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Krystal JH, Abi-Dargham A, Akbarian S, Arnsten AFT, Barch DM, Bearden CE, Braff DL, Brown ES, Bullmore ET, Carlezon WA, Carter CS, Cook EH, Daskalakis ZJ, DiLeone RJ, Duman RS, Grace AA, Hariri AR, Harrison PJ, Hiroi N, Kenny PJ, Kleinman JE, Krystal AD, Lewis DA, Lipska BK, Marder SR, Mason GF, Mathalon DH, McClung CA, McDougle CJ, McIntosh AM, McMahon FJ, Mirnics K, Monteggia LM, Narendran R, Nestler EJ, Neumeister A, O’Donovan MC, Öngür D, Pariante CM, Paulus MP, Pearlson G, Phillips ML, Pine DS, Pizzagalli DA, Pletnikov MV, Ragland JD, Rapoport JL, Ressler KJ, Russo SJ, Sanacora G, Sawa A, Schatzberg AF, Shaham Y, Shamay-Tsoory SG, Sklar P, State MW, Stein MB, Strakowski SM, Taylor SF, Turecki G, Turetsky BI, Weissman MM, Zachariou V, Zarate CA, Zubieta JK. Constance E. Lieber, Theodore R. Stanley, and the Enduring Impact of Philanthropy on Psychiatry Research. Biol Psychiatry 2016; 80:84-86. [PMID: 27346079 PMCID: PMC6150945 DOI: 10.1016/j.biopsych.2016.05.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 05/09/2016] [Accepted: 05/09/2016] [Indexed: 10/21/2022]
Affiliation(s)
- JH Krystal
- Department of Psychiatry and Neuroscience, Yale University School of Medicine, New Haven, Connecticut; Behavioral Health Services, Yale New Haven Hospital, New Haven, Connecticut; Clinical Neuroscience Division, VA Connecticut Healthcare System, West Haven, Connecticut; Departments of Psychiatry and Radiology, Columbia University, New York, New York.
| | - A Abi-Dargham
- The New York State Psychiatric Institute, New York, New York
| | - S Akbarian
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - AFT Arnsten
- Department of Psychiatry and Neuroscience, Yale University School of Medicine, New Haven, Connecticut; Child Study Center, Yale University School of Medicine, New Haven, Connecticut
| | - DM Barch
- Departments of Psychology and Radiology, Washington University in St. Louis, St. Louis, Missouri
| | - CE Bearden
- Departments of Psychiatry and Psychology and the Brain Research Institute, Semel Institute for Neuroscience and Human Behavior, University of California at Los Angeles, Los Angeles, California
| | - DL Braff
- Department of Psychiatry, University of California San Diego, San Diego, California
| | - ES Brown
- Department of Psychiatry, The University of Texas Southwestern Medical Center, Dallas, Texas
| | - ET Bullmore
- Department of Psychiatry and Behavioral and Neuroscience Institute, University of Cambridge, Cambridge, United Kingdom; ImmunoPsychiatry, GlaxoSmithKline, Cambridge, United Kingdom
| | - WA Carlezon
- Department of Psychiatry and Neuroscience, Harvard Medical School, McLean Hospital, Belmont, Massachusetts
| | - CS Carter
- Department of Psychiatry and Behavioral Sciences, Imaging Research Center, and Center for Neuroscience, University of California at Davis, Davis, California
| | - EH Cook
- Institute of Juvenile Research, Department of Psychiatry, University of Illinois at Chicago, Chicago, Illinois
| | - ZJ Daskalakis
- Temerty Centre for Therapeutic Brain Intervention, Mood and Anxiety Division Centre for Addiction and Mental Health, Toronto, Ontario, Canada; Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - RJ DiLeone
- Department of Psychiatry, Yale University, New Haven, Connecticut
| | - RS Duman
- Department of Psychiatry and Neuroscience, Yale University School of Medicine, New Haven, Connecticut
| | - AA Grace
- Departments of Neuroscience, Psychiatry, and Psychology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - AR Hariri
- Department of Psychology & Neuroscience, Duke University, Durham, North Carolina
| | - PJ Harrison
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom
| | - N Hiroi
- Departments of Psychiatry and Behavioral Sciences, Neuroscience, and Genetics, Albert Einstein College of Medicine, Bronx, New York
| | - PJ Kenny
- Department of Pharmacology & Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, New York
| | - JE Kleinman
- Genetic Neuropathology Section, Lieber Institute for Brain Development, and Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - AD Krystal
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, North Carolina
| | - DA Lewis
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - BK Lipska
- Human Brain Collection Core, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - SR Marder
- Semel Institute for Neuroscience, University of California at Los Angeles, Los Angeles, California; VA Desert Pacific Mental Illness Research, Education, and Clinical Center, Los Angeles, California
| | - GF Mason
- Departments of Radiology & Biomedical Imaging and Psychiatry, Yale University, School of Medicine, New Haven, Connecticut
| | - DH Mathalon
- Department of Psychiatry, University of California at San Francisco, San Francisco, California; Psychiatry Service, San Francisco VA Medical Center, San Francisco, California
| | - CA McClung
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - CJ McDougle
- Massachusetts General Hospital and MassGeneral Hospital for Children, Lurie Center for Autism, Lexington, Massachusetts; Department of Psychiatry, Harvard Medical School, Boston, Massachusetts
| | - AM McIntosh
- Division of Psychiatry, University of Edinburgh, Edinburgh, United Kingdom
| | - FJ McMahon
- Human Genetics Branch and Genetic Basis of Mood and Anxiety Disorders Section, National Institute of Mental Health, Intramural Research Program, Bethesda, Maryland
| | - K Mirnics
- Department of Psychiatry, Vanderbilt University, Nashville, Tennessee
| | - LM Monteggia
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, Texas
| | - R Narendran
- Departments of Radiology and Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - EJ Nestler
- Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York
| | - A Neumeister
- Mitsubishi Tanabe Pharma Development America, Inc., Jersey City, New Jersey
| | - MC O’Donovan
- MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, United Kingdom
| | - D Öngür
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, Massachusetts
| | - CM Pariante
- Departments of Psychology and Neuroscience, Institute of Psychiatry, King’s College London, London, United Kingdom; Psychiatry and Immunology Lab & Perinatal Psychiatry, The Maurice Wohl Clinical Neuroscience Institute, London, United Kingdom
| | - MP Paulus
- Laureate Institute for Brain Research, Tulsa, Oklahoma
| | - G Pearlson
- Departments of Psychiatry and Neurobiology, Yale University and Olin Neuropsychiatric Research Center, Hartford, Connecticut
| | - ML Phillips
- Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - DS Pine
- National Institute of Mental Health, Intramural Research Program, Bethesda, Maryland
| | - DA Pizzagalli
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts; McLean Imaging Center, McLean Hospital, Belmont, Massachusetts
| | - MV Pletnikov
- Departments of Neuroscience and Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - JD Ragland
- Department of Psychiatry and Behavioral Sciences, Imaging Research Center, University of California at Davis, Sacramento, California
| | - JL Rapoport
- Child Psychiatry Branch, Division of Intramural Research, National Institute of Mental Health, Bethesda, Maryland
| | - KJ Ressler
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, Massachusetts
| | - SJ Russo
- Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York
| | - G Sanacora
- Department of Psychiatry, Yale University, New Haven, Connecticut
| | - A Sawa
- Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - AF Schatzberg
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California
| | - Y Shaham
- Behavioral Neuroscience Branch, NIDA-IRP, Baltimore, Maryland
| | - SG Shamay-Tsoory
- Department of Psychology, University of Haifa, Mount Carmel, Haifa, Israel
| | - P Sklar
- Division of Psychiatric Genomics, Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York
| | - MW State
- Department of Psychiatry, University of California at San Francisco, San Francisco, California
| | - MB Stein
- Departments of Psychiatry and Family Medicine & Public Health, School of Medicine, University of California at San Diego, La Jolla, California
| | - SM Strakowski
- Department of Psychiatry, Dell Medical School, University of Texas at Austin, Austin, Texas
| | - SF Taylor
- Department of Psychiatry, University of Michigan, Ann Arbor, Michigan
| | - G Turecki
- Department of Psychiatry, McGill University, Montreal, Canada
| | - BI Turetsky
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - MM Weissman
- New York State Psychiatric Institute & Department of Psychiatry, College of Physicians and Surgeons of Columbia University, New York, New York
| | - V Zachariou
- Fishberg Department of Neuroscience, Mount Sinai School of Medicine, New York, New York
| | - CA Zarate
- Experimental Therapeutics and Pathophysiology Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland
| | - JK Zubieta
- Department of Psychiatry, University Neuropsychiatric Institute, University of Utah Health Sciences Center, Salt Lake City, Utah
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Kellermann T, Fox PT, Zilles K, Caspers S, Roski C, Laird AR, Turetsky BI, Eickhoff SB. Functional connectivity of the affective network. KLIN NEUROPHYSIOL 2012. [DOI: 10.1055/s-0032-1301479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Ehrlichman RS, Gandal MJ, Maxwell CR, Lazarewicz MT, Finkel LH, Contreras D, Turetsky BI, Siegel SJ. N-methyl-d-aspartic acid receptor antagonist-induced frequency oscillations in mice recreate pattern of electrophysiological deficits in schizophrenia. Neuroscience 2008; 158:705-12. [PMID: 19015010 DOI: 10.1016/j.neuroscience.2008.10.031] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 10/16/2008] [Accepted: 11/14/2008] [Indexed: 12/20/2022]
Abstract
INTRODUCTION Electrophysiological responses to auditory stimuli have provided a useful means of elucidating mechanisms and evaluating treatments in psychiatric disorders. Deficits in gating during paired-click tasks and lack of mismatch negativity following deviant stimuli have been well characterized in patients with schizophrenia. Recently, analyses of basal, induced, and evoked frequency oscillations have gained support as additional measures of cognitive processing in patients and animal models. The purpose of this study is to examine frequency oscillations in mice across the theta (4-7.5 Hz) and gamma (31-61 Hz) bands in the context of N-methyl-d-aspartic acid receptor (NMDAR) hypofunction and dopaminergic hyperactivity, both of which are thought to serve as pharmacological models of schizophrenia. EXPERIMENTAL PROCEDURES Electroencephalograms (EEG) were recorded from mice in five treatment groups that consisted of haloperidol, risperidone, amphetamine, ketamine, or ketamine plus haloperidol during an auditory task. Basal, induced and evoked powers in both frequencies were calculated. RESULTS Ketamine increased basal power in the gamma band and decreased the evoked power in the theta band. The increase in basal gamma was not blocked by treatment with a conventional antipsychotic. No other treatment group was able to fully reproduce this pattern in the mice. CONCLUSIONS Ketamine-induced alterations in EEG power spectra are consistent with abnormalities in the theta and gamma frequency ranges reported in patients with schizophrenia. Our findings support the hypothesis that NMDAR hypofunction contributes to the deficits in schizophrenia and that the dopaminergic pathways alone may not account for these changes.
