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At least 613 records · Page 34Linked to original sources
PubMed1995

Glutaric acidemia type II: neuroimaging and spectroscopy evidence for developmental encephalomyopathy.

Glutaric acidemia type II is associated with neonatal hypoketotic hypoglycemia, metabolic acidosis, profound hypotonia, progressive cardiomyopathy, and early death. Deficiency of either electron transfer flavoprotein or electron transport flavoprotein:ubiquinone oxidoreductase leads to intramitochondrial accumulation of metabolites of compounds oxidized by enzymes that transfer electrons to flavoprotein. No detailed results of antemortem neuroimaging or magnetic resonance spectroscopy have been described previously. We investigated a patient with typical neonatal onset glutaric acidemia type II without obvious dysmorphogenesis or renal malformations. Cranial tomographic scan revealed hypoplastic temporal lobes and marked widening of the sylvian fissures ("bat-wing" appearance). Cranial magnetic resonance imaging documented underdeveloped frontal and temporal lobes with delayed myelination and hypoplasia of the corpus callosum. 31P-Magnetic resonance spectroscopy of muscle was grossly abnormal with a very low energy state consistent with mitochondrial dysfunction. 1H-Magnetic resonance spectroscopy of brain revealed elevated intracerebral lactate concentration and abnormally high choline/creatine ratio suggestive of dysmyelination. These findings constitute the first in vivo evidence of a developmental encephalomyopathy in glutaric acidemia type II.

Age of Onset↗
PubMedDate not supplied

3D reconstructions of neurofunctional structures for neuroimaging.

An improved method for computer-aided 3D reconstruction of neuroanatomical structures derived from intracranially fixed human brains is demonstrated. The embedded brains are cut into slices. The sliced surfaces are photographed. The outlines of the neuroanatomical structures are drawn onto transparencies which are scanned. The surfaces of the structures are 3D reconstructed with the triangulation method. The cortical structures of the human brain are complex, resulting in possible ambiguities for triangulation which must be solved interactively. These surface reconstructions allow for 3D visualization of the brain and its components comparable with intravital conditions found in clinical neuroimaging.

Algorithms↗
PubMedDate not supplied

The neuroimaging features of the cardiolipin antibody syndrome.

The purpose of our study was to define the neuroimaging features of the cardiolipin antibody syndrome. Thirty-eight patients with elevated anticardiolipin antibody titers were studied with magnetic resonance imaging or computed tomography or both. Two patients underwent cerebral angiography. All patients had recurrent transient ischemic attacks, amaurosis, or strokes. One patient had normal imaging findings. The remaining patients had a combination of infarction and atrophy. Focal infarcts, the most common finding, were seen in 32 patients. Cerebral atrophy was seen in 26 patients and was the only radiographic finding in 5. Angiography demonstrated dramatic abnormalities in the distal portions of the anterior and posterior circulations, with multiple stenosis and occlusions and extensive pial and transdural collateral networks. The cardiolipin antibody syndrome should be suspected in young patients with transient ischemic attacks or strokes in the absence of the usual risk factors for cerebrovascular disease. The presence of raised anticardiolipin antibody titers or the cardiolipin antibody syndrome in patients with lupus, in those with other connective tissue diseases, and in patients without overt manifestations of an autoimmune disorder should be viewed as a risk factor for future ischemic cerebrovascular events. Further understanding of the precise role of these antibodies in the pathogenesis of vascular thrombosis may lead to a better understanding of the mechanisms underlying certain forms of stroke.

Adolescent↗
PubMedDate not supplied

Neuroimaging studies of schizophrenia.

