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At least 127 records · Page 7Linked to original sources

Abnormal neurotransmitter release underlying behavioral and cognitive disorders: toward concepts of dynamic and function-specific dysregulation.

Abnormalities in the regulation of neurotransmitter release and/or abnormal levels of extracellular neurotransmitter concentrations have remained core components of hypotheses on the neuronal foundations of behavioral and cognitive disorders and the symptoms of neuropsychiatric and neurodegenerative disorders. Furthermore, therapeutic drugs for the treatment of these disorders have been developed and categorized largely on the basis of their effects on neurotransmitter release and resulting receptor stimulation. This perspective stresses the theoretical and practical implications of hypotheses that address the dynamic nature of neurotransmitter dysregulation, including the multiple feedback mechanisms regulating synaptic processes, phasic and tonic components of neurotransmission, compartmentalized release, differentiation between dysregulation of basal vs activated release, and abnormal release from neuronal systems recruited by behavioral and cognitive activity. Several examples illustrate that the nature of the neurotransmitter dysregulation in animal models, including the direction of drug effects on neurotransmitter release, depends fundamentally on the state of activity of the neurotransmitter system of interest and on the behavioral and cognitive functions recruiting these systems. Evidence from evolving techniques for the measurement of neurotransmitter release at high spatial and temporal resolution is likely to advance hypotheses describing the pivotal role of neurotransmitter dysfunction in the development of essential symptoms of major neuropsychiatric disorders, and also to refine neuropharmacological mechanisms to serve as targets for new treatment approaches. The significance and usefulness of hypotheses concerning the abnormal regulation of the release of extracellular concentrations of primary messengers depend on the effective integration of emerging concepts describing the dynamic, compartmentalized, and activity-dependent characteristics of dysregulated neurotransmitter systems.

Animals↗

[Influence of experimental epileptogenesis on memory: the role of lipids in cognitive disorders].

Learning and memory disorders accompanying epileptogenesis were studied in rats with the use of two experimental models of epilepsy, picrotoxin kindling and kainic treatment. Rise of exploratory activity and decrease in animal's capability for experimental extinction of a response were characteristic of the initial stage of epileptogenesis. It was suggested that a dysfunction of brain hippocampal system can be responsible for cognitive disorders. To reveal their mechanisms, lipid contents were determined in the neocortex and hippocampus in appropriate periods after exposure to epileptogenic factors. Long-term changes in hippocampal lipid spectrum were found five days after the exposure to kainic acid. In particular, after sodium valproate treatment (the compensation of kainic effects), the total content of phospholipids in hippocampus was decreased. The hippocampal sphingomyelin level dropped as a result of picrotoxin kindling. The sphingomyelin changes suggest some recovery processes in hippocampal cells and point to an adaptive role of membrane lipids in the mechanisms of the damaging epiptogenous effects.

Animals↗

[Detection of cognitive disorders in clinical practice].

The detection rate of cognitive impairment by general practitioners in elderly hospitalised and ambulatory population is low, ranging from 50 to 73%, and from 24 to 42%, respectively. This is insufficient regarding the importance of an early diagnosis of dementia and Alzheimer's disease, for the patient and his/her proxies, but also for the primary care physician in charge. Thus, all general practitioners should have a strategy for the evaluation of cognitive impairment in elderly patient.

Aged↗

[Magnetoencephalography in cognitive disorders involving frontal lobes].

INTRODUCTION AND DEVELOPMENT: Frontal lobe, more specifically prefrontal cortex, is one of the brain regions that undergoes more protracted ongoing development. The wider the developmental window of one brain structure, the more vulnerable the functions related to it. Hence, executive functions, which are mediated by prefrontal networks, seems to be specially vulnerable during childhood. Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent neurodevelopmental disorders. Functional neuroimaging techniques have shown a dysfunction in a fronto-striatal network in this disorder, that is likely subserving deficits in executive processes, such as in response inhibition. DISCUSSION: This review focuses on contributions of neuroimaging techniques, with high spatial (SPECT, PET and fMRI), temporal (ERP) and spatio-temporal (MEG) resolution, to the neurofunctionality of ADHD.

Attention Deficit Disorder with Hyperactivity↗

Moral judgment in relation to behavioral and cognitive disorders in adolescents.

The capacity for formulating moral judgments shown by 20 emotionally disturbed, cognitively delayed adolescents was related to their social behaviors as observed in a classroom situation. Adolescents reported by their teachers to be shy and submissive were less capable of reasoning about moral issues than were adolescents who were seen as more assertive and socially engaged. The level of moral judgment was not a function of intelligence or ability to understand concrete operations. The implication that social engagement is a critical determinant of moral judgment for these adolescents is discussed.