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Affiliation(s)
- R S Ehrlichman
- Stanley Center for Experimental Therapeutics in Psychiatry, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104, USA
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Arnold SE, Han LY, Moberg PJ, Turetsky BI, Gur RE, Trojanowski JQ, Hahn CG. Dysregulation of olfactory receptor neuron lineage in schizophrenia. Arch Gen Psychiatry 2001; 58:829-35. [PMID: 11545665 DOI: 10.1001/archpsyc.58.9.829] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Growing evidence implicates abnormal neurodevelopment in schizophrenia. While neuron birth and differentiation is largely completed by the end of gestation, the olfactory epithelium (OE) is a unique part of the central nervous system that undergoes regeneration throughout life, thus offering an opportunity to investigate cellular and molecular events of neurogenesis and development postmortem. We hypothesized that OE neurons exhibit deviant progress through neurodevelopment in schizophrenia characterized by an increase in immature neurons. METHODS Olfactory epithelium was removed at autopsy from 13 prospectively assessed elderly subjects who had schizophrenia and 10 nonpsychiatric control subjects. Sections were immunolabeled with antibodies that distinguish OE neurons in different stages of development, including basal cells (low-affinity nerve growth factor receptor, p75NGFR), postmitotic immature neurons (growth-associated protein 43 [GAP43]), and mature olfactory receptor neurons (olfactory marker protein). Absolute and relative densities of each cell type were determined. RESULTS We observed a significantly lower density of p75NGFR basal cells (37%) in schizophrenia and increases in GAP43 + postmitotic immature neurons (316%) and ratios of GAP43 + postmitotic immature neurons to p75NGFR + cells (665%) and olfactory marker protein + mature neurons to p75NGFR + basal cells (328%). Neuroleptic-free schizophrenia subjects exhibited the highest GAP43 + postmitotic immature neuron values. CONCLUSIONS Abnormal densities and ratios of OE neurons at different stages of development indicate dysregulation of OE neuronal lineage in schizophrenia. This could be because of intrinsic factors controlling differentiation or an inability to gain trophic support from axonal targets in the olfactory bulb. While caution is necessary in extrapolating developmental findings in mature OE to early brain development, similarities in molecular events suggest that such studies may be instructive.
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Affiliation(s)
- S E Arnold
- Center for Neurobiology and Behavior, University of Pennsylvania, 142 Clinical Research Bldg, 415 Curie Blvd, Philadelphia, PA 19104, USA.
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Gur RC, Alsop D, Glahn D, Petty R, Swanson CL, Maldjian JA, Turetsky BI, Detre JA, Gee J, Gur RE. An fMRI study of sex differences in regional activation to a verbal and a spatial task. Brain Lang 2000; 74:157-170. [PMID: 10950912 DOI: 10.1006/brln.2000.2325] [Citation(s) in RCA: 199] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Sex differences in cognitive performance have been documented, women performing better on some phonological tasks and men on spatial tasks. An earlier fMRI study suggested sex differences in distributed brain activation during phonological processing, with bilateral activation seen in women while men showed primarily left-lateralized activation. This blood oxygen level-dependent fMRI study examined sex differences (14 men, 13 women) in activation for a spatial task (judgment of line orientation) compared to a verbal-reasoning task (analogies) that does not typically show sex differences. Task difficulty was manipulated. Hypothesized ROI-based analysis documented the expected left-lateralized changes for the verbal task in the inferior parietal and planum temporal regions in both men and women, but only men showed right-lateralized increase for the spatial task in these regions. Image-based analysis revealed a distributed network of cortical regions activated by the tasks, which consisted of the lateral frontal, medial frontal, mid-temporal, occipitoparietal, and occipital regions. The activation was more left lateralized for the verbal and more right for the spatial tasks, but men also showed some left activation for the spatial task, which was not seen in women. Increased task difficulty produced more distributed activation for the verbal and more circumscribed activation for the spatial task. The results suggest that failure to activate the appropriate hemisphere in regions directly involved in task performance may explain certain sex differences in performance. They also extend, for a spatial task, the principle that bilateral activation in a distributed cognitive system underlies sex differences in performance.
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Affiliation(s)
- R C Gur
- Brain Behavior Laboratory, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania, 19104, USA.
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Gur RE, Turetsky BI, Cowell PE, Finkelman C, Maany V, Grossman RI, Arnold SE, Bilker WB, Gur RC. Temporolimbic volume reductions in schizophrenia. Arch Gen Psychiatry 2000; 57:769-75. [PMID: 10920465 DOI: 10.1001/archpsyc.57.8.769] [Citation(s) in RCA: 260] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Neuroanatomic studies of schizophrenia have reported temporolimbic abnormalities. Most magnetic resonance imaging studies have evaluated small samples of primarily men with chronic schizophrenia. Our goal was to evaluate sex differences in segmented temporal lobe subregions with reliable parcellation methods, relating volume with clinical and neurocognitive parameters. METHODS Magnetic resonance imaging was performed in 100 patients with schizophrenia (58 men, 42 women; 39 neuroleptic naive, 61 previously treated) and 110 healthy controls (51 men, 59 women). Gray and white matter volumes of temporolimbic (hippocampus and amygdala) and neocortical regions (superior temporal gyrus and temporal pole) were examined. Symptoms, functioning, and neurocognition were assessed concurrently. RESULTS Hippocampal gray matter volume was reduced in men (7%) and women (8.5%) with schizophrenia. In the amygdala, however, decreased volume was evident for men (8%) whereas women (10.5%) had increased volume. Magnetic resonance imaging of the temporal pole showed decreased gray matter in men (10%) and women (8.5%). For the superior temporal gyrus, the decrease exceeded that of whole-brain only in men (11.5%). Volumes were largely uncorrelated with clinical measures, but higher hippocampal volumes were associated with better memory performance for all groups. Cortical volumes were associated with better memory performance in healthy women. CONCLUSIONS Schizophrenia is associated with reduced gray matter volume in temporolimbic structures. In men, reduction was manifested in all regions, whereas women showed decreased hippocampal volumes but increased amygdala volumes. The abnormalities are evident in patients with first-episode schizophrenia and correlate more strongly with cognitive performance than with symptom severity.
