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Results for “BRAIN PHYSIOLOGY”

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At least 19 recordsLinked to original sources
PubMed2006

Quantitative analysis of the effects of physiologic brain motion on point-resolved spectroscopy.

BACKGROUND AND PURPOSE: Although single-voxel proton MR spectroscopy is a noninvasive method that enables measurement of brain metabolite concentrations, it has been shown that physiologic brain motion causes inaccuracies in measurement of metabolite concentrations and increases the overall SD of the measurements when the stimulated echo acquisition mode (STEAM) is used. We tested the hypothesis that the point-resolved spectroscopy (PRESS) technique is less sensitive to physiologic brain motion than the STEAM technique. METHODS: In 10 healthy subjects, spectra were obtained from a voxel located in the left basal ganglia by using the PRESS sequence with cardiac gating and without water suppression to assess global phase change as a function of physiologic brain motion. This was accomplished by acquiring data at various time delays from the R wave throughout the cardiac cycle. Subsequently, spectra were obtained in 10 healthy subjects by using PRESS both without and with cardiac gating, and with water suppression, to determine whether brain motion resulted in a statistically significant difference in mean and SD of measured metabolite concentration. RESULTS: At various time delays from the R wave throughout the cardiac cycle, no significant global phase difference was noted in water signal intensity. In addition, when PRESS data were obtained both without and with cardiac gating (by using an optimal delay obtained from previously published data by using STEAM), no significant difference was seen in measured metabolite concentrations and SDs. CONCLUSION: The PRESS technique is relatively insensitive to physiologic brain motion.

Adult↗
PubMed2004

Modulation of physiological brain hyperthermia by environmental temperature and impaired blood outflow in rats.

To study the role of ambient temperature and brain blood outflow in modulating physiological brain hyperthermia, temperatures in two brain structures (nucleus accumbens or NAcc and hippocampus or Hippo) and a non-locomotor head muscle (musculus temporalis) were monitored in rats exposed to three arousing stimuli (placement in the cage or environmental change, 3-min social interaction with a female rat, 3-min innocuous tail-pinch) under three conditions (intact animals at 23 degrees C or control, intact animals at 29 degrees C, animals with chronically occluded jugular veins at 23 degrees C). While each stimulus in each condition induced hyperthermia, with more rapid and stronger changes in brain structures than muscle, there were significant differences between conditions. At 29 degrees C, animal placement in the cage resulted in stronger temperature increase and larger brain-muscle differentials, while basal temperatures in Hippo and muscle (but not in NAcc) were higher than control. At 29 degrees C, hyperthermia during social interaction was smaller but more prolonged, while the response to tail-pinch was similar to that seen at normal environmental temperatures. Animals with chronically occluded jugular veins had similar basal temperatures but showed much weaker hyperthermia than intact animals during each stimulus presentation; temperature increases in brain structures, however, were much stronger than in the muscle. Our data suggest that the brain is able to decrease neural activation induced by environmental challenges under conditions of impaired blood outflow and restricted heat dissipation to the external environment.

Analysis of Variance↗
PubMed1980

The "milieu interieur"-a model of brain physiology and pathophysiology.

The "milieu interieur" or "internal environment" of the brain is determined by the glial cells, the cerebrospinal fluid, the blood-brain barrier, the cerebral blood flow, the central regulation of respiration, and the intracranial pressure. Anaesthetic agents and anoxia-ischaemic insult can disrupt this important but vulnerable neuronal environment. Head injury is used as an example of a common insult to the neuronal environment and the principles of management are discussed, using a model of brain physiology and pathophysiology which can be modified to include other clinical situations.

Anesthetics↗
PubMed1996

Effect of stepped hypoglycemia on regional cerebral blood flow response to physiological brain activation.