Adolescent↗

Executive dysfunction in attention-deficit/hyperactivity disorder: cognitive and neuroimaging findings.

Attention-deficit/hyperactivity disorder has been associated with a prominent disturbance of executive functions. There is no pathognomic neuropsychological profile for the disorder, however. Nonetheless, results of neuropsychological testing, in concert with other clinical information,provide a more comprehensive and detailed picture of the individual patient's cognitive and emotional strengths and weaknesses than a psychiatric diagnostic interview alone. This approach to the evaluation of ADHD therefore can provide a strong objective basis from which to make patient-specific recommendations for compensatory strategies and treatment. It should be noted, however, that although executive dysfunction in the form of impaired response inhibition remains the most prominent cognitive theory of ADHD, other theories have been put forth that also deserve further investigation. These include a disturbance in delay aversion (referring to intolerance for waiting) and impaired temporal processing, among others [79]. The neural substrates of executive dysfunction in ADHD have begun to be revealed by a growing body of structural and functional neuroimaging research. Although still in its infancy, neuroimaging of ADHD is pointing toward disruption of FSTC circuitry and the cerebellum as being central to the cognitive and motor abnormalities seen in the disorder. Further research using cognitive tasks assessing executive functions in combination with functional imaging techniques will provide further insight into the etiology of the disorder. It is expected that advances in structural and functional neuroimaging will yield valuable information that will facilitate the differential diagnosis of ADHD. Evidence cited suggests that psychostimulant medication can improve executive functions and their underlying FSTC circuitry. Furthermore, a recent study of adults with ADHD found significant improvements in organization skills and other symptoms of ADHD following cognitive remediation targeting several executive and emotional aspects of the disorder [80]. Additional studies investigating the effects of treatment on executive dysfunction and brain integrity in ADHD will be necessary to determine the degree to which the structural and functional brain abnormalities observed are mutable. Finally, because the myriad cognitive, behavioral and emotional symptoms in ADHD likely reflect the interplay of multiple cognitive and psychosocial factors, development of treatments for ADHD likely will require a multi-modal approach.

Attention Deficit Disorder with Hyperactivity↗

The cycle of schizoaffective disorder, cognitive ability, alcoholism, and suicidality.

In this study we investigated the putative role of cognitive dysfunction, diagnosis (schizoaffective versus schizophrenia disorder), and alcoholism as risk factors for suicidal behavior among individuals with DSM-TV schizophrenia or schizoaffective disorders. Subjects received cognitive tests and medical records were reviewed for evidence of a history of suicide attempts or suicidal ideation. Discriminant analysis was used to identify cognitive test performance measures that distinguished those with versus those without suicidal behavior. None of the cognitive measures discriminated between the two groups. The rates of suicidal behavior (suicidal ideation and suicide attempts) did not differ between participants with versus those without comorbid alcohol use. An association was found between suicidal behavior and the diagnosis of schizoaffective disorder. It was concluded that the history of prominent mood syndromes characteristic of schizoaffective disorder contributes to increased risk of suicidal behaviors. Cognitive dysfunction and/or alcoholism did not contribute additionally to risk in this study.

Adult↗

Diffusion tensor magnetic resonance imaging tractography in cognitive disorders.

PURPOSE OF REVIEW: The advent of novel techniques for tracing connections in vivo, such as diffusion tensor magnetic resonance imaging tractography, allows us, for the first time in the human brain, to study the microstructural integrity of white matter fibres and perform virtual dissections of large scale neurocognitive networks. This review will outline the advantages and limitations of applying diffusion tensor magnetic resonance imaging to the study of cognitive and behavioural disorders in neurology and psychiatry. RECENT FINDINGS: Diffusion tensor magnetic resonance imaging has been used to re-explore the anatomy of white matter tracts in the living human brain and to create connectional models of brain function. Beyond its application to classical disconnection syndromes, diffusion tensor magnetic resonance imaging is becoming an important tool to extend the disconnectionist paradigm to neurodevelopmental and neurodegenerative disorders. SUMMARY: For the first time, we are able to correlate disconnecting lesions with clinical symptoms in vivo and test the disconnection mechanism directly in cognitive disorders. With diffusion tensor magnetic resonance imaging tractography alone and in combination with other magnetic resonance imaging techniques, researchers are able to detect abnormalities in white matter that are not visible with conventional magnetic resonance imaging.

Anisotropy↗