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At least 973 records · Page 54Linked to original sources
PubMed2026

Bidirectional causal relationships between plasma proteins, neuroimaging metrics and risk of Alzheimer's disease.

BACKGROUND: Changes in neuroimaging metrics are among the first detectable pathophysiological alterations in Alzheimer's disease (AD). Proteins are closely linked to fluctuations in neuroimaging metrics. Therefore, the analysis of the proteomic signature associated with neuroimaging metrics holds significant promise for uncovering therapeutic targets that contribute to AD. METHODS: GWAS data concerning the Brain Imaging Data Structure (BIDs). The AD cohort comprised a total of 401,661 individuals diagnosed with AD, alongside 10,520 control participants. For a bidirectional MR analysis involving neuroimaging metrics, proteomics, and AD, the methods utilized included inverse variance weighted (IVW), MR Egger, weighted median, weighted mode, and the Wald ratio approaches. RESULTS: We identified 12 neuroimaging metrics that demonstrate significant relevance to AD (thickness of the left total hemisphere, volume of the right thalamus, and et al.). These metrics are structural magnetic resonance imaging (MRI) biomarkers that remain stable throughout the entire course of AD, from the preclinical stage through mild cognitive impairment (MCI) to dementia. Additionally, we found a substantial number of 1633 proteins that also show a noteworthy causal relationship with AD. Functional enrichment analysis indicated that these proteins were predominantly focused within various pathways linked to AD, encompassing those involved in the synaptic vesicle cycle, synaptic membranes, neurotransmitter release, and the activity of GABA receptors. In addition, our research indicates that the significant relationships observed between the identified proteins and AD are influenced by neuroimaging metrics. Notably, we found that these neuroimaging metrics play a crucial role in mediating a substantial 67% of the inverse relationship that exists between PTPRC and the phenotypic characteristics associated with AD. CONCLUSIONS: This study successfully establishes a connection between proteomic and neuroimaging metrics, as well as the AD that influence them. By creating this relationship, the research offers important information that aids in comprehending the intricate mechanisms involved in AD.

Alzheimer Disease↗
PubMed2004

Bilateral hippocampal volume predicts verbal memory function in temporal lobe epilepsy.

The present study used quantitative volume estimates of the hippocampus based on structural magnetic resonance imaging (MRI) to predict memory performance of individuals with epilepsy of temporal lobe origin (TLE). Twenty individuals with TLE completed standardized neuropsychological tests and a quality of life inventory, and participated in a brain MRI protocol designed to obtain high-resolution images of the hippocampus. The combined volume of the left and right hippocampi was found to be the best predictor of objective verbal memory performance. This finding is consistent with the functional adequacy model of hippocampal function. In contrast, the asymmetry between right and left hippocampal volume was the best predictor of subjective ratings of cognitive functioning, which is consistent with the functional reserve model. The collective and complementary functions of the left and right hippocampi merit further exploration in prospective studies of memory function and TLE.

Adult↗
PubMed2003

Abnormal cerebral asymmetry and schizophrenia in a subject with Klinefelter's syndrome (XXY).

BACKGROUND: A high incidence of schizophrenia has been reported in individuals with sex chromosome aneuploides (SCAs), and extra-X aneuploidy appears to adversely affect neurodevelopment. We previously examined neurodevelopment in SCA subjects with structural magnetic resonance imaging (MRI) of the brain. We present an XXY subject who subsequently developed schizophrenia. Further examination of the MRI data was undertaken. METHODS: Graphs of MRI-determined regional brain to whole brain volume proportions and cerebral asymmetry indexes were generated for Klinefelter (n = 10) and male control subjects (n = 25) to allow inter-individual comparisons. RESULTS: The index case had reversed prefrontal and temporal lobe asymmetries, and these findings were more marked than in any other subject. CONCLUSIONS: It has been suggested that a genetic locus for schizophrenia may be found on the X chromosome and that the gene(s) concerned are implicated in the development of normal cerebral asymmetries. This case supports these arguments.

Adolescent↗
PubMed1997

Subcortical hyperintensities on magnetic resonance imaging in patients with severe depression--a longitudinal evaluation.

