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At least 847 records · Page 47Linked to original sources
PubMed2002

The neural basis of functional brain imaging signals.

The haemodynamic responses to neural activity that underlie the blood-oxygen-level-dependent (BOLD) signal used in functional magnetic resonance imaging (fMRI) of the brain are often assumed to be driven by energy use, particularly in presynaptic terminals or glia. However, recent work has suggested that most brain energy is used to power postsynaptic currents and action potentials rather than presynaptic or glial activity and, furthermore, that haemodynamic responses are driven by neurotransmitter-related signalling and not directly by the local energy needs of the brain. A firm understanding of the BOLD response will require investigation to be focussed on the neural signalling mechanisms controlling blood flow rather than on the locus of energy use.

Action Potentials↗
PubMed1999

Alzheimer's disease: seeking new ways to preserve brain function. Interview by Alice V. Luddington.

Alzheimer's disease (AD) is characterized in the brain by the deposition of amyloid protein outside the neuron, resulting in the formation of plaques, and inside the neuron with neurofibrillary tangles. It is not yet known what causes these pathologic changes, although age and genetics are major risk factors. The cholinesterase inhibitors tacrine and donepezil block acetylcholinesterase and therefore preserve the neurotransmitter acetylcholine. Three other investigational cholinesterase inhibitors are rivastigmine, metrifonate, and galanthamine. Existing therapies being studied for use in AD include vitamin E, estrogen preparations, and anti-inflammatory agents. The physician's role is to care for both the AD patient and the family, which are profoundly affected by this disease.

Alzheimer Disease↗
PubMed1987

[Some new biochemical knowledge on the effect of nutritional factors on brain function].

A survey is given of the importance of the sufficient supply of the brain with amino acids, with glucose, fatty substances (in particular with linoleic acid), with vitamins (A, E, B1, B2, B6, nicotinamide, choline, B12), with mineral substances and with trace elements (in particular with Fe, Zn, and Cu), taking into particular consideration findings of animal experiments. The transport capacity for the transfer of the substrates and essential nutritional factors into the nerve cells is different. In a high activity the formation of noradrenaline, of acetyl choline and of serotonin is in certain nerve cells influenced by the size of the uptake of the molecules necessary for this. By a protein-rich nutrition the formation of the noradrenaline and acetyl choline which are important for the maintenance of the waking state, by a carbohydrate-rich diet the formation of the serotonin which is among others important for the evocation of sleep are furthered.

Amino Acids↗
PubMed1981

Effects of precursors on brain neurotransmitter synthesis and brain functions.

This paper reviews factors which influence the levels of aminergic transmitters in the brain. In particular precursor availability to the brain influences the rates of synthesis of serotonin, the catecholamines, and acetylcholine by brain neurons. The diet readily influences brain neurotransmitter formation via this mechanism. At present, the importance of this relationship to body regulation is not well understood. Nonetheless, precursors (tryptophan, tyrosine, choline, and lecithin) have begun to find uses as therapeutic agents in the treatment of disease states involving diminished transmitter formation and release. Hopefully, these compounds will find a wide range of uses, as they lack many of the side effects that accompany the use of drugs.

Acetylcholine↗
PubMed2002

Maturation of brain function associated with response inhibition.

OBJECTIVE: To investigate the developmental trajectory of response inhibition and, more specifically, whether there is a dissociation of function in the prefrontal cortex over the course of development of executive function and associated response inhibition abilities. METHOD: Nineteen typically developing subjects, ranging in age from 8 to 20, performed a Go/NoGo task while behavioral and functional magnetic resonance imaging (fMRI) data were collected. RESULTS: All subjects performed the task with few errors of omission and commission. No relationship between accuracy and age emerged, but the ability to inhibit responses significantly improved with age. Analyses of fMRI data revealed a positive correlation between activation and age in the left inferior frontal gyrus/insula/orbitofrontal gyrus, and a negative correlation between activation and age in the left middle/superior frontal gyri. CONCLUSION: These data provide the first evidence of dissociable processes occurring in the prefrontal cortex during development of executive functions associated with response inhibition: (1) Younger subjects activate more extensively than older subjects in discrete regions of the prefrontal cortex, presumably due to increased demands and inefficient recruitment of brain regions subserving executive functions including working memory. (2) Older subjects show increasingly focal activation in specific regions thought to play a more critical role in response inhibition.

Adolescent↗
PubMed1998

Cerebral networks and functional brain asymmetry: evidence from regional metabolic changes during word repetition.