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Affiliation(s)
- R E Gur
- Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104, USA
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Gur RE, Cowell PE, Latshaw A, Turetsky BI, Grossman RI, Arnold SE, Bilker WB, Gur RC. Reduced dorsal and orbital prefrontal gray matter volumes in schizophrenia. Arch Gen Psychiatry 2000; 57:761-8. [PMID: 10920464 DOI: 10.1001/archpsyc.57.8.761] [Citation(s) in RCA: 282] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Converging neuroanatomic, neurophysiological, and neurobehavioral evidence implicate prefrontal subregions in schizophrenia. Neuroanatomic studies with magnetic resonance (MR) imaging enable regional volume parcellation. Inconsistent reports may relate to variable methods and small samples. We attempted to resolve volume differences within sectors of the prefrontal lobe in a large sample, relating volumes to clinical and neurocognitive features. METHODS Magnetic resonance imaging was performed in 70 patients with schizophrenia (40 men and 30 women; 29 neuroleptic naive and 41 previously treated) and 81 healthy controls (34 men and 47 women). Gray and white matter volumes of the dorsolateral, dorsomedial, orbitolateral, and orbitomedial prefrontal cortex were quantified. Symptoms, functioning, and neurocognition were assessed concurrently. RESULTS Reduced prefrontal gray matter volume was observed in patients. The reduction was evident for the dorsolateral area in men (9%) and women (11%), for the dorsomedial area only in men (9%), and for orbital regions only in women (23% and 10% for lateral and medial, respectively). The reduction of orbital volume in women was associated with poorer premorbid functioning, more severe negative symptoms, and depression. Volume of dorsal cortex was positively associated with better performance on abstraction and attention tasks across all groups. CONCLUSIONS Schizophrenia is associated with reduced gray matter volume in prefrontal cortex, which affects men and women in the dorsolateral sector. The effects are moderated by sex for dorsomedial and orbital regions and are related to symptom severity and cognitive function. This is not a by-product of treatment, since the differences are evident in neuroleptic-naive patients.
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Affiliation(s)
- R E Gur
- Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
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Matsui M, Gur RC, Turetsky BI, Yan MX, Gur RE. The relation between tendency for psychopathology and reduced frontal brain volume in healthy people. Neuropsychiatry Neuropsychol Behav Neurol 2000; 13:155-62. [PMID: 10910085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
OBJECTIVE We hypothesized that tendency toward psychopathology is associated with lower frontotemporal volumes. BACKGROUND Although there is considerable evidence for structural abnormalities in patients with major psychiatric disorders and increased recognition that neural substrates may underlie individual differences in personality, there have been no studies in healthy people attempting to relate personality to volumetric measures of brain structure. METHOD We used magnetic resonance imaging with an advanced method for automated segmentation of cranial compartments to gray matter, white matter, and cerebrospinal fluid. We examined the relation between frontal and temporal lobe volumes and Minnesota Multiphasic Personality Inventory measures of tendency toward psychopathology in 59 healthy individuals. RESULTS As hypothesized, higher scores on the clinical scales were associated with lower average frontal lobe volume. When the sample was divided according to sex, however, these correlations were significant in men (n = 29) but not in women (n = 30). The highest correlation was observed between lower frontal white matter volume in men and high schizophrenia scale score (r[27] = -0.59, p <0.001). CONCLUSIONS The findings suggest that personality dimensions in healthy people can be linked to neural substrates, which can potentially serve as endophenotypic markers of disposition to psychopathology. The sexually dimorphic effects are consistent with gender-related differences in the clinical manifestations of psychiatric disorders and may suggest sex hormone modulation of the psychopathologic processes.
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Affiliation(s)
- M Matsui
- Department of Psychiatry, University of Pennsylvania, Philadelphia, 19104, USA
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Ragland JD, Gur RC, Lazarev MG, Smith RJ, Schroeder L, Raz J, Turetsky BI, Alavi A, Gur RE. Hemispheric activation of anterior and inferior prefrontal cortex during verbal encoding and recognition: a PET study of healthy volunteers. Neuroimage 2000; 11:624-33. [PMID: 10860791 DOI: 10.1006/nimg.2000.0577] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Evidence of bilateral prefrontal activation during memory encoding and retrieval has increased attention given to anatomical subdivisions within the prefrontal cortex. The current study examined anterior and inferior aspects of the prefrontal cortex to determine their degree of functional and hemispheric overlap during encoding and recognition. Cerebral blood flow of 25 healthy volunteers was measured using PET (15)O-water methods during four conditions: resting baseline, sequential finger movement, word encoding, and word recognition. Resting and motor images were averaged to provide a single reference that was subtracted from encoding and recognition using statistical parametric mapping (SPM96). Memory conditions were also subtracted from each other to identify differences in regional activity. Subjects performed well (86% correct) and had a slightly conservative response bias. Baseline subtraction from encoding revealed focal activation of left inferior prefrontal cortex (area 45) without significant contralateral activation. Recognition minus baseline subtraction produced a focal right anterior prefrontal activation (areas 9 and 10) that was not present in the left hemisphere. Bilateral effects were seen in area 45 during recognition. Subtraction of memory tasks from each other did not reveal any areas of greater activity during encoding. However, the recognition task produced greater activation in right area 9 extending into the anterior cingulate. Greater activity during recognition was also observed in left insula and bilateral visual integration areas. These results are discussed in relation to the prevailing model of prefrontal hemispheric asymmetry during episodic memory.