Neuroimaging studies of schizophrenia have identified abnormalities in neuroanatomy, regional brain metabolism and receptor physiology. Computerized tomographic (CT) studies have demonstrated gross ventricular and sulcal enlargement. These findings are probably nonprogressive, and it is not yet clear whether they are present only in a subgroup of patients; whether they represent a reduction in tissue from a previously normal condition or an abnormality in brain development; and what relationship they have to genetic risk for schizophrenia, clinical features, or longterm prognosis. Magnetic resonance imaging (MRI) studies, which offer higher resolution and greater flexibility in imaging plane, are currently focussing on specific neuroanatomic sites, such as the limbic system, basal ganglia and frontal cortex, implicated by neuropathological or clinical studies in the pathophysiology of schizophrenia. Positron emission tomographic (PET) scanning now enables investigators to study brain metabolism and receptor physiology. Evidence to date suggests that there may be significant abnormalities in the pattern of cerebral glucose utilization as well as in the density of dopamine receptors in patients with schizophrenia. Much future work is needed to determine the sensitivity and specificity of these observations as well as the extent to which they are affected by changes in clinical state, attention and medication exposure.

Brain↗
PubMed2006

[Neuroimaging findings in eclamptic patients still symptomatic after 24 hours: a descriptive study about 19 cases].

OBJECTIVE: To describe the neuroimaging findings in eclamptic patients still symptomatic after 24 hours. PATIENTS AND METHODS: All parturients consecutively admitted over a 12-month period for eclampsia and presenting with neurological disorders (coma, focal neurological abnormalities, and eye sight disturbance) underwent cerebral CT-scan and/or MRI. RESULTS: Nineteen women were studied, and all had abnormal neuroradiological findings. The CT-scan was normal in three cases. Cerebral oedema was the predominant lesion (14 cases). It was localized in the parietal or occipital area (12 cases), paraventricular area (1 case), or was diffuse (1 case). Diffusion weighted MRI was performed in four cases and showed cytotoxic cerebral oedema in one case. There were three cases of cerebral venous thrombosis and two cases of intracerebral haemorrhage. CONCLUSION: Various neuroradiological lesions can be observed in eclamptic patients. A localized cerebral oedema is the most frequent. Diffusion weighted MRI should be systematically done when neurological disorders persist.

Adolescent↗
PubMed2005

Fluent versus nonfluent primary progressive aphasia: a comparison of clinical and functional neuroimaging features.

To better characterize fluent and nonfluent variants of primary progressive aphasia (PPA). Although investigators have recognized both fluent and nonfluent patients with PPA, the clinical and neuroimaging features of these variants have not been fully defined. We present clinical and neuropsychological data on 47 PPA patients comparing the fluent (n=21) and nonfluent (n=26) subjects. We further compared language features with PET/SPECT data available on 39 of these patients. Compared to the nonfluent PPA patients, those with fluent PPA had greater impairment of confrontational naming and loss of single word comprehension. They also exhibited semantic paraphasic errors and loss of single word comprehension. Patients with nonfluent PPA were more likely to be female, were more often dysarthric, and exhibited phonological speech errors in the absence of semantic errors. No significant differences were seen with regard to left hemisphere abnormalities, suggesting that both variants result from mechanisms that overlap frontal, temporal, and parietal regions. Of the language measures, only semantic paraphasias were strongly localized, in this case to the left temporal lobe. Fluent and nonfluent forms of PPA are clinically distinguishable by letter fluency, single word comprehension, object naming, and types of paraphasic errors. Nevertheless, there is a large amount of overlap between dysfunctional anatomic regions associated with these syndromes.

Aged↗
PubMed2026

Large-Scale Neuroimaging and Genetic Analyses of the Human Thalamus in Loneliness.

BACKGROUND: Although loneliness is prevalent and significantly impacts society globally, its neural and genetic bases remain poorly understood. The thalamus, which receives sensory information from the environment, may have a more significant role in social interactions than previously recognized. Here, we integrate neuroimaging and genetic approaches to characterize structural differences within the thalamus associated with loneliness. METHODS: We obtained thalamic nuclei volumes on brain scans from 45,834 individuals (age range: 45-82 years) in the UK Biobank and grouped them into 6 anatomical groups. We investigated effects of loneliness and social isolation using self-reported data. Then, we performed a genome-wide association study (GWAS) analysis on the genetic overlap between thalamic volumes and loneliness. RESULTS: The volumes of the whole thalamus and its medial, lateral, and posterior nuclei are significantly reduced in individuals with loneliness compared with those who do not feel lonely. Loneliness with frequent social contact is associated with smaller volumes, whereas social isolation without loneliness shows no such reduction in thalamus volumes. Leveraging data from GWASs on thalamic volumes (n = 30,114) and loneliness (n = 370,342) in the UK Biobank, we identified shared loci between thalamus structure and loneliness. CONCLUSIONS: Our findings support the emerging view that the thalamus plays important roles in social interactions and in the experience of loneliness.