In a longitudinal evaluation of 37 patients with severe depression who had undergone brain magnetic resonance imaging (MRI) 6 months-2 years (mean 14.1 months) previously, the degree of residual dysfunction was predicted by the extent of subcortical white matter hyperintensities (WMHS, p < .01), longer time elapsed since the MRI scan (p < .05), older age (p < .05), and older age at onset of affective disorder (p < .05). Ten (27%) patients developed "probable" dementia syndromes of the vascular type, with such syndromes being predicted by WMHS (p < .01) and older age of onset of affective disorder (p < .05). Institutionalization of patients was predicted largely by the combination of chronic depression, progressive cognitive decline, and advanced age. The study supports the notion that a subgroup of patients with late-onset depressive disorders, without a family history of depression, and with risk factors to cerebrovascular disease, have extensive WMHS on MRI, and that such structural brain changes predispose to chronic depression and progressive cognitive decline.

Adult↗
PubMed1997

Distributed system for processing 3D medical images.

Three-dimensional (3D) image data generated by radiological imaging modalities such as CT and MRI can provide detailed structural insight. Automating the analysis of these images can improve the consistency of the results and reduce user interaction time, but introduces a tremendous computational burden. To address this problem, we have designed a distributed processing environment for the rapid processing of 3D medical images. Our system allows a user to perform automatic 3D filtering, segmentation, and measurement on a 3D image using a heterogeneous network of processors and the PVM protocol.

Computer Communication Networks↗
PubMed1999

Bridging cognition, the brain and molecular genetics: evidence from Williams syndrome.

Williams syndrome (WMS) is a rare sporadic disorder that yields a distinctive profile of medical, cognitive, neurophysiological, neuroanatomical and genetic characteristics. The cognitive hallmark of WMS is a dissociation between language and face processing (relative strengths) and spatial cognition (profound impairment). Individuals with WMS also tend to be overly social, behavior that is opposite to that seen in autism. A genetic hallmark of WMS is a deletion on chromosome band 7q11.23. Williams syndrome is also associated with specific neuromorphological and neurophysiological profiles: proportional sparing of frontal, limbic and neocerebellar structures is seen using MRI; and abnormal functional organization of the neural systems that underlie both language and face processing is revealed through studies using event-related potentials. The non-uniformity in the cognitive, neuromorphological and neurophysiological domains of WMS make it a compelling model for elucidating the relationships between cognition, the brain and, ultimately, the genes.

Brain↗
PubMedDate not supplied

Clinical brain proton magnetic resonance spectroscopy for management of Alzheimer's and sub-cortical ischemic vascular dementia in older people.

This study examined the clinical usefulness of magnetic resonance spectroscopy (MRS) performed using an automated single voxel technique at 1.0 T field strength in a district general hospital magnetic resonance (MR) scanner in the assessment of older people referred to a memory clinic with suspected dementia. Of 50 elderly subjects (M:F 20:30) examined and followed-up clinically over more than 2 years, 20 had clinical Alzheimer's disease (AD), 18 had clinical vascular dementia, six had mixed features and three were normal. Three normal volunteers were also studied. MRS was performed at the same time as structural magnetic resonance imaging (MRI), added <15 min to the examination and was well-tolerated in all patients studied. Patients with AD had significantly higher myoinositol/creatine (MI/Cr) ratios (mean +/- S.D.: 0.82 +/- 0.04) compared to those with vascular dementia (mean +/-S. D.: 0.71 +/- 0.07, P<0.00001) and normal subjects (mean +/- S.D.: 0.72 +/- 0.036, P<0.0002); there was little overlap between the AD and vascular groups. The mixed dementia group also had significantly higher MI/Cr ratios (mean +/- S.D.: 0.80 +/- 0.05) than vascular dementia (P<0.01) and normal (P<0.03) groups, but with considerable overlap. No significant differences were shown for N-acetyl aspartate or choline/creatine ratios between the different clinical groups. These data suggest that MI/Cr ratios can distinguish patients with AD from normal subjects and those with sub-cortical ischemic vascular dementia and that MRS will be useful to clinicians managing persons with AD in a district general hospital setting.

Journal Article↗
PubMed2001

Source localisation of 62-electrode human laser pain evoked potential data using a realistic head model.

Laser evoked potentials (LEPs), elicited by painful laser stimulation of the right forearm, were recorded from 62 electrodes in a single healthy subject. The positions of the electrodes on the scalp were co-registered with the subject's structural magnetic resonance image (MRI) of the brain. Spatio-temporal dipole modelling, using a head model derived from the MRI, estimated sources in left posterior cingulate, posterior parietal and anterior insular cortices. The parietal source peaked in activity at 260 ms, which explained the N1/N2 peaks of the LEPs. The cingulate source was the most strongly activated, at 400 ms, and accounted for the P2 LEP component. The insular source showed late, prolonged activation, peaking in magnitude at 850 ms. This is the first study to report scalp-recorded LEP generators in posterior parietal and insular cortices. Although these sources require replication, they are consistent with other functional imaging studies.