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Affiliation(s)
- J D Ragland
- Department of Psychiatry, University of Pennsylvania Health Systems, Philadelphia, Pennsylvania, 19104, USA
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Abstract
OBJECTIVE The authors' goal in this study was to compare the size of olfactory bulbs of patients with schizophrenia and those of healthy subjects. METHOD Magnetic resonance imaging scans of olfactory bulbs were obtained from 26 patients with schizophrenia and 22 healthy comparison subjects. A reliable region of interest procedure was used to measure olfactory bulb volume. RESULTS Patients exhibited 23% smaller bilateral bulb volume than comparison subjects, independent of acute clinical, demographic, or treatment measures. Bulb volume correlated with odor detection sensitivity in healthy subjects but not in patients with schizophrenia. CONCLUSIONS Patients with schizophrenia exhibit structural olfactory deficits as well as functional olfactory deficits. The olfactory system may be a model system in which to study the neurobiology of the disorder.
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Affiliation(s)
- B I Turetsky
- Department of Psychiatry, Radiology, and Otorhinolaryngology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Abstract
BACKGROUND Reduced P300 amplitude is a robust finding in patients with schizophrenia. In previous investigations, we reported reductions of specific subcomponents of the auditory oddball P300 that were independent of acute symptomatology and persistent over time, consistent with a trait abnormality. To clarify whether these stable deficits represented genetic markers of vulnerability to schizophrenia, event-related brain potentials (ERPs) from patients were compared to those from their own healthy siblings and unrelated control subjects. METHODS Auditory P300 ERPs were acquired from 11 schizophrenic patients, 12 healthy siblings and 23 matched control subjects. Five P300 subcomponents were identified using current source density measures: frontal, bilateral parietal, and bilateral temporal. RESULTS Consistent with previous reports, patients had reduced parietal and frontal P300 amplitudes. The healthy siblings of the schizophrenic probands had an isolated reduction of the frontal P300. CONCLUSIONS Frontal P300 amplitude is a potential endophenotypic marker of genetic vulnerability to schizophrenia in individuals who otherwise show no evidence of clinical symptomatology. Given the functional interpretation of the frontal P300 as a physiological correlate of cognitive orienting, this supports the hypothesis that impairments of the neural substrate underlying attentional mechanisms are selective indicators of genetic susceptibility to schizophrenia in high-risk individuals.
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Affiliation(s)
- B I Turetsky
- Department of Psychiatry, University of Pennsylvania, Philadelphia, Philadelphia, Pennsylvania 19104, USA
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Abstract
BACKGROUND There is emerging evidence that gray matter (GM) is reduced in patients with schizophrenia. Information on the extent of global differences in the 3 principal supertentorial compartments is necessary for interpretation of regional effects. The relation of GM reduction to clinical status and neurocognition also requires examination. METHODS Magnetic resonance imaging, neurocognitive measures, and clinical assessment of symptoms and functioning were obtained for 130 patients (51 neuroleptic naive, 79 previously treated) and 130 healthy controls (75 men, 55 women in each group). RESULTS Overall GM volume was reduced in patients compared with controls. This was evident in men (6% reduction) and women (2% reduction) and was already evident at the first presentation of neuroleptic-naive patients. The reduction sustained correction for age and total intracranial volume. Compartmental volumes did not correlate with the severity of positive (r, -0.08 to 0.23) or negative (r, -0.01 to -0.07) symptoms, but GM volume was associated with better premorbid functioning in women (r, 0.36-0.51). Small but significant correlations (r, 0.19-0.44) were observed between GM volume and performance in 6 neurocognitive domains. These correlations varied by diagnosis, most higher in patients, and were moderated by sex. CONCLUSIONS Gray matter volume reduction in schizophrenia is already evident in men and women at first presentation. While this reduction is not correlated with symptom severity, it is associated with cognitive performance. Since GM development accelerates in the later part of gestation, while white matter growth is primarily postnatal, the results may support the hypothesis that neurodevelopmental processes relate to GM deficit.
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Affiliation(s)
- R E Gur
- Schizophrenia Research Center, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia 19104, USA.
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Abstract
Olfactory dysfunction in patients with schizophrenia has been a topic of increasing interest, with deficits in odor identification, detection threshold sensitivity, discrimination, and memory being reported. Despite increasing knowledge, controversy has existed about possible differential deficits among olfactory tests as well as the influences of gender, smoking, and medication status on olfactory measures. To help elucidate some of this controversy, we conducted a qualitative and quantitative (meta-analytic) review of the English language literature on olfaction in schizophrenia. Moderator variables such as gender, medication status, and smoking history were also examined. Results indicated that substantial olfactory deficits, across all domains, are observed in patients with schizophrenia. No differential deficits were observed across domains of odor identification, detection threshold sensitivity, discrimination, and memory. The influences of gender, medication status, and smoking on effect sizes were not significant across studies. This supports the hypothesis of primary dysfunction in the olfactory system that is regulated by brain regions where structural and functional abnormalities have also been reported in neuroimaging studies.
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Affiliation(s)
- P J Moberg
- Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, USA
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15
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Gur RC, Turetsky BI, Matsui M, Yan M, Bilker W, Hughett P, Gur RE. Sex differences in brain gray and white matter in healthy young adults: correlations with cognitive performance. J Neurosci 1999; 19:4065-72. [PMID: 10234034 PMCID: PMC6782697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Abstract
Sex-related differences in behavior are extensive, but their neuroanatomic substrate is unclear. Indirect perfusion data have suggested a higher percentage of gray matter (GM) in left hemisphere cortex and in women, but differences in volumes of the major cranial compartments have not been examined for the entire brain in association with cognitive performance. We used volumetric segmentation of dual echo (proton density and T2-weighted) magnetic resonance imaging (MRI) scans in healthy volunteers (40 men, 40 women) age 18-45. Supertentorial volume was segmented into GM, white matter (WM), and CSF. We confirmed that women have a higher percentage of GM, whereas men have a higher percentage of WM and of CSF. These differences sustained a correction for total intracranial volume. In men the slope of the relation between cranial volume and GM paralleled that for WM, whereas in women the increase in WM as a function of cranial volume was at a lower rate. In men the percentage of GM was higher in the left hemisphere, the percentage of WM was symmetric, and the percentage of CSF was higher in the right. Women showed no asymmetries. Both GM and WM volumes correlated moderately with global, verbal, and spatial performance across groups. However, the regression of cognitive performance and WM volume was significantly steeper in women. Because GM consists of the somatodendritic tissue of neurons whereas WM comprises myelinated connecting axons, the higher percentage of GM makes more tissue available for computation relative to transfer across distant regions. This could compensate for smaller intracranial space in women. Sex difference in the percentage and asymmetry of the principal cranial tissue volumes may contribute to differences in cognitive functioning.
