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Results for “brain function”

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At least 1,315 records · Page 73Linked to original sources

PubMed1996

Prospective associations between lateralised brain function and immune status in HIV infection: analysis of EEG, cognition and mood over 30 months.

Prospective relations between individual differences in both lateralised neuro-psychophysiological functions and mood ratings with immune status (CD4 and CD8 counts) were examined in asymptomatic HIV-positive men (n = 27) over thirty months. They participated in a controlled study of zidovudine versus placebo (results published elsewhere). Measures included EEG spectra, neuropsychological tests and mood ratings. A model of reciprocal lateralised influences on the immune system was tested whereby patients with left superior to right hemispheric functions were predicted to show a less deleterious outcome than those with the opposite asymmetry pattern. Prospective relations with immune status were found in the EEG with lateralised theta, alpha and beta activity; among cognitive measures with word fluency, semantic processing, and lateralised motor and recognition memory (word/face) processes; with mood ratings including depression, confusion and the total mood score. The nature of the effects supported the laterality predictions. These unique data, showing that neuro-psychophysiological factors in HIV+ but otherwise healthy subjects predict immune competence and compromise present 2-3 years later, warrant replication in a larger cohort.

Adult↗

PubMed2026

The interplay between circadian misalignment or sleep disturbances and cognition and brain function in individuals with different degrees of insulin resistance - a systematic review.

Disruption of sleep increases the risk of type 2 diabetes and worsens cognitive outcomes, yet few studies have evaluated the interaction between insulin resistance and sleep parameters in relation to cognitive outcomes or the risk of dementia. This systematic review examines how circadian misalignment and sleep disturbances affect cognition and neuroimaging findings in individuals with varying degrees of insulin resistance. Across 27 studies, disrupted circadian rhythmicity and sleep disturbances were negatively associated with brain health, possibly through its effects on insulin sensitivity, whereas the impact of sleep duration and quality were inconclusive. Methodological heterogeneity, reliance on cross-sectional designs, and limited control for confounders restricted definitive conclusions and highlighted the need for longitudinal and interventional studies with objective measurements. Nonetheless, the findings support circadian rhythmicity as a potentially modifiable risk factor for preserving cognition in insulin-resistant populations. Future research should prioritise prospective and interventional studies and focus on biological markers rather than self-reported outcomes.

Humans↗

PubMedDate not supplied

Role of cholinergic mechanisms in alterations of rabbit brain functional activity during sea-sickness.

Using the hydrogen-clearance method in chronic experiments on alert rabbits, we investigated the dynamics of changes in local and total cerebral blood-flow, oxygen pressure, bioelectrical activity of the motor, auditory, and visual zones of the cerebral cortex, the heart rate during sea-sickness and the effect of the cholinolytic scopolamine upon changes in these indices. It was found that scopolamine affects the character and direction of changes in both local and overall blood flow in the brain during sea-sickness. Scopolamine does not substantially alter oxygen pressure in the cortical structure of the brain and does not eliminate brachycardia arising during sea-sickness. On the electrocorticogram (ECoG), it does cause an intensification of activational processes and an increase in the total bioelectrical activity, especially in the motor zones of the cerebral cortex. It is suggested that the protective effect of scopolamine during sea-sickness is connected with its central cholinolytic action and with the decrease it brings about in the cerebral hemodynamics and bioelectrical activity of the cerebral cortex arising during "motion sickness."

Animals↗

PubMed2003

[Brain function peculiarities in premature babies and infants with perinatal encephalopathy and cerebral palsy].

Eighty five children with perinatal encephalopathy and cerebral palsy have been studied. EEG analysis showed functional imbalances of cortical and subcortical structures. A delay of cortical electrogenesis development and cortical functional activity were reduced, particularly in its sensomotor areas and left hemisphere with insufficient efferent impulse flow into underlying structures and predominance of electrical subcortical and stem structure activity. The changes discovered may relate directly to psychomotor retardation.

Brain↗

PubMed1984

[Brain function and artificial respiration].

Haemodynamic changes (cerebral perfusion pressure, cerebral blood flow) and variations of blood gases (especially paCO2) induced by mechanical ventilation, can influence cerebral function. The cerebral response to these changes is modified by the individual pathophysiology of the cranial contents. The cerebral mechanisms of adaptation allow a safe ventilation of a patient without cerebral disorders, provided ventilation is within normal clinical limits. In patients, however, whose mechanisms of adaption are impaired locally or globally, the pathophysiological situation may become grossly changed by variations in the ventilatory pattern. A therapeutical application of this interaction is controlled hyperventilation to lower intracranial pressure. On the other hand, changes in the ventilatory pattern (variation of PEEP-level, variation of minute volume, bronchial toilet) can impair cerebral function critically. As the individual reactions cannot be predicted in this group of patients, monitoring of haemodynamic parameters (MAP, CVP, CO), blood gases, intracranial pressure, and EEG is of utmost importance.

