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PubMed2001

Functional neuroimaging studies of category specificity in object recognition: a critical review and meta-analysis.

Functional neuroimaging studies in which the cortical organization for semantic knowledge has been addressed have revealed interesting dissociations in the recognition of different object categories, such as faces, natural objects, and manufactured objects. The present paper critically reviews these studies and performs a meta-analysis of stereotactic coordinates to determine whether category membership predicts patterns of brain activation across different studies. This meta-analysis revealed that, in the ventral temporal cortex, recognition of manufactured objects activates more medial aspects of the fusiform gyrus, as compared with natural object or face recognition. Face recognition activates more inferior aspects of the ventral temporal cortex, as compared with manufactured object recognition. The recognition task used--viewing, matching, or naming--also predicted brain activation patterns. Specifically, matching tasks recruit more inferior occipital regions than do either naming or viewing tasks, whereas naming tasks recruit more anterior ventral temporal sites than do either viewing or matching tasks. These findings indicate that the cognitive demands of a particular recognition task are as predictive of cortical activation patterns as is category membership.

Brain Mapping↗
PubMed2003

Neuroimaging studies of working memory: a meta-analysis.

We performed meta-analyses on 60 neuroimaging (PET and fMRI) studies of working memory (WM), considering three types of storage material (spatial, verbal, and object), three types of executive function (continuous updating of WM, memory for temporal order, and manipulation of information in WM), and interactions between material and executive function. Analyses of material type showed the expected dorsal-ventral dissociation between spatial and nonspatial storage in the posterior cortex, but not in the frontal cortex. Some support was found for left frontal dominance in verbal WM, but only for tasks with low executive demand. Executive demand increased right lateralization in the frontal cortex for spatial WM. Tasks requiring executive processing generally produce more dorsal frontal activations than do storage-only tasks, but not all executive processes show this pattern. Brodmann's areas (BAs) 6, 8, and 9, in the superior frontal cortex, respond most when WM must be continuously updated and when memory for temporal order must be maintained. Right BAs 10 and 47, in the ventral frontal cortex, respond more frequently with demand for manipulation (including dual-task requirements or mental operations). BA 7, in the posterior parietal cortex, is involved in all types of executive function. Finally, we consider a potential fourth executive function: selective attention to features of a stimulus to be stored in WM, which leads to increased probability of activating the medial prefrontal cortex (BA 32) in storage tasks.

Attention↗
PubMed2005

The structure and dynamics of normal language processing: insights from neuroimaging.

This paper reviews current psycholinguistic and neuroimaging evidence on language processing with particular focus on the relationship between production and comprehension. In the first part, different methods of psycholinguistic research are introduced and examples for psycholinguistic models (production: Levelt et al. 1999; comprehension: Friederici 2002) are sketched. In the second part, the neural correlates of semantic, phonological, and syntactic processing are reviewed. For semantics and phonology there seem to be different fronto-temporal networks which are shared in production and comprehension. The results for the processing of syntactic information are not entirely conclusive. Yet the data reveal that phonological strategies may be used in syntactic tasks. This finding opens the discussion of alternative, phonology-based strategies for language processing. Such strategies are accounted for by dual-route models featuring one direct and one indirect route which often involves phonological processing. This insight leads to some tentative conclusions about remediation strategies in dyslexics with selective (e.g., phonological) deficits.

Brain Mapping↗
PubMed1994

The clinical efficacy of magnetic resonance imaging in neuroimaging.

PURPOSE: To assess the clinical efficacy of magnetic resonance imaging (MRI) for neuroimaging and to provide guidelines for clinical practice. STUDY SELECTION: After a comprehensive literature search, studies of the diagnostic accuracy of MRI alone or compared with other tests and of any impact on therapeutic choices or patient outcomes were reviewed by independent readers, followed by discussion to reach consensus conclusions. DATA EXTRACTION: Of 3125 citations retrieved, 156 studies with original data could be rated according to methodologic criteria for study design. One article contributed grade A quality information about diagnostic accuracy, 28 were graded B or C, and 113 were graded D. One randomized trial and 2 comparison studies contributed grade B or C information about the impact on therapeutic choices. Only 2 studies surveyed health status before and after magnetic resonance scanning. RESULTS: For most abnormalities, the sensitivity of MRI is equal to or better than competing technologies. Magnetic resonance imaging shows greater contrast and detail than computed tomography (CT) but also shows more clinically silent abnormalities or incidental findings. A few studies found a modest impact on therapeutic choices but no impact on quality of life or disability. Costs for MRI are high. Computed tomography is sufficient for initial diagnosis of most mass lesions or intracranial hemorrhages requiring immediate intervention. Magnetic resonance imaging is more accurate in the temporal lobes, posterior fossa, brainstem, and spinal cord. For lumbar radiculopathy, MRI and plain spinal CT are as accurate as post-myelographic CT and are less invasive. The role of magnetic resonance angiography for carotid artery stenosis is being studied. CONCLUSIONS: Although suggestions for appropriate use of MRI in clinical practice can be made, the supporting evidence in published studies is weak. Firm guidelines for appropriate use of MRI should be based on further clinical research using more rigorous methods.