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Affiliation(s)
- R C Gur
- Section of Neuropsychiatry, Department of Psychiatry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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16
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Abstract
While the P50 component (50-60-ms latency) of the auditory evoked potential has been reported as abnormal in schizophrenia, few studies have examined the relationship between this abnormality and clinical or neuropsychological measures. To examine these possible relationships, mid-latency auditory evoked potentials were recorded at the CZ recording site of 47 patients with schizophrenia in response to binaural clicks presented at three stimulus rates: 1, 5 and 10/sec. A sub-sample of patients were then divided into high- (n = 15) and low-P50 abnormality (n = 16) groups based on a median split of the P50 amplitude at a rate of 10/sec (a greater amplitude at this rate suggests a greater abnormality in recovery) of the entire sample. Only those patients with complete neuropsychological and clinical data and who were reasonably matched on demographic dimensions were included. A multivariate analysis of variance of 11 neuropsychological function profile scores showed a significant group x global score interaction (Hotelling t = 3.97, p < 0.005). The high-abnormality group had relatively greater deficits for attention profile scores than for the remaining neuropsychological measures. An analysis of global subscores for SAPS and SANS clinical measures revealed a significant difference only for the SANS attention subscale (p < 0.05). The high-abnormality group was rated as more severe on the attention measure. These convergent findings across both phenomenological and neuropsychological measures suggest that abnormalities in P50 recovery may be linked to deficits in attention processes in schizophrenia.
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Affiliation(s)
- R J Erwin
- Department of Psychiatry, University of Pennsylvania, Philadelphia 19104, USA.
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17
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Gur RE, Cowell P, Turetsky BI, Gallacher F, Cannon T, Bilker W, Gur RC. A follow-up magnetic resonance imaging study of schizophrenia. Relationship of neuroanatomical changes to clinical and neurobehavioral measures. Arch Gen Psychiatry 1998; 55:145-52. [PMID: 9477928 DOI: 10.1001/archpsyc.55.2.145] [Citation(s) in RCA: 389] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Cross-sectional neuroanatomical studies have reported abnormalities in schizophrenia that relate to disease variables. Longitudinal neuroimaging investigations that integrate anatomical, clinical, and neurobehavioral measures may help clarify the pathogenesis of schizophrenia. METHODS Magnetic resonance brain imaging and neurobehavioral studies were conducted at baseline and after 30.63 +/- 12.92 months (mean +/- SD) in 40 patients with schizophrenia (23 men and 17 women) and 17 healthy controls (13 men and 4 women). The schizophrenia group included 20 first-episode and 20 previously treated subjects. Volumes of whole-brain, cerebrospinal fluid, and frontal and temporal lobes were measured. The severity of negative and positive symptoms was assessed, medications were monitored, and neurobehavioral functioning in 8 domains was evaluated. RESULTS Both first-episode and previously treated patients had smaller brains and frontal and temporal lobes than controls at intake. Longitudinally, reduction in frontal lobe volume was found only in patients, whereas temporal lobe reduction was also seen in controls. The association between volume reduction and symptom changes differed between patient groups, but volume reduction was associated with decline in some neurobehavioral functions in both groups. Exploratory analysis suggested that neuroleptic dose is correlated with changes in all 3 domains. CONCLUSIONS The existence of neuroanatomical and neurobehavioral abnormalities in patients with first-episode schizophrenia indicates that the brain dysfunction occurred before clinical presentation. However, there is also evidence of progression, in which anatomical changes may affect some clinical and neurobehavioral features of the illness in some patients.
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Affiliation(s)
- R E Gur
- Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, USA
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18
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Turetsky BI, Colbath EA, Gur RE. P300 subcomponent abnormalities in schizophrenia: I. Physiological evidence for gender and subtype specific differences in regional pathology. Biol Psychiatry 1998; 43:84-96. [PMID: 9474441 DOI: 10.1016/s0006-3223(97)00258-8] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND P300 event-related brain potential (ERP) amplitude is reduced in patients with schizophrenia. Little attention has been paid to gender differences underlying this abnormality, despite clinical differences between male and female schizophrenics. Studies have also largely ignored the fact that the P300 represents the activity of multiple neural generators and have not assessed the separate activity of different subcomponents. METHODS Auditory P300 ERPs were recorded from 65 patients (42 male, 23 female) and 48 controls (30 male, 18 female). Positive and negative symptoms were assessed with standardized rating scales, and patients were subtyped as deficit or nondeficit. Five P300 subcomponents were identified using current source density measures: frontal (P3f), bilateral parietal (P3pL, P3pR), and bilateral temporal (P3tL, P3tR). RESULTS Three subcomponents (P3tL, P3f, P3pR) were reduced in patients. The left temporal (P3tL) deficit was common across patient groups, but the overall profile of P300 abnormalities varied by gender and deficit/nondeficit status. Women had greater P3tL and P3f decrements; P3pR was abnormal in men. Deficit and nondeficit patients resembled men and women, respectively, independent of gender. P3f and P3tL amplitudes were correlated and unrelated to symptomatology. P3pR was related to Brief Psychiatric Rating Scale score. CONCLUSIONS A left temporal abnormality exists in schizophrenia, along with two different profiles of regional pathology, which segregate by gender and deficit/nondeficit status. This supports the hypothesis of two distinct illness subtypes and suggests a physiological basis for phenotypic gender and deficit/nondeficit differences. P300 subcomponent abnormalities may serve as subtype markers. Correlated left temporal and frontal dysfunction is consistent with a frontotemporal neural network disturbance in some schizophrenics. Further investigation of the longitudinal stability and familial inheritance of these subcomponent abnormalities is warranted.
