In this issue…
Memory is a fundamental mechanism of life. At the most elementary level, it is present in the molecules and cells that constitute us. As a psychological function, memory enables us to maintain a sense of identity, to conceptualize a temporal continuity between our past and our present, and therefore to anticipate our future and to pursue existential goals. Memory, both normal and abnormal, has long been studied in textbooks of psychology and psychiatry, from the viewpoints of phenomenology and psychological tests. Today, memory studies apply more sophisticated techniques, derived from molecular and cellular biology, genetics, and more recently, functional neuroimaging.
In the Guest Editorial for this issue of Dialogues in Clinical Neuroscience devoted to memory, Daniel L. Schacter (p 393) considers some of the prospects for applying memory research to a range of problems, from everyday life (eg, educational settings and the effectiveness with which students study for exams) to clinical conditions (eg, depressed patients).
Ruben C. Gur and Raquel E. Gur have contributed the State of the Art article (p 399), “Memory in health and in schizophrenia,” which outlines the history of work on memory and its neural underpinnings, and describes the major dimensions of memory processing that have been evaluated by cognitive neuroscience, focusing on episodic memory. Differences are associated with gender (females outperform males in verbal and face memory), age, and mental illness (impairment in schizophrenia is particularly noticeable in patients with negative symptoms). Memory deficits in schizophrenia are associated with abnormalities in frontal and medial temporal regions.
This issue contains three Translational research articles. These papers address the executive functions of working memory, the biological and cellular aspects of cognitive deficit in psychiatric disorders, and addiction disorders. In “The ‘working’ of working memory,” E. Miller (p 411) describes the importance of memory. What we think of as “thought” is a mental process that keeps information “in mind” in order to process it, and dynamically links the cortex-wide networks needed to complete the task. Prof Miller explains the synchronization of neural rhythms and its consequences on the mental mechanisms of human beings. The article “A neurobiological approach to the cognitive deficits of psychiatric disorders” by A. Etkin et al (p 419) shows how cognitive functions are affected in many psychiatric disorders, and considers the deficits in the brain networks that support regulatory cognitive functions. In the third Translational research article, E. Nestler (p 431) discusses “The cellular basis of memory for addiction.” Despite the enormous influence of psychosocial factors, addictive disorders also involve important biological processes. The author mentions the types of molecular and cellular adaptations that occur in specific brain regions that mediate addiction associated with behavioral abnormalities, including alterations in gene expression. The author also describes the role of epigenetics, the plasticity in the neurophysiologic functioning of neurons, and also the role of neurotrophic factors. He explains the types of drug-induced modifications that can be viewed as a form of “cellular or molecular memory,” showing us the addiction associated with molecular and cellular adaptations with repercussions in the same brain regions that participate in the mechanism of memory. Such studies attempting to explain the molecular and cellular basis of drug addiction can help in the development of treatments for the addictive disorders.
This issue continues with four Clinical research articles. These articles describe aspects of memory changes in Alzheimer’s disease (AD), other dementias, and various psychiatric diseases. The article “Memory loss in Alzheimer’s disease” by H. Jahn (p 445) details the role of molecular factors and neural networks in memory loss in AD, helping us to understand the role played by neural structures such as the default network, the role of genetic factors such as ApoE4, and the epigenetic factors. The author also explains the development of possible biological markers in Alzheimer’s disease. Continuing the topic of memory loss, C. Pittenger writes about “Disorders of memory and plasticity in psychiatric disease” (p 455). He shows how changes in neuroplastic and neurogenesis processes of cellular growth related to the development of learning and memory can contribute to different neuropsychiatric diseases. The author explores the role played by stress, major depression, and post-traumatic stress in decreased or increased memory. He also mentions how the disturbance of memory has an important role in OCD, addiction, etc. The other articles in this issue also show that the understanding of such mechanisms may lead to development of new and more effective treatments. The aim of the article “Non-Alzheimer’s disease–related memory impairment and dementia” by S. Arlt (p 465) is to explain the importance of the distinction between AD and Non-AD in memory impairment in order to establish new therapeutic strategies. The author describes the new studies that contribute to a better understanding of a differential diagnosis between AD and non-AD related memory impairment in the presence of memory deficits. “Memory as a new therapeutic target” is the topic developed by K. Nader, O. Hardt, and R. Lanius (p 475). The authors show how the elucidation of the mechanisms involved in memory processing can help us to revise our understanding of mental disorders as well as the treatments. They describe how the neurosciences have contributed to the revision of the understanding of mental disorders we have today.
The Brief report by P. Fossati (p 487), “Imaging autobiographical memory,” explores the neural correlations of autobiographical memory, ie, the memory systems that encode, consolidate, and retrieve personal events and facts. The studies of memory using brain imaging have demonstrated the role played by the brain regions involved in this process, with a special emphasis on the structures of prefrontal cortex, temporal lobes, and parietal regions as well as the limbic structures. The author reviews several brain imaging studies using PET or functional MRI to investigate the neural correlates of AM retrieval.
In conclusion, this issue contributes to a better understanding of the role of memory in mental and behavioral functions, as well as in various neurological and psychiatric diseases. This might lead to a revision of diagnostic criteria and therapeutic methods in these diseases. This issue also shows that not only the understanding of the psychological and clinical features, but also the knowledge of cellular, molecular, genetic, and epigenetic characteristics of brain networks involved in memory processes can help us arrive at a better understanding and diagnosis of diseases, and also assist in the development of new educational techniques.
Jorge Alberto Costa e Silva, Marc-Antoine Crocq