Brain Mapping↗
PubMed2000

Nuclear imaging methods for non-invasive drug monitoring.

Functional imaging techniques provide complimentary information to that provided by structural studies such as MRI and CT. Functional imaging is based upon known parameters such as physiology, metabolism, biochemistry, pharmacology, and any other biological process. As such, this methodology plays a major role in understanding the basic mechanisms of a multitude of disorders, accurate diagnosis of certain diseases, and developing effective treatment for serious illnesses such as cancer and central nervous system maladies. Although this type of imaging can be performed with various modalities, nuclear procedures have played the leading role in this discipline. Advances made in labeling various radionuclides to biologically important compounds, and development of sophisticated instruments have substantially contributed to the growth of the field of functional imaging. The introduction of positron emission topography (PET), which is based on imaging of compounds labeled with elements such as carbon, nitrogen, and fluorine, has added a major dimension to the evolution of the discipline. This review deals with a brief introduction to the methodologies utilized with radiolabeled tracers and then deals with specific applications of this technology. These applications include assessment of blood flow and metabolism, receptor imaging, elucidating the pathophysiologic process, evaluating role of labeled therapeutic agents, and the potential of these techniques in the development of novel biologic therapies. Functional imaging with radiolabeled tracers will play an increasingly important role in modern medicine, and its impact will be substantial in the management of patients with various disorders.

Drug Monitoring↗
PubMed2003

Caudal cingulate cortex involvement in pain processing: an inter-individual laser evoked potential source localisation study using realistic head models.

Electrophysiological studies have revealed a source of laser pain evoked potentials (LEPs) in cingulate cortex. However, few studies have used realistically shaped head models in the source analysis, which account for individual differences in anatomy and allow detailed anatomical localisation of sources. The aim of the current study was to accurately localise the cingulate source of LEPs in a group of healthy volunteers, using realistic head models, and to assess the inter-individual variability in anatomical location. LEPs, elicited by painful CO(2) laser stimulation of the right forearm, were recorded from 62 electrodes in five healthy subjects. Dipole source localisation (CURRY 4.0) was performed on the most prominent (P2) peak of each LEP data set, using head models derived from each subject's structural magnetic resonance image (MRI).For all subjects, the P2 LEP peak was best explained by a dipole whose origin was in cingulate cortex (mean residual variance was 3.9+/-2.4 %). For four out of five subjects, it was located at the border of the caudal division of left anterior cingulate cortex (area 24/32') with left posterior cingulate cortex (area 23/31). For the fifth subject the dipole was centred in right posterior cingulate cortex (area 31). This study demonstrates that the location of the cingulate source of LEPs is highly consistent across subjects, when analysed in this way, and supports the involvement of caudal cingulate regions in pain processing.

Adult↗
PubMed2002

Prefrontal cortical volume reduction associated with frontal cortex function deficit in 6-week abstinent crack-cocaine dependent men.

BACKGROUND: This study examined regional cortical volumes in 6-week abstinent men dependent on crack-cocaine only (Cr) or on both crack-cocaine and alcohol (CrA). Our goal was to test the a priori hypothesis of prefrontal cortical volume reduction, along with associated impairments in frontal mediated functions, and to look for differences between the Cr and CrA groups. METHODS: Structural magnetic resonance imaging (MRI) of the brain and neuropsychological assessment were performed on 17 6-week abstinent Cr subjects, 29 six-week abstinent CrA subjects, and 20 normal controls. Cortical volume was quantified in the prefrontal, parietal, temporal and occipital regions. RESULTS: Cr and CrA subjects showed comparable reductions in prefrontal gray matter volume compared to controls; this reduction was negatively associated with performance impairments in the executive function domain. CONCLUSIONS: Dependence on Cr (with or without concomitant alcohol dependence) was associated with reduced prefrontal cortical volume. Cr dependence with concomitant alcohol dependence was not associated with greater prefrontal volume reductions than Cr dependence alone. The existence of these findings at 6-week abstinence indicates that they are not a result of acute cocaine or alcohol exposure. The association of reduced prefrontal cortical volume with cognitive impairments in frontal cortex mediated abilities suggests that this reduced cerebral volume has functional consequences.

Adult↗
PubMed1999

A modified fuzzy clustering algorithm for operator independent brain tissue classification of dual echo MR images.