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Affiliation(s)
- B I Turetsky
- Department of Psychiatry, University of Pennsylvania, Philadelphia 19104, USA
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19
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Moberg PJ, Doty RL, Turetsky BI, Arnold SE, Mahr RN, Gur RC, Bilker W, Gur RE. Olfactory identification deficits in schizophrenia: correlation with duration of illness. Am J Psychiatry 1997; 154:1016-8. [PMID: 9210756 DOI: 10.1176/ajp.154.7.1016] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE The authors examined the relationship between deficits in olfactory identification and duration of illness in young and elderly patients with schizophrenia. METHOD Olfactory identification performance of 38 patients with schizophrenia and 40 normal subjects was compared by using the University of Pennsylvania Smell Identification Test. RESULTS The schizophrenic patients demonstrated olfactory deficits relative to the comparison group, and the elderly schizophrenic patients displayed a greater magnitude of olfactory deficit than the younger patients. Independent of normal aging effects and cognitive deficit, patients with schizophrenia showed a strong relationship between olfactory identification scores and duration of illness, which suggests that olfactory abilities decline progressively over the course of the disorder. CONCLUSIONS In contrast to other neuropsychological measures that have been reported to be stable over the course of illness, olfactory identification abilities deteriorate steadily in patients with schizophrenia, even for those with relatively recent onset.
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Affiliation(s)
- P J Moberg
- Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, USA
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20
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Abstract
In the present study we assessed olfactory identification ability using the University of Pennsylvania Smell Identification Test (UPSIT) in 16 elderly patients with schizophrenia (ES), 20 patients with a diagnosis of probable Alzheimer's disease (AD), and 20 healthy elderly controls (EC). Both patient groups exhibited marked deficits in UPSIT performance relative to controls. ES and AD patients with similar levels of general cognitive impairment did not differ on the UPSIT, suggesting that the two disorders may share a common dysfunction in olfactory brain regions. While there have been recent reports of greater olfactory impairment in males, neither patient group exhibited significant gender differences on the UPSIT.
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Affiliation(s)
- P J Moberg
- Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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21
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Abstract
BACKGROUND The impact of aging and of gender has been examined in health and disease, but has received limited attention in schizophrenia. A lifespan perspective of gender differences can contribute to an understanding of clinical features and their underlying neurobiological processes. METHOD A prospective sample of 272 patients with schizophrenia, divided into four age groups: < 35, 35-65, 65-80 and > 85, was assessed with standardized procedures to measure the composition and severity of symptoms. RESULTS Aging was associated with increased severity of symptoms and gender differences were noted. Negative symptoms increased in severity, while some positive symptoms ameliorated with aging. Women were characterized by reduced negative symptoms, and this remained evident until the eighth decade. CONCLUSIONS Aging and gender moderate the clinical features of schizophrenia in specific symptom clusters. These effects may give insight into neurobiological substrates of the illness.
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Affiliation(s)
- R E Gur
- Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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22
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Abstract
OBJECTIVE The purpose of this study was to investigate sex differences in relationships between brain and behavior in schizophrenia. METHOD Frontal lobe, temporal lobe, and whole brain volumes were obtained from magnetic resonance images of 91 patients with schizophrenia (54 men and 37 women) and 114 healthy comparison subjects (62 men and 52 women). Four independent symptom scales, based on the following symptom clusters, were derived from clinical data: negative, disorganization, Schneiderian hallucinations-delusions, and suspicion-hostility. Regression analyses incorporating the four clinical scales and neuroanatomical volumes were performed to investigate possible interactions between brain region and sex. RESULTS Significant interactive effects of sex and frontal lobe volume were found in regression analyses of the disorganization and suspicion-hostility symptom scales. In men, higher frontal lobe volume was associated with milder severity of disorganization but was not correlated with severity of suspicion-hostility. In women, higher frontal lobe volume was associated with more severe disorganization as well as more severe suspicion-hostility. No associations were found between brain volume and severity of negative or Schneiderian symptoms. CONCLUSIONS Differences between male and female patients were observed in the relationships between frontal lobe volume and two of the four clinical dimensions examined. These findings suggest that aspects of the neuropathological basis for some symptoms of schizophrenia may be sexually dimorphic.
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Affiliation(s)
- P E Cowell
- Department of Psychiatry, University of Pennsylvania, Philadelphia 19104, USA
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23
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Mahr RN, Moberg PJ, Overhauser J, Strathdee G, Kamholz J, Loevner LA, Campbell H, Zackai EH, Reber ME, Mozley DP, Brown L, Turetsky BI, Shapiro RM. Neuropsychiatry of 18q- syndrome. Am J Med Genet 1996; 67:172-8. [PMID: 8723044 DOI: 10.1002/(sici)1096-8628(19960409)67:2<172::aid-ajmg7>3.0.co;2-u] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Our understanding of neuropsychiatric abnormalities in patients with deletions of the long arm of chromosome 18 (18q- syndrome) is based mainly on sporadic case reports. We characterized the neuropsychiatric phenotype in 27 patients across a wide age range (2-47 years) with breakpoints ranging from 18q22.3-18q21.2. Adaptive behavior scores (Vineland Composite) were significantly higher in females than in males (62 +/- 5 vs. 43 +/- 3). Intelligence ranged from borderline to severely deficient (IQ, 73- < 40), with academic achievement similarly impaired. Performance in specific neuropsychological functions, including attention, novel problem solving, memory, language, visuomotor integration, and fine motor dexterity, was consistently in the moderately-to-severely impaired range. Behavioral problems were common in both sexes, including aggressivity, hyperactivity, and temper tantrums. Contrary to the few previous reports, we found no evidence of psychosis in any patients. In a subset of patients selected on the basis of no prior knowledge of behavioral problems, 1 of 16 patients (6%) had autism, as defined by the Autistic Diagnostic Interview--Revised (ADI-R) [Lord et al., 1994: J Autism Dev Disord 24:659-685]. Thus, the prevalence of autism in 18q- syndrome is probably no greater than that in other developmental disabilities with a similar level of cognitive impairment. In contrast to what has been believed since 18q- was first described 30 years ago, we found no relationship between chromosome deletion size and any measure of cognition or behavior; nor were there any correlations between any of these measures with the presence or absence of abnormalities on MRI or somatosensory-evoked potentials.