Word repetition causes a significant bilateral metabolic increase in both superior temporal cortices. Frontal speech areas are less activated despite their presumable speech competence. We investigated in this study the relationship between frontal and temporal cortical areas during word repetition. We measured regional cerebral metabolic rates of glucose (CMRGI) in 15 normal subjects with positron emission tomography (PET) at rest and during word repetition. Significant correlations connected frontal and temporal areas of both hemispheres, notwithstanding their different levels of mean metabolic activation. The left planum temporale was a hub of significant interregional correlations, in contrast to its contralateral mate. This study indicates that an asymmetric network of significant connections orchestrates the speech-relevant cortical areas according to the actual needs of speech processing.

Adult↗
PubMedDate not supplied

[The effect of a high-intensity radiation exposure on the brain function of monkeys. The postradiation changes in the EEG response to rhythmic photostimulation].

In experiments with monkeys (Macaca fascicularis) it has been shown that whole-body irradiation with a dose of 45 Gy (6.5 Gy/s) causes considerable changes in the EEG response to rhythmic photostimulation (PS). These changes are: reduction of the desynchronizing effect of PS with regard to a background rhythmicity; decrease in the reception rate of the rhythms of light flashes (RLF); narrowing of the RLF frequency range; and increase in the reaction momentum. The postirradiation changes in the EEG response to PS are considered as a manifestation of inhibition of the cortex functional activity and impairment of sensory information processing in the brain.

Animals↗
PubMedDate not supplied

[Brain function in patients with atherosclerotic circulatory encephalopathy].

Based on the analysis of findings from clinical and paraclinical investigations (ultrasonic vascular diagnosis, electroencephalography, computerized tomography, angiography) in 244 patients with atherosclerotic dyscirculatory encephalopathy, functional status was studied as were structural alterations in the brain tissue in stenosing lesions of precerebral arteries. The first clinical manifestations of atherosclerotic dyscirculatory encephalopathy in the presence of damage to the vestibular-basilar system were found to be dysfunction of column structures of vestibular apparatus, reticular formation and posterior longitudinal fascicle, and, in the presence of damage to the carotid area, -- dysfunction of cortex of frontal, parietal and temporal lobes of the brain.

Adult↗
PubMed2000

[Deep brain stimulation therapy: control of human brain function by chronically implanted electrodes].

During the last decade, it has become increasingly clear that deep brain stimulation(DBS) is useful for controlling various neurological disorders, including intractable pain and involuntary movements. The development of an implantable and programmable pulse-generator has greatly facilitated the clinical application of DBS therapy. The history and clinical data of DBS therapy currently available from the literature, together with our own cases treated by DBS, are reviewed. DBS therapy has many advantages over conventional neuroablative therapies, including reversibility of the procedure, controllability and relative selectivity of the effects, and possible plastic effects on neural function. Further evolution of the stimulation system, such as through integration with neuromonitoring devices, would open up a new field of restorative neurology and neurosurgery.

Brain↗
PubMed1989

[Brain structure and brain function in anorexia nervosa: a computerized tomography study].

Cranial computed tomography (CT) was performed in 12 patients with anorexia nervosa revealing that the majority of the patients displayed ventricular dilatation and/or sulcal widening. In six patients re-examined these structural brain alterations showed a strong trendency towards normalization after weight gain. With the intention of finding a functional correlate of the CT abnormalities, the regional cerebral blood flow (rCBF) was measured at admission and once again after weight gain and compared with the flow rates of a healthy control group. The mean flow rates assessed at the first examination did not significantly differ from those assessed at the second examination and from those of a control group. Thus, despite the CT findings of structural brain abnormalities, the measurement of the regional cerebral blood flow gave no hint of a reduced functioning of certain brain areas in anorexia nervosa.

Adolescent↗
PubMed2002

Application of sensitivity-encoded echo-planar imaging for blood oxygen level-dependent functional brain imaging.

The benefits of sensitivity-encoded (SENSE) echo-planar imaging (EPI) for functional MRI (fMRI) based on blood oxygen level-dependent (BOLD) contrast were quantitatively investigated at 1.5 T. For experiments with 3.4 x 3.4 x 4.0 mm(3) resolution, SENSE allowed the single-shot EPI image acquisition duration to be shortened from 24.1 to 12.4 ms, resulting in a reduced sensitivity to geometric distortions and T(*)(2) blurring. Finger-tapping fMRI experiments, performed on eight normal volunteers, showed an overall 18% loss in t-score in the activated area, which was substantially smaller than expected based on the image signal-to-noise ratio (SNR) and g-factor, but similar to the loss predicted by a model that takes physiologic noise into account.

Brain↗