Acid-Base Equilibrium↗

PubMed2005

Functional brain imaging of a complex navigation task following one night of total sleep deprivation: a preliminary study.

Several neuroimaging studies have demonstrated compensatory cerebral responses consequent to sleep deprivation (SD), but all have focused on simple tasks with limited behavioral response options. We assessed the cerebral effects associated with SD during the performance of a complex, open-ended, dual-joystick, 3D navigation task (simulated orbital docking) in a cross-over protocol, with counterbalanced orders of normal sleep (NS) and a single night of total SD (approximately 27 h). Behavioral performance on multiple measures was comparable in the two sleep conditions. Functional magnetic resonance imaging revealed multiple compensatory SD > NS cerebral responses, including the posterior superior temporal sulcus [Brodmann area (BA) 39/22/37], prefrontal cortex (BA 9), lateral temporal cortex (BA 22/21), and right substantia nigra. Right posterior cingulate cortex (BA 31) exhibited NS > SD activity. Our findings extend the compensatory cerebral response hypothesis to complex, open-ended tasks.

Adult↗

PubMed2004

Functional brain imaging in the differential diagnosis of Parkinson's disease.

The accurate diagnosis of idiopathic Parkinson's disease (IPD) is not only important for deciding on treatment strategies and providing a prognosis, but also crucial for studies designed to investigate the aetiology and pathogenesis of parkinsonian disorders. Over recent decades, improvements in the characterisation of the parkinsonian syndromes have led to improvements in clinical diagnostic accuracy; however, clinical criteria alone are not always sufficient to distinguish between IPD and other parkinsonian syndromes, particularly in the early stages of disease and in atypical presentations. Therefore, in addition to the development and implementation of diagnostic clinical assessments, there is a need for available objective markers to aid the physician in the differential diagnosis of IPD. Functional neuroimaging holds the promise of improved diagnosis and allows assessment in early disease. In this review, the use of PET and single photon emission CT in the differential diagnosis of IPD are discussed.

Brain Mapping↗

PubMed2004

Acupuncture using laser needles modulates brain function: first evidence from functional transcranial Doppler sonography and functional magnetic resonance imaging.

Acupuncture using laser needles is a new totally painless stimulation method which has been described for the first time. This paper presents an experimental double-blind study in acupuncture research in healthy volunteers using a new optical stimulation method. We investigated 18 healthy volunteers (mean age +/- SD: 25.4 +/- 4.3 years; range: 21-30 years; 11 female, 7 male) in a randomized controlled cross-over trial using functional multidirectional transcranial ultrasound Doppler sonography (fTCD; n = 17) and performed functional magnetic resonance imaging (fMRI) in one volunteer. Stimulation of vision-related acupoints resulted in an increase of mean blood flow velocity in the posterior cerebral artery measured by fTCD [before stimulation (mean +/- SE): 42.2 +/- 2.5; during stimulation: 44.2 +/- 2.6; after stimulation: 42.3 +/- 2.4 cm/s, n.s.]. Mean blood flow velocity in the middle cerebral artery decreased insignificantly. Significant changes (p < 0.05) of brain activity were demonstrated in the occipital and frontal gyrus by fMRI. Optical stimulation using properly adjusted laser needles has the advantage that the stimulation cannot be felt by the patient (painless and no tactile stimulation) and the operator may also be unaware of whether the stimulation system is active. Therefore true double-blind studies in acupuncture research can be performed.

Acupuncture↗

PubMed1991

[Application of quantitative autoradiography to the measurement of brain function activity in rats during post-natal development].

Quantitative autoradiographic techniques for the measurement of local cerebral functional activity have been set up in the rat during postnatal development and applied to the measurement of local cerebral glucose and beta-hydroxybutyrate utilization as well as of local cerebral blood flow from 10 to 35 days after birth. These techniques have shown transient peaks of cerebral activity for both energy metabolism, expressed in terms of glucose plus beta-hydroxybutyrate utilization, and blood flow from 14 to 17 days of postnatal age. These methods which allow the mapping of functional activity simultaneously in all cerebral regions of conscious animals represent a tool of choice for the study of metabolism and blood flow regional changes, particularly in pathological situations.

3-Hydroxybutyric Acid↗

PubMed1990

Effects of prolonged mental work on functional brain topography.