Angiography↗
PubMed1999

Early diagnosis of the frontal variant of frontotemporal dementia: how sensitive are standard neuroimaging and neuropsychologic tests?

OBJECTIVE: To examine the role of structural (magnetic resonance imaging [MRI]) and functional (single photon emission computed tomography [SPECT]) imaging and neuropsychologic evaluation in the early diagnosis of frontal variant frontotemporal dementia (fvFTD). BACKGROUND: Current criteria for FTD stress the need for neuropsychologic and functional neuroimaging abnormalities, yet caregivers report lengthy histories of behavioral change. It is not known when, in the course of the disease, these investigations become abnormal, because few longitudinal studies have been reported. METHOD: Longitudinal study of two patients with serial neuropsychologic evaluation and MRI and HMPAO-SPECT scanning. RESULTS: Both patients, men aged 49 and 50, had major changes in personality, behavior, and social conduct that progressed over 5 to 6 years in a way that conformed to the clinical picture of fvFTD. There was remarkably little abnormality on neuropsychologic testing, and MRI and HMPAO-SPECT findings initially were normal. Over time, however, abnormalities on SPECT, frontal atrophy on MRI, or a neuropsychologic profile more typical of fvFTD developed in both patients. CONCLUSIONS: Standard neuropsychologic tests and conventional brain imaging techniques (MRI and SPECT) may not be sensitive to the early changes in fvFTD that occur in the ventromedial frontal cortex, and better methods of accurate early detection are required. These findings are relevant to the diagnostic criteria for FTD.

Atrophy↗
PubMed1999

MR contrast media in neuroimaging: a critical review of the literature.

BACKGROUND AND PURPOSE: MR contrast media are commonly used but do not have evidence-based guidelines for their application. This investigation seeks to define specific methodological problems in the MR contrast media literature and to suggest guidelines for an improved study design. METHODS: To evaluate the reported clinical efficacy of MR contrast media in neuroimaging, we performed a critical review of the literature. From 728 clinical studies retrieved via MEDLINE, we identified 108 articles that evaluated contrast media efficacy for a minimum of 20 patients per study. The articles were randomly assigned to four readers (a fifth reader reviewed all of the articles) who were blinded to article titles, authors, institutions, and journals of publication. The readers applied objective, well-established methodological criteria to assign each article a rating of A, B, C, or D. RESULTS: One hundred one of 108 articles received a D rating, six received a C rating, and one received a B rating. In general, the Methods sections of the evaluated articles did not contain details that would allow the reader to calculate reliable measures of diagnostic accuracy, such as sensitivity and specificity. Specifically, a common problem was failure to establish and uniformly apply an acceptable standard of reference. In addition, images were not always interpreted independently from the reference standard. Radiologists and clinicians need to determine the applicability of any published study to their own practices. Unfortunately, the studies we reviewed commonly lacked clear descriptions of patient demographics, the spectrum of symptomatology, and the procedure for assembling the study cohort. Finally, small sample sizes with inadequate controls were presented in almost all of the articles. CONCLUSION: Although MR contrast media are widely used and play an essential role in lesion detection and confidence of interpretation, no rigorous studies exist to establish valid sensitivity and specificity estimates for their application. On the basis of this review, we herein describe basic methods to document improvements in technology. Such studies are essential to devise measures of diagnostic accuracy, which can form the basis for further studies that will assess diagnostic and therapeutic impact and, ultimately, patient outcomes.

Cohort Studies↗
PubMed1999

Apolipoprotein E and Alzheimer's disease: a genetic, molecular and neuroimaging review.

Alzheimer's disease (AD) is the most common cause of dementia in the elderly and an increasingly significant health concern in our aging population. In the past 10 years, our understanding of this disease has increased dramatically. While the discovery of three rare genetic mutations that can cause AD has provided much information about the causes and progression of the disease, a great deal of attention has been focused on apolipoprotein (ApoE) because of its involvement in the more common, later onset form of AD. Due to the rapid pace of recent advances, it has not been easy for health care professionals, researchers and the general public to keep abreast of these developments. This paper reviews recent research in ApoE and late-onset AD, emphasizing molecular neuropathological, genetic and neuroimaging findings and highlighting current controversies that remain to be addressed.