Methods for brain tissue classification or segmentation of structural magnetic resonance imaging (MRI) data should ideally be independent of human operators for reasons of reliability and tractability. An algorithm is described for fully automated segmentation of dual echo, fast spin-echo MRI data. The method is used to assign fuzzy-membership values for each of four tissue classes (gray matter, white matter, cerebrospinal fluid and dura) to each voxel based on partition of a two dimensional feature space. Fuzzy clustering is modified for this application in two ways. First, a two component normal mixture model is initially fitted to the thresholded feature space to identify exemplary gray and white matter voxels. These exemplary data protect subsequently estimated cluster means against the tendency of unmodified fuzzy clustering to equalize the number of voxels in each class. Second, fuzzy clustering is implemented in a moving window scheme that accommodates reduced image contrast at the axial extremes of the transmitting/receiving coil. MRI data acquired from 5 normal volunteers were used to identify stable values for three arbitrary parameters of the algorithm: feature space threshold, relative weight of exemplary gray and white matter voxels, and moving window size. The modified algorithm incorporating these parameter values was then used to classify data from simulated images of the brain, validating the use of fuzzy-membership values as estimates of partial volume. Gray:white matter ratios were estimated from 20 twenty normal volunteers (mean age 32.8 years). Processing time for each three-dimensional image was approximately 30 min on a 170 MHz workstation. Mean cerebral gray and white matter volumes estimated from these automatically segmented images were very similar to comparable results previously obtained by operator dependent methods, but without their inherent unreliability.

Adult↗
PubMed2000

Reduced regional cerebral blood flow in non-psychotic violent offenders.

The present study was designed to replicate previously reported findings of abnormal frontal and/or temporal cerebral blood flow in violent offenders and to control for the influence of major mental disorder (MMD), substance abuse, and current medication. HMPAO-SPECT-CBF and MRI scans from pretrial forensic psychiatric investigations of 21 subjects convicted of impulsive violent crimes were retrospectively re-evaluated. In 16/21 subjects, visual assessment of SPECT scans showed some hypoperfusion in the temporal and/or frontal lobes. MRI showed no corresponding structural damage. Quantified regional cerebral blood flow (rCBF) in defined regions of interest was compared between index cases and 11 healthy control subjects. Index subjects had significant reductions in the right angular gyrus and the right medial temporal gyrus, bilaterally in the hippocampus, and in the left white frontal matter, but they had significantly increased rCBF in the parietal association cortex bilaterally. The aberrations were as frequent and severe among the subjects without MMD, substance abuse, and current medication (n=7) as in the entire group of index subjects.

Adolescent↗
PubMed2002

Positron emission tomography imaging of brain tumors.

A wide variety of metabolic features of brain tumors can be imaged using PET, including glucose metabolism, blood flow, oxygen consumption, amino acid metabolism, and lipid synthesis. Currently, FDG is the most widely available PET tracer for body imaging and brain imaging. Malignant brain tumors, like many other soft tissue tumors, show increased glucose metabolism, which is reflected on FDG-PET imaging. FDG-PET imaging of brain tumors provides information on tumor grade and prognosis. Compared with other organ systems, FDG-PET imaging of the brain presents unique challenges because of the high background glucose metabolism of normal gray matter structures. Coregistration of the MRI (or CT) and FDG-PET images is essential for accurate evaluation of brain tumors and is performed routinely at the authors' institution. The heterogeneous nature of gliomas can result in significant sampling errors when patients are biopsied for primary tumor diagnosis or recurrent disease. FDG-PET can be used to define the most metabolically active targets for stereotactic biopsy. This in turn can improve diagnostic accuracy and reduce the number of biopsy samples required. FDG-PET is also useful for evaluating residual or recurrent tumor following therapy, and can be used to survey patients with low-grade brain tumors for evidence of degeneration into high-grade malignancy. In the case of suspected tumor recurrence or progression, PET can aid in defining appropriate targets for biopsy. One limitation of FDG-PET is the occasional inability to distinguish radiation necrosis from recurrent high-grade tumor. A second limitation is that FDG-PET is less sensitive than contrast-enhanced MRI for detecting intracranial metastases, and it is the authors' experience that brain studies should not be included as part of routine whole-body PET studies. Other tracers, such as 11C-methionine and FCH, also avidly accumulate in brain tumors and have the advantage of low background cortical activity. The relationship between degree of uptake of these agents and tumor grade is not established. These tracers may be useful in specific clinical situations, however, such as tumor localization for treatment planning or evaluation of low-grade tumors.