Topographic patterns of event-related covariance between electrodes were measured from subjects performing a difficult memory and fine-motor control task for 10-14 h. Striking changes occurred in the patterns after subjects performed the task for an average of 7-9 h, but before performance deteriorated. Pattern strength was reduced in a fraction-of-a-second-long response preparation interval over midline precentral areas and over the entire left hemisphere. By contrast, pattern strength in a succeeding response inhibition interval was reduced over all areas. The pattern changed least in an intervening interval associated with visual-stimulus processing. This suggests that, in addition to the well-known global reduction in neuroelectric signal strength, functional neural networks are selectively affected by sustained mental work in specific fraction-of-a-second task intervals.

Analysis of Variance↗

PubMed1997

Integration of functional brain mapping in image-guided neurosurgery.

Magnetoencephalographic (MEG) brain mapping was performed in 90 patients with lesions associated with eloquent sensorimotor cortex. The MEG-derived sensorimotor mapping information was utilised for risk analysis and planning. Subsequently, these patients underwent either stereotactic volumetric resection, stereotactic biopsy or non-surgical management of their lesions. In seventeen patients, the MEG sensorimotor localization was integrated into an operative stereotactic database (consisting of CT, MRI and digital angiography) to be used in an interactive fashion during computer-assisted stereotactic volumetric resection procedures. The spatial relationship between the MEG derived functional anatomy, the structural/radiological anatomy and the pathology could then be viewed simultaneously, thereby affording a safer trajectory and approach. In addition, the real-time availability of functional mapping information in an interactive fashion helped reduce surgical risk and minimise functional morbidity. All of these patients had resection of their lesions with no change in their neurological status. In conclusion, MEG is a non-invasive, accurate, and reproducible method for pre-operative assessment of patients with lesions associated with eloquent sensory and motor cortex. The interactive use of MEG functional mapping in the operating room can allow for a safer approach and resection of these eloquent cortex lesions.

Adolescent↗

PubMed1982

Hibernation "trigger": opioid-like inhibitory action on brain function of the monkey.

A hibernation "trigger" factor derived from the blood of the hibernating woodchuck acts to suppress vital physiological processes in the primate. When infused into the cerebral ventricle of the conscious monkey, the factor induced hypothermia, behavioral depression, bradycardia and aphagia. The opiate antagonists, naloxone and naltrexone, either reverse or retard these behavioral and physiological signs. We hypothesize that the "trigger" molecule is an endogenous opioid-like peptide which may be unique to the hibernator. Moreover, the non-hibernating primate apparently possesses receptor sites in the brain that are capable of responding to this potent molecule.

Animals↗

PubMed1981

Gamma-melanotropin and brain function.

In view of the close structural similarity between the pro-opiocortin fragment, gamma-MSH, and ACTH/MSH-type peptides, the behavioural profile of gamma-MSH was explored. Attention was first focused on behavioural procedures in which ACTH/MSH-related neuropeptides have been found effective. It was found that gamma-MSH and ACTH-like neuropeptides had opposite effects on avoidance behaviour. In this respect the activity of gamma-MSH resembles that of opiate antagonists rather than that of beta-endorphin. Accordingly, ACTH(1-24) induced excessive grooming which is blocked by opiate antagonists and is attenuated by gamma-MSH. In addition, gamma-MSH injected into the periaqueductal grey matter of the brainstem of opiate-naive rats elicited symptoms reminiscent of those seen after opiate withdrawal. Gamma-MSH attenuated several effects of intracerebroventricularly administered beta-endorphin (e.g. antinociception, hypothermia, alpha-MSH release) and decreased the acquisition of heroin self-administration. Although gamma-MSH at rather high doses displaced naloxone from its specific binding sites in brain homogenates, it did not interfere with beta-endorphin-induced effects on in vitro muscle preparations (guinea-pig ileum; rat rectum). Interestingly, gamma-MSH induced relaxation of the rat rectum in vitro. It is postulated that gamma-MSH may attenuate beta-endorphin-induced effects by acting via gamma-MSH receptor sites (functional antagonism), although a pharmacological antagonism cannot be excluded as yet.

Adrenocorticotropic Hormone↗

PubMed2002

Chemosensory input and lateralization of brain function in the domestic chick.

One-day old domestic chicks (Gallus gallus domesticus) show concentration-dependent behavioural responses to olfactory cues. In the present study we investigated the lateralized olfactory responses of 1-day-old chicks to the odours of eugenol and iso-amyl acetate. In experiment 1 different concentrations of each odour were presented in repeated trials to chicks housed individually. The odours were presented together with a small coloured bead at which the chick pecked. When tested with the highest concentration of eugenol (100% v/v), the chicks demonstrated more head shaking when their left nostril was occluded (RN; right nostril in use) than when their right nostril was occluded (LN; left nostril in use). No such lateralization occurred in response to iso-amyl acetate. This result was confirmed in a second experiment in which the chicks were tested with unscented stimuli, 100% eugenol and 100% isoamyl acetate. In experiment 3 we found that occluding both the chicks' nostrils abolished the head shaking response to eugenol and to iso-amyl acetate. Thus, the chicks' head shaking responses to the odorants eugenol and iso-amyl acetate are mediated primarily by inputs from within the nasal cavity, and not by oral or occular inputs. The present results are consistent with the hypothesis that there is lateralization to olfactory cues and that it is dependent on the involvement of receptors inside the nasal cavity. We suggest that differences in lateralized olfactory responses to different odours are affected by the relative involvement of intranasal olfactory and trigeminal chemoreceptors.

