairment in the conversion of limbic inputs into medial prefrontal outputs. Memory deficits found in individuals with autism may explain some of the clinical symptoms. Failure to encode all the information, especially its social aspects, may therefore contribute to dysfunction in the social, communication, and reasoning domains. Abnormal memory functioning in autism is also related to more general cognitive impairments, including executive function deficits and central coherence weakness. Evidence of the normality of certain memory capacities, at least in individuals with moderate autistic symptomatology, is encouraging for adaptive improvements in cognitive functioning.     

Traitement de l’information à contenu émotionnel et représentation de soi chez des patients bipolaires de type I après traitement combiné médicamenteux et comportemental-cognitif

Objectives

Bipolar disorder currently affects around 1 % of the general population. Despite mood stabilizers, 37 % of patients continue to present mood fluctuations. Moreover, psychotherapeutic approaches, together with prophylactic treatment, have been developed over the past 10 years, including the behavioural and cognitive approach. Lam's behavioural model has thus become a major reference. Bipolar patients who have undergone cognitive behavioural therapy (CBT) based on this program experience fewer manic and depressive recurrences as well as fewer hospitalizations, thus improving the quality of their relations with others, reducing their dysfunctional beliefs and attitudes, and enhancing their self-esteem. However, no study has evaluated the effects of CBT on cognitive functions in this disorder, such as memory, nor on its connection with cognitive patterns, among bipolar patients. Previous research has suggested the existence of many disturbances of cognitive functions. Several studies have demonstrated memory disturbances in a free recall task among type I bipolar patients, even during periods of remission. However, none of these studies focused on explicit-memory recall bias for words with affective valence during remission, nor did they investigate the connection between self schemata and bias in memory processes. The goal of this study was to explore the cognitive vulnerability of bipolar I patients in remission by linking self schemata with recall bias for words with affective valence, and to compare these variables among patients who underwent CBT, and patients who did not.

Materials and methods

The study included 24 bipolar I patients, 12 were in the control group (mood regulating treatment) and 12 were in the experimental group (CBT in conjunction with a mood stabilizer), according to the DSM-IV criteria. The free recall tasks for words with distinct affective valences (positive, neutral, negative) allowed us to assess the performance and recall bias for affective information. In addition, the lexical assessment enabled us to study the cognitive schemata with reference to self-representation.

Results

The results do not indicate any signs of depression, mania or anxiety among the two groups at the time of their inclusion in the study. The cognitive results show that not only is the experimental group significantly more likely to recall words with positive affective valence (F1, 22 = 5.770; P = 0.025) and significantly less likely to recall those with negative affective valence (F1, 22 = 6.629; P = 0.017) than the control group, but that it also presents a specific recall bias for words with a positive connotation as compared to neutral words (t11 = 4.722; P = 0.001) and negative words (t11 = 5.777; P < 0.0001). Furthermore, the experimental group uses a vocabulary which is less focused on the disorder mood and cognitive symptoms.

Conclusion

The results demonstrate the various recall biases between the two groups, with a specific bias for the positive words and a self-representation which is less focused on bipolar illness in the experimental group. Learning the cognitive and behavioural coping strategies based on the Lam et al. model may lead to a modification of bipolar patients’ cognitive schemata. This modification may itself contribute to a better recall of positive stimuli. Just as, according to Bower, the activation of a negative emotion may facilitate the recall of negative information, a better management of emotions seems to result in a better recall of positive information.     

Critères diagnostiques des troubles cognitifs légers dans une cohorte de 100 patients

Introduction

Tracking can be proposed for subjects with prodromal sates of Alzheimer disease (AD) or people with mild cognitive impairment (MCI) at risk to develop dementia who present a memory complaint.

Patients and methods

We present a cohort of 100 subjects who attended a French memory unit with a diagnostic of MCI. We applied the different definitions used in daily practice. We used the following diagnostic criteria: amnestic MCI (MCIa), multiple domain impairment (MDI), single non-memory dysfunction impairment (SDI), and prodromal Alzheimer's disease (Prod-AD), using only the neuropsychological episodic memory criteria. We also analyzed the population of subjects presenting MCI and vascular risk factors.

Results

Ninety-nine subjects met the criteria of MCIa, 43 met the criteria of isolated MCIa; 56 met the criteria of MDI; one met the criteria of SDI; 40 met the criteria of MAPD; 58 met the criteria of MCI with vascular risk factors.

Discussion

Using the diagnostic criteria of MCI can lead to clinical ambiguity because the population recruited on the bases of memory complaint is highly variable. Moreover, many subjects meet many definitions. This overlap of the classifications further complicates the decision to favor one criterion over another. In clinical practice, a classification system using the concepts of MCI, MDI and SDI seems to be quite operational but cut-offs are necessary for the tests applied, in addition to a clarified choice of which tests to use.