Aged↗
PubMed1999

[Neuroimaging in patients with CVD].

The development of the neuroimaging technique has revolutionized clinical neurology. This is also true in the field of stroke. Because of the easy accessibility and little time consuming, the computed tomography (CT) should be applied first to the stroke patient and other examinations should be prepared later to the patient due to the severity and the characteristic of the lesion. These are magnetic resonance imaging (MRI) (including MR angiography. MR spectroscopy, diffusion MRI), cerebral angiography, neurosonography (carotid ultrasound, color flow imaging, transcranial Doppler), single photon emission computed tomography (SPECT) and positron emission tomography (PET), etc. It is a matter of common sense that CT and MRI are now particularly important among laboratory examinations for neurological diseases and these non-invasive techniques will become more important for the elderly stroke patients. Recent study cleared the combination of 3-dimensional computed angiography and neurosonography has an informative value and this is especially important for the elderly patients who are fragile and need rapid and accurate diagnosis.

Angiography↗
PubMed1999

[Neuroimaging in cerebral ischemia].

A critical review about different neuroimaging techniques and its contribution to the field of cerebrovascular diseases is presented. The advances of neuroradiology have revolutionized stroke diagnosis. The inminence use of specific treatment for acute brain ischemia (neuroprotective and thrombolytic drugs) make neurologists become familiar with several imaging techniques that will also change stroke management. Nowadays, computed tomography is the mostly available technique for spanish neurologists in the acute phase, because of that, a suitable knowledge of early CT signs of acute infarction make possible use it in peak condition. Perfusion-and-diffusion-weighted magnetic resonance give such a lot of information for acute stroke, that at the near future, therapeutic decisions will be based on these findings. The role of other functional an angiography techniques is discussed.

Acute Disease↗
PubMed1999

[The contribution of functional neuroimaging to the understanding of schizophrenic psychosis].

Recent work on functional neuroimaging in schizophrenia is reviewed. The contribution of these studies is twofold: first, they help reintroducing some of the psychotic symptoms into the framework of well defined cognitive functions, such as representation of actions; second, they point to the implication of specific neural networks (including in the frontal and parietal lobes) in these dysfunctions.

Diagnostic Imaging↗
PubMedDate not supplied

[Clozapine: neuropsychological and neuroimaging studies].

The purpose of this work is to review the main investigations on the cognitive and cerebral effects of clozapine treatment in schizophrenic patients. We remark the differential effects in respect to other neuroleptics. Memory is the neuropsychological function more widely investigated. Clozapine produces visual memory impairment, but not the verbal memory deficit observed following the classical neuroleptic treatment. The effect of clozapine in the cortico-subcortical circuitry points to a differential effects on frontal lobe functions. It has been observed positive effects in controlled verbal fluency and also in visuoconstructive functions. However, in these studies retest effects are not controlled. There are several magnetic resonance imaging works that found a decrease of caudate nuclei volume, in contrast to the increase observed after treatment with classical neuroleptics. The differential effects on neuropsychological functions may be caused by the differential action of antipsychotics on the fronto-estriatal structures. In the future research it is necessary to perform studies including together neuropsychological and functional neuroimaging data in order to clarify the mechanisms responsible of positive and negative psychopharmacological effects.

Antipsychotic Agents↗
PubMed1999

[Clinical neurophysiology and functional neuroimaging at the Société Française de Neurologie (1948-1998)].

The historical role of the French Neurology in the development of anatomo-clinical method is likely to explain why the first communications on electrophysiology were presented in Paris with some delay, as compared with other european societies where the neurophysiological tradition had been more lively. Though clinical neurophysiology, by essence, addresses the pathophysiology of neurological disorders, it has sometimes missed this target at its very beginning, when it aimed at providing data supposed to have some aetiological specificity, causing distrust among neurologists used to accept aetiological diagnosis only when based on post-mortem anatomical evidence. Thanks to the discovery of computerized tomography this time has been over for 25 years, and no one would question anymore the role of clinical neurophysiology and neuroimaging in Neurology, the former giving access to the timing of sensori-motor and cognitive pocesses and the latter to the localization of brain functions. This article reviews the neurophysiological literature published in the Revue Neurologique from 1948 to 1998.

Diagnostic Imaging↗
PubMedDate not supplied

[Lewy bodies dementia: new data for the understanding of neuroimaging].