Animals↗

PubMed1990

Sigma receptors modulate both A9 and A10 dopaminergic neurons in the rat brain: functional interaction with NMDA receptors.

The sigma receptor ligands, (+)-pentazocine and (+)-SKF 10,047, were found to increase dopamine metabolism (DOPAC, HVA) and release (3-MT) in both the striatum and olfactory tubercle of the rat, in a dose-dependent manner, after central as well as peripheral administration. The effect of (+)-SKF 10,047 was stereospecific. The increase in dopamine metabolism was not blocked by naloxone pretreatment, excluding an action via opioid receptors. More interestingly, this modulation was blocked by pretreatment with the NMDA receptor antagonist, CPP. Neither sigma ligand exhibited any affinity for D1 or D2 dopamine receptors or for NMDA, PCP or NMDA-associated glycine receptors. Sigma receptors thus appear to modulate dopaminergic function in both A9 and A10 projections. This modulation appears to involve a functional interaction with NMDA receptors or an NMDA-utilizing synapse downstream to neurons modulated by sigma receptors.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1991

A transient osmotic permeabilization method for the introduction of impermeant molecules into functional brain membrane vesicles.

Mouse brain membrane vesicles (microsacs) were transiently permeabilized by hypo-osmotic shock. This permeabilization method resulted in the encapsulation of both [14C]sucrose and exogenous alkaline phosphatase. The efficiency of this method was estimated by [14C]sucrose encapsulation experiments to be approximately 81%. External membrane binding experiments with the lectin [3H]concanavalin A demonstrate that the microsacs were not inverted by permeabilization. Following permeabilization, the functional integrity of a ligand-gated ion channel, the GABAA receptor complex, was investigated. Muscimol-stimulated 36Cl-uptake experiments show that this receptor retains its functional properties including blockade by the receptor antagonist bicuculline and potentiation by the allosteric modulators flunitrazepam and pentobarbital. The osmotic permeabilization technique described here provides several advantages over other permeabilization methods. These advantages include a high trapping efficiency, the encapsulation of not only small solutes but large membrane impermeant compounds such as enzymes and the functional preservation of at least one transmembrane protein. Furthermore, this method does not require specialized equipment and does not result in large, permanent holes in the plasma membrane.

Alkaline Phosphatase↗

PubMed1996

Abnormal processing of visual motion in dyslexia revealed by functional brain imaging.

It is widely accepted that dyslexics have deficits in reading and phonological awareness, but there is increasing evidence that they also exhibit visual processing abnormalities that may be confined to particular portions of the visual system. In primate visual pathways, inputs from parvocellular or magnocellular layers of the lateral geniculate nucleus remain partly segregated in projections to extrastriate cortical areas specialized for processing colour and form versus motion. In studies of dyslexia, psychophysical and anatomical evidence indicate an anomaly in the magnocellular visual subsystem. To investigate the pathophysiology of dyslexia, we used functional magnetic resonance imaging (fMRI) to study visual motion processing in normal and dyslexic men. In all dyslexics, presentation of moving stimuli failed to produce the same task-related functional activation in area V5/MT (part of the magnocellular visual subsystem) observed in controls. In contrast, presentation of stationary patterns resulted in equivalent activations in V1/V2 and extrastriate cortex in both groups. Although previous studies have emphasized language deficits, our data reveal differences in the regional functional organization of the cortical visual system in dyslexia.

Adult↗

PubMed1994

[The clinico-neurophysiological study of the effect of cerebrolysin on brain function in the acute and early recovery periods of hemispheric ischemic stroke].

Thirty patients with acute ischemic stroke and at early terms of postapoplectic recovery received cerebrolysin in daily doses 10, 20 and 30 ml for 5 days or 10 ml, i. v. for 10 days, respectively. The patients were examined for neurological status and cerebral function. In acute stroke the highest effect occurred in the affection of moderate severity. In severe stroke the drug stimulated recovery of impaired functions which tended to restore more quickly than in control subjects. In early convalescents cerebrolysin improved motor functions. Details of the results of the combined neurophysiological examination in the course of the treatment are discussed.

Acute Disease↗