SEARCH · PubMed Health

Results for “brain function”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources

PubMed1999

Exploring brain function with magnetic resonance imaging.

Since its invention in the early 1990s, functional magnetic resonance imaging (fMRI) has rapidly assumed a leading role among the techniques used to localize brain activity. The spatial and temporal resolution provided by state-of-the-art MR technology and its non-invasive character, which allows multiple studies of the same subject, are some of the main advantages of fMRI over the other functional neuroimaging modalities that are based on changes in blood flow and cortical metabolism. This paper describes the basic principles and methodology of fMRI and some aspects of its application to functional activation studies. Attention is focused on the physiology of the blood oxygenation level-dependent (BOLD) contrast mechanism and on the acquisition of functional time-series with echo planar imaging (EPI). We also provide an introduction to the current strategies for the correction of signal artefacts and other image processing techniques. In order to convey an idea of the numerous applications of fMRI, we will review some of the recent results in the fields of cognitive and sensorimotor psychology and physiology.

Artifacts↗

PubMed1999

Structural and functional brain changes in bipolar disorder: a selective review.

The purpose of this paper is to provide a concise, selective review of the major issues and findings germane to structural and functional neuroimaging studies of bipolar affective disorder (BPD). In attempting to identify the brain changes associated with BPD, investigators have used neuroimaging techniques to focus on several interrelated questions. These are: What are the changes and where do they occur? Do their nature and location suggest a particular etiopathologic basis or have notable clinical correlates? With regard to specificity, are the changes unique to BPD, or do they overlap with those reported in other neuropsychiatric illnesses, especially schizophrenia? Do they occur in brain systems that normally play a role in modulating mood? Finally, how do the brain changes integrate with neurocognitive, neurogenetic, and neuropathologic data in the same patients? To date, these questions have been addressed only preliminarily. We outline some of the strategies used to pursue answers to these questions and review conclusions to date.

Affective Symptoms↗

PubMed1999

Brain function in the elderly: role of vitamin B12 and folate.

Vitamin B12 (cobalamin) deficiency associated neuropathy, originally called subacute combined degeneration, is particularly common in the elderly. The potential danger today is that with supplementation with folic acid of dietary staples such as flour, that the incidence of this disease could rise as folic acid, as opposed to natural folate (N5CH3HFGlu1), enters the cell and the metabolic cycle by a cobalamin independent pathway. This chapter briefly describes the clinical presentation of the disease, which unless treated will induce permanent CNS damage. The biochemical basis of the interrelationship between folate and cobalamin is the maintenance of two functions, nucleic acid synthesis and the methylation reactions. The latter is particularly important in the brain and relies especially on maintaining the concentration of S-adenosylmethionine (SAM) which, in turn, maintains the methylation reactions whose inhibition is considered to cause cobalamin deficiency associated neuropathy. SAM mediated methylation reactions are inhibited by its product S-adenosylhomocysteine (SAH). This occurs when cobalamin is deficient and, as a result, methionine synthase is inhibited causing a rise of both homocysteine and SAH. Other potential pathogenic processes related to the toxic effects of homocysteine are direct damage to the vascular endothelium and inhibition of N-methyl-D-aspartate receptors.

Aged↗

PubMed2001

Validation of a 3D reconstruction algorithm for EIT of human brain function in a realistic head-shaped tank.

Previous work has demonstrated that electrical impedance tomography can be used to image human brain activity during evoked responses, but two-thirds of the reconstructed images fail to localize an impedance change to the expected stimulated cortical area. The localization failure may be caused by modelling the head as a homogenous sphere in the reconstruction algorithm. This assumption may lead to errors when used to reconstruct data obtained from the human head. In this study a 3D reconstruction algorithm, based on a model of the head as a homogenous sphere, was characterized by simulating the algorithm model, the head shape and the presence of the skull in saline-filled tanks. EIT images of a sponge, 14 cm3 volume with a resistivity contrast of 12%, were acquired in three different positions in tanks filled with 0.2% saline. In a hemispherical tank, 19 cm in diameter, the sponge was localized to within 3.4-10.7% of the tank diameter. In a head-shaped tank, the errors were between 3.1 and 13.3% without a skull and between 10.3 and 18.7% when a real human skull was present. A significant increase in localization error therefore occurs if an algorithm based on a homogeneous sphere is used on data acquired from a head-shaped tank. The increased error is due to the presence of the skull, as no significant increase in error occurred if a head-shaped tank was used without the skull present, compared to the localization error within the hemispherical tank. The error due to the skull significantly shifted the impedance change within the skull towards the centre of the image. Although the increased localization error due to the skull is not sufficient to explain the localization errors of up to 50% of the image diameter present in the images of some human subjects, the future use of a realistic head model in the reconstruction algorithm is likely to reduce the localization error in the human images due to the presence of the skull.

Algorithms↗

PubMed1990

[A simplified method for evaluation of brain function--basic and clinical study on electroencephalogram by the nasopharyngeal lead].

In making a decision for death, it is well said that brain stem electroencephalogram (EEG) could be an important index. We applied Ishida's nasopharyngeal lead to animals (canine), normal healthy men and patients with brain dysfunction. In normal healthy men, the nasopharyngeal lead revealed clear brain waves. Additionally, we tried a photic stimulation in all the models and a gradual removal of the cerebrum in canines to investigate whether interaction between Ishida's nasopharyngeal lead and the cortical electroencephalogram exists. Furthermore, whenever there was a chance, we examined instances with brain dysfunction by the method, and confirmed that brain waves obtained from Ishida's nasopharyngeal lead were derived from the skull base.

Adult↗

PubMed2006

Speech apraxia without oral apraxia: can normal brain function explain the physiopathology?

Apraxia of speech, usually associated with stroke, refers to the inability to perform speech motor movements typically with an intact ability to execute non-speech oral movements. It is uncertain whether apraxia of speech results from damage affecting the insula or the inferior frontal gyrus. The controversy started because of conflicting results from studies investigating patients with disrupted brain structure, when dysfunction of both sites can coexist. We conducted a functional magnetic resonance imaging study of individuals without neurological disorders comparing speech and non-speech movements. Speech movements did not recruit the insula, but activated the left inferior frontal gyrus, suggesting that Broca's area, but not the insula, is critical for speech articulation.

Adolescent↗

PubMedDate not supplied