The effect of vasoactive stimuli on cerebral blood flow (CBF) has been variously reported as normal or impaired by hypoglycemia. We measured regional CBF (rCBF) in contralateral somato-sensory cortex at rest and during vibrotactile stimulation of one hand in four normal awake human volunteers during fasting euglycemia (5.1-5.2 mumol/ml) with 0.9% saline infusion, euglycemia (5.1-5.2 mumol/ml) with hyperinsulinemic clamp, mild hypoglycemia (3.2-3.6 mumol/ml) with hyperinsulinemic clamp, and moderate hypoglycemia (2.3-3.2 mumol/ml) with hyperinsulinemic clamp. No changes in mean arterial pressure, arterial PCO2, or arterial oxygen content occurred. There was no change in the magnitude of the normalized rCBF response to physiological brain stimulation with progressive arterial hypoglycemia (r = 0.10, P = 0.73). We interpret this to mean that there was a progressive reduction in cerebral glucose delivery to the area of physiological activation as arterial glucose concentrations fell. Therefore, the increase in rCBF during physiological brain activation is not regulated by a mechanism that matches local cerebral glucose supply to local cerebral glucose demand.

Adult↗
PubMed1997

Chronic microelectrode investigations of normal human brain physiology using a hybrid depth electrode.

Neurosurgeons have unique access to in vivo human brain tissue, and in the course of clinical treatment important scientific advances have been made that further our understanding of normal brain physiology. In the modern era, microelectrode recordings have been used to systematically investigate the cellular properties of lateral temporal cerebral cortex. The current report describes a hybrid depth electrode (HDE) recording technique that was developed to enable neurosurgeons to simultaneously investigate normal cellular physiology during chronic intracranial EEG recordings. The HDE combines microelectrode and EEG recordings sites on a single shaft. Multiple microelectrode recordings are obtained from MRI defined brain sites and single-unit activity is discriminated from these data. To date, over 60 HDEs have been placed in 20 epilepsy surgery patients. Unique physiologic data have been gathered from neurons in numerous brain regions, including amygdala, hippocampus, frontal lobe, insula and Heschl's gyrus. Functional activation studies were carried out without risking patient safety or comfort.

Action Potentials↗
PubMed1987

A relationship between anatomical and physiological brain pathology in schizophrenia: lateral cerebral ventricular size predicts cortical blood flow.

The authors studied the relationship between lateral cerebral ventricular size and regional cerebral blood flow during mental activation in 30 patients with schizophrenia. Patients with large ventricles had diffusely lower cortical gray matter blood flow than patients with small ventricles. In addition, an inverse correlation between ventricular size and prefrontal blood flow was observed while patients were attempting to solve a neuropsychological test specifically related to the prefrontal cortex. These data suggest that structural brain pathology impairs prefrontal physiology in schizophrenia, implicating a neural mechanism for the intellectual deficits characteristic of this disorder.

Adolescent↗
PubMed2002

Effects of euthanasia on brain physiological activities monitored in real-time.

Animal experimentation is terminated by the euthanasia procedure in order to avoid pain and minimize suffering. Very little is known about the real time physiological changes taking place in the brain of animals during the euthanasia. Since there is no way to evaluate the suffering of animals under euthanasia, it is assumed that objective physiological changes taking place could serve as a good way to compare various types of euthanasia procedures. In the present study we compared the effect of euthanasia induced by i. v. injection of concentrated KCL to that of Taxan T-61 (a standard mixture used by veterinarians). The responses of the cat brain were evaluated by monitoring the hemodynamic (CBF), metabolic (NADH redox state), electrical (EcoG) and extracellular ion levels, as an indicator to the ionic homeostasis.

Amides↗
PubMed2006

The brain as a system of nested but partially overlapping networks. Heuristic relevance of the model for brain physiology and pathology.

A new model of the brain organization is proposed. The model is based on the assumption that a global molecular network enmeshes the entire central nervous system. Thus, brain extra-cellular and intra-cellular molecular networks are proposed to communicate at the level of special plasma membrane regions (e.g., the lipid rafts) where horizontal molecular networks can represent input/output regions allowing the cell to have informational exchanges with the extracellular environment. Furthermore, some "pervasive signals" such as field potentials, pressure waves and thermal gradients that affect large parts of the brain cellular and molecular networks are discussed. Finally, at least two learning paradigms are analyzed taking into account the possible role of Volume Transmission: the so-called model of "temporal difference learning" and the "Turing B-unorganised machine". The relevance of this new view of brain organization for a deeper understanding of some neurophysiological and neuropathological aspects of its function is briefly discussed.

Animals↗