Genetic architecture↗
PubMed2005

Motivating forces of human actions. Neuroimaging reward and social interaction.

In neuroeconomics, reward and social interaction are central concepts to understand what motivates human behaviour. Both concepts are investigated in humans using neuroimaging methods. In this paper, we provide an overview about these results and discuss their relevance for economic behaviour. For reward it has been shown that a system exists in humans that is involved in predicting rewards and thus guides behaviour, involving a circuit including the striatum, the orbitofrontal cortex and the amygdala. Recent studies on social interaction revealed a mentalizing system representing the mental states of others. A central part of this system is the medial prefrontal cortex, in particular the anterior paracingulate cortex. The reward as well as the mentalizing system is engaged in economic decision-making. We will discuss implications of this study for neuromarketing as well as general implications of these results that may help to provide deeper insights into the motivating forces of human behaviour.

Decision Making↗
PubMed2004

Lateralization of amygdala activation: a systematic review of functional neuroimaging studies.

Functional neuroimaging studies of emotion processing consistently report amygdala activation. Most of these studies observed lateralized amygdala activity, indicative of a clear hemisphere-specific processing difference between the left and right amygdalae. Because individual studies use varying paradigms and are limited by statistical power and sensitivity, it has remained unclear whether the left or the right amygdala is more consistently involved in emotional processing. By combining results across 54 fMRI and PET studies in a metaanalysis, we sought to establish if a common pattern of lateralized amygdala activation exists. Our findings indicate that across studies, the left amygdala is more often activated than the right amygdala, suggesting different roles for the left and right amygdalae in emotional processing. Further analysis showed that this predominant left amygdala activation is not significantly related to stimulus type, task instructions, differential habituation rates of the left and right amygdalae or elaborate processing. The results are discussed in relation to methodological and theoretical issues regarding functional brain asymmetry.

Amygdala↗
PubMed2004

Timing speech: a review of lesion and neuroimaging findings.

Time is a fundamental dimension of behavior and as such underlies the perception and production of speech. This paper reviews patient and neuroimaging studies that investigated brain structures that support temporal aspects of speech. The left-frontal cortex, the basal ganglia, and the cerebellum represent structures that have been implicated repeatedly. A comparison with the structures involved in the timing of non-speech events (e.g., tones, lights, finger movements) suggests both commonalities and differences: while the basal ganglia and the cerebellum contribute to the timing of speech and non-speech events, the contribution of left-frontal cortex seems to be specific to speech or rapidly changing acoustic information. Motivated by these commonalities and differences, this paper presents assumptions about the function of basal ganglia, cerebellum, and cortex in the timing of speech.

Basal Ganglia Diseases↗
PubMed2005

Outcome representations, counterfactual comparisons and the human orbitofrontal cortex: implications for neuroimaging studies of decision-making.

Recent research suggests that the primate orbitofrontal cortex (OFC) is critical for representations of outcomes of actions and their subsequent impact on the control of behavior. In parallel, a recent theory of decision-making called decision affect theory (Mellers, Schwartz, and Ritov, Psychological Science, 1997) emphasizes the role of anticipated affective impact of outcomes in guiding choices, and the effects of comparisons with alternative outcomes (i.e., counterfactual effects). In the context of decision affect theory, we present results from two event-related functional MRI experiments consistent with two hypotheses regarding the role of the human OFC in guiding behavior through outcome representation: (1) counterfactual effects are manifested in the human OFC during expectation of outcomes, such that the anticipated affective impact of outcomes is modulated by the nature of the various possible alternative outcomes; (2) a regional specialization exists in the human prefrontal cortex, such that affective impact of potential negative outcomes of actions is represented mainly by the lateral areas of the OFC, while areas situated progressively more medial and dorsal on the ventral and medial PFC are specifically involved in representing the impact of positively valenced outcomes. We also discuss some of the implications that these hypotheses have for neuroimaging studies of reward processing and decision-making, and for studies of neuropsychiatric disorders in which these processes are thought to be disturbed.