Blood Volume↗
PubMed2003

The morphometry of auditory cortex in the congenitally deaf measured using MRI.

The study of congenitally deaf individuals provides a unique opportunity to understand the organization and potential for reorganization of human auditory cortex. We used magnetic resonance imaging (MRI) to examine the structural organization of two auditory cortical regions, Heschl's gyrus (HG) and the planum temporale (PT), in deaf and hearing subjects. The results show preservation of cortical volume in HG and PT of deaf subjects deprived of auditory input since birth. Measurements of grey and white matter, as well as the location and extent of these regions in the deaf showed complete overlap both with matched controls and with previous samples of hearing subjects. The results of the manual volume measures were supported by findings from voxel-based morphometry analyses that showed increased grey-matter density in the left motor hand area of the deaf, but no differences between the groups in any auditory cortical region. This increased cortical density in motor cortex may be related to more active use of the dominant hand in signed languages. Most importantly, expected interhemispheric asymmetries in HG and PT thought to be related to auditory language processing were preserved in these deaf subjects. These findings suggest a strong genetic component in the development and maintenance of auditory cortical asymmetries that does not depend on auditory language experience. Preservation of cortical volume in the deaf suggests plasticity in the input and output of auditory cortex that could include language-specific or more general-purpose information from other sensory modalities.

Adult↗
PubMed2003

A meta-analysis of structural and functional brain imaging in dementia of the Alzheimer's type: a neuroimaging profile.

We conducted a quantitative review of the imaging literature using meta-analytic methodology to characterize further the magnitude of hippocampal deficit in probable Alzheimer's disease (AD) and to determine whether other neuroanatomic structures in AD can better discriminate the disease from normal aging. Additionally, we parceled the discriminability of neuroanatomic structures by duration of disease to determine those structures most sensitive to AD in its early and late stages. One hundred twenty-one studies published between 1984 and 2000 met criteria for inclusion in the present analysis. In total, structural (i.e., CT and MRI) and functional (i.e., SPECT and PET) neuroimaging results from 3511 patients with AD, and 1632 normal healthy controls were recorded across meta-analyses. Our results include neuroimaging profiles for both early onset and longer duration patients with AD. In sum, these profiles yield a signature of diagnostic markers in both cortical and subcortical neuroanatomic areas. This signature is consistent with the clinical phenomenology of Alzheimer's dementia and should aid in the positive identification of AD.

Aged↗
PubMed2002

Brain development and the onset of mood disorders.

Research in mood disorder pathophysiology has stimulated considerable interest in clinical and biologic aspects of mood disorders among children and adolescents. From the clinical perspective, developmental aspects of psychiatric disorders have crystallized in the relatively new theoretical school known as developmental psychopathology. This school attempts to understand the nature of developmental changes in behavior, with the goal of differentiating normal from abnormal stage-related behavior. This perspective has exerted major impact on conceptualizations of psychiatric disorders. From the basic science perspective, biologic findings in emotion have stimulated an integration of basic and clinical approaches to mood disorders. The term emotion is often used to refer to brain states elicited by stimuli for which an organism will extend effort to obtain (rewards) or avoid (punishments). Imaging studies suggest that brain regions engaged by rewarding and punishing stimuli in lower mammals are also implicated in mood disorders. Other studies suggest that environmental factors exert profound effects on the development of these brain regions. The impact of 4 areas of research on our understanding of depression pathophysiology is reviewed: (1) mood disorder onset, (2) structural magnetic resonance imaging (MRI), (3) behavioral or cognitive correlates of major depression, and (4) functional MRI of brain regions engaged across development. This is a US government work. There are no restrictions on its use.

Adolescent↗
PubMed2002

The carpal detachment injury of the triangular fibrocartilage complex.

Triangular fibrocartilage complex (TFCC) injuries were suspected clinically in 22 wrists of 21 patients, but arthrography and MRI assessments of this structure were normal. As conservative therapy for 2 months did not improve their symptoms, wrist arthroscopy was then performed. Although no abnormalities of the TFCC and ligaments were observed, meniscus homologue-like tissue which arose from TFCC was riding on the articular surface of the triquetrum. After resection of this soft tissue with a shaver and a punch, the symptoms disappeared in all cases. The arthroscopic findings suggested that a portion of TFCC that was originally attached to the ulnar side of the triquetrum had become detached.

Adolescent↗