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Electrophysiological aberrations associated with negative symptoms in schizophrenia
No full textClinical heterogeneity is a confound common to all of schizophrenia research. Deficit schizophrenia has been proposed as a homogeneous disease entity within the schizophrenia syndrome. The use of the Schedule for the Deficit Syndrome (SDS) has allowed the definition of a subgroup dominated by persistent and primary negative symptoms. While a number of studies have appeared over the years examining the electrophysiological correlates of the cluster of negative symptoms in schizophrenia, only a few studies have actually focused on the Deficit Syndrome (DS). In this chapter, electrophysiological investigations utilizing EEG, Evoked Potentials (EPs), polysomnography (PSG), or magnetoencephalography (MEG) to probe ‘‘negative symptoms,’’ or ‘‘Deficit Syndrome’’ are reviewed. While this line of research is evidently in its infancy, two significant trends emerge. First, spectral EEG studies link increased slow wave activity during wakefulness to the prevalence of negative symptoms. Second, sleep studies point to an association between decrease in slow wave sleep and prevalence of negative symptoms. Several studies also indicate a relationship of negative symptoms with reduced alpha activity. A host of other abnormalities including sensory gating and P300 attenuation are less consistently reported. Three studies specifically addressed electrophysiology of the DS. Two of the three studies provided evidence suggesting that the DS may be a separate disease entity and not simply a severe form of schizophrenia
Physiological correlates of positive symptoms in schizophrenia
No full textPatients with schizophrenia have been hypothesized to have a functional impairment in filtering irrelevant sensory information, which may result in positive symptoms such as hallucinations or delusions. Many evidences suggest that abnormalities in the event-related brain potentials (ERPs), resting state electroencephalography (EEG) and synchronized oscillatory activity of neurons may reflect core pathophysiological mechanisms of schizophrenia. Abnormalities in amplitude and latency of the ERPs reflecting aberrations in gating and difficulties in the detection of changes in auditory stimuli, as well as defects in stimuli evaluation and integration of information are common in patients with schizophrenia. This chapter highlights the findings of electrophysiological studies in schizophrenia dealing with early sensory perception and attention, automatic sensory detection of stimuli changes and cognitive evaluation and integration of information, relevant to the pathophysiological mechanisms underpinning hallucinations and delusions. Results of electrophysiological studies investigating the neural correlates of positive symptoms suggest aberrant intrinsic organization of functional brain network
Negative symptoms in schizophrenia: A comprehensive review of electrophysiological investigation
No full textClinical heterogeneity is a confound common to all of schizophrenia research. Deficit schizophrenia has been proposed as a homogeneous disease entity within the schizophrenia syndrome. Utilizing the Schedule for the Deficit Syndrome (SDS) has allowed the definition of a subgroup dominated by persistent clusters of negative symptoms. While a number of studies have appeared over the years examining the electrophysiological correlates of the cluster of negative symptoms in schizophrenia, only a few studies have actually focused on the deficit syndrome (DS). PubMed as well as MEDLINE were searched for all reports indexed for "negative symptoms" or "deficit syndrome" and one of the following electrophysiology assessment tools: electroencephalography (EEG), evoked potentials (EPs), or polysomnography (PSG). While this line of research is evidently in its infancy, two significant trends emerge. First, spectral EEG studies link increased slow wave activity during wakefulness to the prevalence of negative symptoms. Secondly, sleep studies point to an association between decrease in slow wave sleep and prevalence of negative symptoms. Several studies also indicate a relationship of negative symptoms with reduced alpha activity. A host of other abnormalities - including sensory gating and P300 attenuation - are less consistently reported. Two studies specifically addressed electrophysiology of the DS. Both studies provided evidence suggesting that the DS may be a separate disease entity and not simply a severe form of schizophrenia
Preface
No full textThis book provides a concise overview of the possible clinical applications of standard EEG in clinical psychiatry. After a short history, the book describes the physiologic basis of the EEG signal, then reviews the principles of EEG in terms of technical backgrounds and requirements, EEG recording and signal analysis, with plentiful illustrations of the most frequent biological or technical artefacts. Normal EEG patterns and waveforms for easy reference are clearly presented, before the detailed description of abnormal patterns. With the basic information in hand, the reader progresses to an account of the role of EEG in the diagnostic work up in psychiatry, covering nonconvulsive status epilepticus, frontal lobe seizures and non-epileptic seizures. The clinical application of EEG in both childhood and adult disorders follows, including many case vignettes. The effects of psychotropic drugs on EEG are highlighted. The book closes with a discussion of currently available certification venues for Clinical Neurophysiology along with limitations of each venue. It calls for the development of training guidelines and certification processes specific to Psychiatric Electrophysiology. The material is clearly presented throughout, with plenty of figures, tables with summaries of relevant findings, flow diagrams for diagnostic work-up, boxes with learning points, and short lists of key references. We fully expect the book will become the standard teaching source for psychiatry residents and fellows, as well as a useful resource for practising psychiatrists and clinical psychologists. Praise for the book: "This distinguished group of editors has put together chapters that represent an excellent practical handbook on electroencephalography in clinical psychiatry, now a very important topic. I highly recommend it not only to psychiatrists, but also to anyone interested in neuroscience." John R. Hughes, DM (Oxon), MD, PhD, Professor of Neurology, University of Illinois Medical Center, at Chicago, Illinois, USA
The status of spectral EEG abnormality as a diagnostic test for schizophrenia
No full textObjective: A literature review was conducted to ascertain whether or not EEG spectral abnormalities are consistent enough to warrant additional effort towards developing them into a clinical diagnostic test for schizophrenia. Methods: Fifty three papers met criteria for inclusion into the review and 15 were included in a meta-analysis of the degree of significance of EEG deviations as compared to healthy controls. Studies were classified based on a 4-step approach based on guidelines for evaluating the clinical usefulness of a diagnostic test. Results: Our review and meta-analysis revealed that most of the abnormalities are replicated in the expected directions with the most consistent results related to the increased preponderance of slow rhythms in schizophrenia patients. This effect remained consistent in un-medicated patients. Only a small number of studies provided data on the sensitivity and specificity of the findings in differentiating among the psychiatric disorders that frequently appear on the same differential diagnostic list as schizophrenia (Step 3 studies). No multicenter studies using standardized assessment criteria were found (Step 4 studies). Conclusions: Additional Step 3 and Step 4 studies are needed to draw conclusions on the usefulness of EEG spectral abnormalities as a diagnostic test for schizophrenia
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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