Adult↗
PubMed2004

Reward representations and reward-related learning in the human brain: insights from neuroimaging.

This review outlines recent findings from human neuroimaging concerning the role of a highly interconnected network of brain areas including orbital and medial prefrontal cortex, amygdala, striatum and dopaminergic mid-brain in reward processing. Distinct reward-related functions can be attributed to different components of this network. Orbitofrontal cortex is involved in coding stimulus reward value and in concert with the amygdala and ventral striatum is implicated in representing predicted future reward. Such representations can be used to guide action selection for reward, a process that depends, at least in part, on orbital and medial prefrontal cortex as well as dorsal striatum.

Animals↗
PubMed2006

Is there evidence for neural compensation in attention deficit hyperactivity disorder? A review of the functional neuroimaging literature.

This article reviews evidence for the presence of a compensatory, alternative, neural system and its possible link to associated processing strategies in children and adults with attention deficit hyperactivity disorder (ADHD). The article presents findings on a region by region basis that suggests ADHD should be characterized not only by neural hypo-activity, as it is commonly thought but neural hyperactivity as well, in regions of the brain that may relate to compensatory brain and behavioral functioning. In this context studies from the functional neuroimaging literature are reviewed. We hypothesize that impaired prefrontal (PFC) and anterior cingulate (ACC) cortex function in ADHD reduces the ability to optimally recruit subsidiary brain regions and strategies to perform cognitive tasks. The authors conclude that healthy individuals can recruit brain regions using visual, spatial or verbal rehearsal for tasks as needed. In contrast, individuals with ADHD may be less able to engage higher order executive systems to flexibly recruit brain regions to match given task demands. This may result in greater reliance on neuroanatomy that is associated with visual, spatial, and motoric processing rather than verbal strategies. The authors speculate that this impaired flexibility in recruiting brain regions and associated strategies limits adaptation to new cognitive demands as they present and may require more effortful processing.

Attention Deficit Disorder with Hyperactivity↗
PubMed2006

Neuroimaging findings in infantile GM1 gangliosidosis.

GM1 gangliosidosis is an autosomal recessive glycosphingolipid storage disease caused by defects in the enzyme beta-galactosidase. Three clinical forms (infantile-, juvenile-, and adult-onset) of the disease are recognized. Patients with infantile GM1 gangliosidosis present at birth or shortly thereafter with somatic and bony changes, followed by severe neurological deterioration ultimately leading to death within the first 2 years of life. We present the brain CT, MRI and MR spectroscopy (MRS) findings in a 17-month-old Turkish girl with infantile GM1 gangliosidosis. Neuroimaging findings in patients with infantile GM1 gangliosidosis have been reported only in a few cases. In this study, MRS of the thalamus was performed to study the metabolic changes in GM1 gangliosidosis. We showed a a decreased NAA/Cr ration and an increased Cho/Cr ratio. To our knowledge, this is the first report of magnetic resonance spectroscopy findings in type-1 GM1 gangliosidosis.

Aspartic Acid↗
PubMed2005

PET neuroimaging of [11C]mirtazapine enantiomers in pigs.