INTRODUCTION: The criteria for diagnosis of dementia with Lewy bodies (DLB) do not include neuroimaging, and few reports have been published on this. OBJECTIVE: To report our observations of cerebral CAT and MR studies in 25 patients with probable DLB. PATIENTS AND METHODS: Measurement of the surface of the cerebral lobes and the hippocampal region in two axial sections on CAT and MR and three coronal sections on MR. Our controls were 27 persons with probable Alzheimer's disease and 30 healthy persons of the same age group. RESULTS: The size of the frontal, parietal and temporal lobes in DLB is intermediate between the values found in Alzheimer's disease and those found in asymptomatic persons, but without significant differences from these. Atrophy of the hippocampal region seen in DLB is significant as compared with healthy persons, but not when compared with those with Alzheimer's disease, in whom it was greater still. In the patients in whom DLB was still not an advanced stage, there was no atrophy of the occipital lobes, in spite of other observers having found hypoactivity of these lobes on SPECT and PET. CONCLUSION: In the sample studied, structural imaging techniques were not useful in the diagnosis of DLB.

Aged↗
PubMed2000

[Neuroimaging of frontotemporal dementia].

With the development of neuroimaging, frontal lobe atrophy has been demonstrated with increased frequency, first with structural studies (computed tomography and magnetic resonance imaging), then with functional images (Single photon emission computed tomography and Positron emission tomography).

Dementia↗
PubMed2000

[Neuroimaging features of intraventricular neurocytoma].

We presented the clinicopathological features of 8 cases of intraventricular neurocytoma, which was a rare, benign tumor of neuronal origin and affected young patients. In each case the intraventricular tumor existed near the foramen of Monro and/or body of the lateral ventricle, and was associated with ventricular dilatation. A CT scan demonstrated a well-circumscribed iso- or hyperdense mass with some calcification, intratumoral cysts of various sizes and a heterogeneous enhancement. MRI, which was performed in 4 cases, confirmed a mass of isointense or slightly hyperintense on T 1-weighted images, and with multiple sites of attachment (mainly to the septum pellucidum and the head of the caudate nucleus). While these neuroimaging features are helpful in eliminating alternative diagnosis such as ependymomas, choroid plexus papillomas, subependymal giant cell astrocytomas and meningiomas, age of the patient and the tumor location within the lateral ventricle are important features for differential diagnosis.

Adult↗
PubMed1999

[Stereotypes, developmental disorders and neuroimaging studies].

INTRODUCTION: We believe that it is of great interest, in neuropediatric clinic, to value the molar behavior disorders and to accomplish the corresponding molecular alterations in the central nervous system. PATIENTS AND METHODS: We studied 26 patients diagnosed of serious disorders of the development, that were presenting a typical clinic with manual stereotypes. We choose at random 5 children to practice them a study of metabolic neuroimaging through the Positron Emission Tomography with 18Fluoro-Deoxi-Glucose (PET-FDG). RESULTS AND CONCLUSIONS: The conclusion, more meaningful, is that the children with serious disorders of the development present a mature failure in the neuro-function circuits of the thalamus, as well as the cortical connection and association areas. This clinical situation is reinforced by the results of the PET-FDG, that presents a characteristic metabolic image of the autism children, with a bilateral decrease of the capitation of FDG, mainly in regions as thalamus, frontal and temporary lobes.

Adolescent↗
PubMedDate not supplied

[Neuroimaging in epilepsy. Advances in SPECT and PET in epilepsy].

INTRODUCTION: The incorporation of neuroimaging techniques into the protocol for localization of epileptogenous foci has considerably reduced the need for use of intracranial electrodes. DEVELOPMENT: SPECT and PET are most useful in cases of epilepsy with no cerebral morphological anomalies, in which there are therefore no changes which shown on MR. Cerebral SPECT with perfused tracers, such as 99mTc-HMPAO, 123I-MP or 99mTc-ECD, permit the study of patients during interictal and perictal phases. In the latter case, although the procedure is complex, one may observe an increase in cerebral blood flow in the epileptogenous focus in 90% of the patients. PET with FDG allows interictal study of patients, and shows reduced metabolism in the epileptogenic region. By comparison with video-EEG there are S = 84% and SP = 86% in temporal lobe epilepsy. The diagnostic efficiency of these two techniques is rather less in the localization of extratemporal foci and in multifocal epilepsies, although it is always better than with other diagnostic techniques. They have also been shown to be useful in the prognosis of functional recovery after surgery. CONCLUSION: The possibility of studying neuroreceptors may be of great use in the investigation of the etiopathogenesis of epilepsy, and thus lead to improvement in the clinical and therapeutic management of patients. With SPECT, 123I-Iomacenil and 123I-lododexetimide are used. With PET and 11C-Carfentanyl opiate receptors have been studied. With 11C-Fluomacenil one may study the cerebral distribution of the benzodiazepine receptors.

Brain↗