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Affiliation(s)
- R N Mahr
- Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, USA
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Cowell PE, Turetsky BI, Gur RC, Grossman RI, Shtasel DL, Gur RE. Sex differences in aging of the human frontal and temporal lobes. J Neurosci 1994; 14:4748-55. [PMID: 8046448 PMCID: PMC6577197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
This study investigated effects of age and sex on regional brain structure in humans, focusing on the frontal and temporal lobes. Hemispheric volumes were obtained from magnetic resonance images (MRIs) of 96 young (53 men, 43 women; aged 18-40 years) and 34 older (17 men, 17 women; aged 41-80) healthy volunteers. Images (5 mm axial spin-echo, repetition time of 3000 msec and echo times of 30 and 80 msec) were resliced along the anterior commissure-posterior commissure (AC-PC) axis to standardize for difference in head tilt, and imported into a computer program where borders of the frontal and temporal lobes were delineated. The program calculated regional brain volumes based on slice data from which CSF was segmented out. An age x sex x hemisphere x region interaction indicated that age-related reductions in brain volume were sexually dimorphic, lateralized, and region specific. Greater decrements in brain volume occurred with age in the frontal lobe than in the temporal lobe. Age-related reductions in both regions were greater in men than in women, demonstrating that sexual dimorphisms in human neuroanatomy are not fixed, but continue to change throughout adulthood. The possibility that gonadal hormones play a role in the promotion and/or prevention of neural atrophy with aging is discussed.
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Affiliation(s)
- P E Cowell
- Department of Psychiatry, University of Pennsylvania, Philadelphia 19104
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25
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Abstract
An analytic method has recently been proposed for partitioning scalp-recorded EEG and evoked potential (EP) data into parts arising from deep (i.e., subcortical) vs. superficial (i.e., cortical) sources. The method is based on the observation that the current source density (CSD) is selectively sensitive to electrical activity arising from superficial sources, and the conjecture that the residual potential which remains after subtracting the CSD from the scalp potentials, represents activity from deep sources. We investigated the validity of this procedure by simulating scalp potential data for superficial and deep dipole sources with known locations and orientations. Our single-dipole simulations demonstrated that, when the actual location of the source was superficial, the partitioning procedure erroneously attributed a sizeable proportion of the total topographic variance to the activity of deeper sources. This produced a consistent bias in the simulations with two dipoles, when both superficial and deep sources were present. In such cases, the relative contribution of the deeper source was consistently overestimated, and the scalp topography of the deep source activity was profoundly misrepresented by the residual which results from subtracting the CSD from the scalp potential. We conclude that the proposed method for partitioning EEG and EP data into components arising from deep vs. superficial intracranial sources is not valid.
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Affiliation(s)
- B I Turetsky
- Department of Psychiatry, Medical College of Pennsylvania, Philadelphia 19129
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26
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Abstract
Averaging single trial evoked potential data to produce an estimate of the underlying signal obscures trial-to-trial variation in the response. We describe a method for estimating slow changes in the evoked potential signal by smoothing the data over trials. We discuss the crucial issue of deciding how much to smooth and suggest that an appropriate smoothing parameter is one that minimizes the estimated mean average square error of the smoothed data. Equations to estimate the mean average square error for a one-dimensional local linear regression smoother are presented. Performance of the method is assessed using simulated evoked potential data with several different models of a changing signal and different values of the signal-to-noise ratio. We find that the method rarely imputes trial-to-trial variation to data sets that have an unchanging signal, while it almost always produces less error than averaging when estimating a varying signal. The ability of the method to reveal signal heterogeneity is hampered by very low signal-to-noise ratios. When applied to real auditory evoked potential data from a sample of elderly subjects, the method indicated a changing signal in 35% of all subjects and in 56% of subjects with signal-to-noise ratios above 0.6. Consistent patterns of variation in the auditory evoked potential were present in this sample.
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Abstract
Signal power, noise power and their ratio (SNR) are important variables underlying estimation of evoked potential signals, yet, they are rarely explicitly considered in the design or analysis of EP experiments. A model is developed which relates the reliability of the average evoked potential (AEP) wave form to signal power, noise power, SNR, and the number of single trials included in the average. Measurements taken from auditory and visual EP experiments in elderly subjects show that noise power is highly reliable across experimental conditions and probably reflects global CNS anatomic or physiologic factors. In contrast, signal power and SNR are variable across conditions and sensory modalities, but are stable across replications. Thus signal power reflects CNS processes specific to the experimental paradigm. These results have importance for EP estimation. The expected reliability of the AEP cannot be adequately predicted from estimates of a subject's noise power, or from SNR estimated under different experimental conditions. These findings suggest the need for on-line estimation of SNR during data acquisition to ensure adequate reliability of AEPs.
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