Previously, we used positron emission tomography (PET) for studying the pharmacokinetics of rac-[11C]mirtazapine in living brain. Our findings showed that rac-[11C]mirtazapine has suitable properties for PET neuroimaging. However, separate studies of enantiomers are typically required for characterizing the pharmacokinetics of a racemic drug. Therefore, we have determined the whole-body distribution and brain pharmacokinetics of S- and R-[11C]mirtazapine in pigs. The enantiomers of [11C]mirtazapine produced similar effective doses of radioactivity in most body organs, except for the brain, in which the dose was approximately 40% higher after injection of S-[11C]mirtazapine than the antipode. Kinetic analyses of dynamic brain PET recordings showed that values for regional accumulation of compound (k3) were significantly higher for S-[11C]mirtazapine than for the antipode, while the values for clearance of compounds from tissue to circulation (k2) were consistently lower for S-[11C]mirtazapine than for the R-form. No reliable difference occurred in the rate of metabolism of S- and R-[11C]mirtazapine in the bloodstream of the pigs. The present findings indicate that enantioselective processes affect the cerebral pharmacokinetics of rac-mirtazapine.

Animals↗
PubMed2006

Early detection of Alzheimer's disease using neuroimaging.

Neuroimaging is being increasingly used to complement clinical assessments in the early detection of Alzheimer's disease (AD). Structural magnetic resonance imaging (MRI) and metabolic positron emission tomography (FDG-PET) are the most clinically used and promising modalities to detect brain abnormalities in individuals who might be at risk for AD but who have not yet developed symptoms. The knowledge of established risk factors for AD enabled investigators to develop enrichment strategies for longitudinal imaging studies to reduce the sample sizes and study duration. The present review focuses on the results obtained by MRI and FDG-PET studies that examined the preclinical AD stages in several at risk populations: (1) individuals from families with autosomal dominant early-onset AD (FAD), (2) patients with mild cognitive impairment (MCI), particularly in memory, who are at very high risk for declining to AD with an estimated decline rate of 10-30% per year, (3) normal young and middle-age subjects carriers of known susceptibility genes for late-onset AD such as the Apolipoprotein E (ApoE) E4 allele, and (4) as age is the main risk factor for AD, normal elderly individuals followed to the onset of MCI and AD. Overall, these studies show that the use of imaging for the early detection of AD is successful even in the earlier stages of disease when clinical symptoms are not fully expressed and the regional brain damage may be limited.

Alzheimer Disease↗
PubMed2006

A comparison of in vivo and in vitro neuroimaging of 5-HT 1A receptor binding sites in the cat brain.

To validate the cat as a suitable model for positron emission tomography imaging (PET) and to gain further knowledge on the anatomical distribution of the serotonin-1A receptor (5-HT 1A) in the feline brain, we used PET with [18F]MPPF and in vitro autoradiography with [3H]MPPF, [3H]8-OH-DPAT and [3H]paroxetine. PET radioactivity curves with [18F]MPPF were very reproducible in anaesthetized cats, with the highest radioactivity uptakes recorded in the hippocampus, cingulate cortex, septum, infralimbic cortex and raphe nucleus, whereas the lowest were found in the cerebellum. [3H]8-OH-DPAT binding displayed a comparable, albeit lower, regional distribution than with [3H]MPPF. Autoradiography also revealed the presence of 5-HT 1A receptor binding sites in the cortex and in the interpeduncular nucleus, due to its greater sensitivity and spatial resolution compared with PET imaging. The cat constitutes an interesting experimental model for PET imaging, as many physiological concepts have been well established with this animal. Our study also shows the advantages of combining complementary neuroimaging techniques such as in vivo PET imaging and in vitro autoradiography to visualize the distribution of the 5-HT 1A receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2004

Neuroimaging in human immunodeficiency virus infection.

Human immunodeficiency virus (HIV) is associated with central nervous system (CNS) changes that may affect cerebral blood flow (CBF), metabolism, structure, and diffusion. Each of the available neuroimaging techniques offers unique insight into the neural mechanisms underlying HIV, as well as a potential means of monitoring disease progression and treatment response. The purpose of the article is to provide a review of experimental studies evaluating changes related to HIV with imaging techniques, including single-photon emission computed tomography (SPECT), positron emission tomography (PET), volumetric magnetic resonance imaging (MRI), functional MRI (fMRI), magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), and perfusion MRI (pMRI).

AIDS Dementia Complex↗