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At least 271 records · Page 15Linked to original sources
PubMed1998

Reduced prefrontal and increased subcortical brain functioning assessed using positron emission tomography in predatory and affective murderers.

There appear to be no brain imaging studies investigating which brain mechanisms subserve affective, impulsive violence versus planned, predatory violence. It was hypothesized that affectively violent offenders would have lower prefrontal activity, higher subcortical activity, and reduced prefrontal/subcortical ratios relative to controls, while predatory violent offenders would show relatively normal brain functioning. Glucose metabolism was assessed using positron emission tomography in 41 comparisons, 15 predatory murderers, and nine affective murderers in left and right hemisphere prefrontal (medial and lateral) and subcortical (amygdala, midbrain, hippocampus, and thalamus) regions. Affective murderers relative to comparisons had lower left and right prefrontal functioning, higher right hemisphere subcortical functioning, and lower right hemisphere prefrontal/subcortical ratios. In contrast, predatory murderers had prefrontal functioning that was more equivalent to comparisons, while also having excessively high right subcortical activity. Results support the hypothesis that emotional, unplanned impulsive murderers are less able to regulate and control aggressive impulses generated from subcortical structures due to deficient prefrontal regulation. It is hypothesized that excessive subcortical activity predisposes to aggressive behaviour, but that while predatory murderers have sufficiently good prefrontal functioning to regulate these aggressive impulses, the affective murderers lack such prefrontal control over emotion regulation.

Affect↗
PubMed2003

How accurate is magnetic resonance imaging of brain function?

Since it was introduced a decade ago, functional magnetic resonance imaging (fMRI) has come to dominate research on the human brain. However, fMRI maps are based on secondary metabolic and hemodynamic events that follow neuronal activity, and not on the electrical activity itself. Therefore, the representation provided by fMRI cannot be assumed a priori to be exact. The accuracy of these maps depends on the spatial extent of the metabolic and hemodynamic changes induced by neuronal activity, and the role played by the vasculature in converting these changes to signals detected by magnetic resonance imaging. Significant progress has been made in both areas, suggesting that it is possible to obtain both spatially accurate and quantitative data on brain function from magnetic resonance methodologies.

Brain↗
PubMed1985

Biochemical and neuropsychological effects of elevated plasma phenylalanine in patients with treated phenylketonuria. A model for the study of phenylalanine and brain function in man.

Phenylketonuria provides a human model for the study of the effect of phenylalanine on brain function. Although irreversible mental retardation is preventable through newborn diagnosis and dietary phenylalanine restriction, controversy exists regarding the effects of increased concentrations of phenylalanine in older patients. We have studied ten older, treated, phenylketonuric patients using a triple-blind, multiple trials, crossover design. Each patient was tested at the end of each of three 1-wk periods of high or low phenylalanine intakes. Tests included a repeatable battery of neuropsychological tests, analysis of plasma amino acids, and measurement of urine amino acids, phenyl organic acids, dopamine, and serotonin. In all 10 patients plasma phenylalanine rose (900-4,000 microM). In 9 of 10 patients there was an inverse relationship between plasma phenylalanine and urine dopamine excretion. When blood phenylalanine was elevated, these patients had prolonged performance times on neuropsychological tests of higher but not lower integrative function. Urinary serotonin fell during phenylalanine loading in six patients. The concentration of phenylacids in the urine was not proportional to the plasma phenylalanine at concentrations below 1.5 mM. In one patient, neither performance time nor dopamine excretion varied as blood phenylalanine rose or fell. We interpret these data as follows: blood phenylalanine above 1.3 mM impairs performance on neuropsychological tests of higher integrative function, this effect is reversible, and one mechanism may involve impaired biogenic amine synthesis.

Adolescent↗
PubMed1986

Role of the supraoptic decussation in the development of asymmetry of brain function in the chicken.

The supraoptic decussation plays an important role in the development of asymmetry of brain function for visual discrimination learning in the chicken. Lesioning the decussation on day 2 has no effect on the asymmetry normally revealed by unilaterally treating either the left or right forebrain hemisphere with cycloheximide on day 4 of life. However, the lesion removes the asymmetry revealed by cycloheximide treatment on day 8 and reverses that revealed by treatment on day 10, albeit to a lesser extent. The asymmetry of learning performance between the left and right eyes present in untreated chickens tested monocularly in the second week of life is also removed by lesioning the supraoptic decussation. Thus, in the first week of life functional asymmetry is present but not dependent on left-to-right side coupling via the supraoptic decussation. The difference between lesioning during the first and second week of life may relate to the relative degree of maturation in the supraoptic decussation.

Age Factors↗
PubMed1990

Improvement of brain function in hemodialysis patients treated with erythropoietin.

To evaluate the effects of recombinant human erythropoietin (rHuEPO) on brain function, 15 chronic hemodialysis patients were studied by event-related P300, stimulus-related evoked potentials, and trailmaking before (hematocrit 22.7%) and after rHuEPO (hematocrit 30.6%). P300 peak latency elicited by a tone discrimination paradigm improved (391 before vs. 366 ms after; Cz = vertex; P less than 0.01) confirming beneficial effects on cerebral cognitive processing. P300 amplitude (13.6 vs. 15.8 microV; P = 0.06) and trailmaking tended to improve (55 vs. 43 s). P300 measures were influenced by low hemoglobin levels before rHuEPO (P less than 0.01), suggesting that severe anemia may contribute to uremic brain dysfunction. Furthermore, decrease of stimulus-related auditory brainstem I-V interpeak latency (4.28 before vs. 4.17 ms after; P less than 0.05) and increase of somatosensory N20/P25 amplitude (4.8 vs. 7.0 microV; P less than 0.05) pointed to improvement of sensory pathways by mechanisms unrelated to cognition. Brain dysfunction in chronic hemodialysis patients may, beside other factors, in part be caused by severe anemia and can be improved by rHuEPO treatment.

Anemia↗
PubMed1999

The role of neural activity in synaptic development and its implications for adult brain function.

In much of the developing nervous system, electrical activity guides the formation of neural connections, with lasting effects on adult brain function. Epilepsy, a defect in neuronal excitability, might result from abnormal patterns of activity in the young brain. Many connections are organized by selective stabilization of synapses when they are activated simultaneously on the same postsynaptic cell during a sensitive period in early life. This process often involves calcium entry through the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor. The magnitude of the current passed by this receptor depends on its subunit composition, which varies with age and brain region. Although receptor configurations that admit large calcium currents are permissive of synaptic plasticity, they also increase neural vulnerability to excitotoxic cell death. In most regions of developing brain, activity that can drive NMDA receptors initially is low and increases with maturation. Thus, the replacement of NMDA receptors that flux large calcium currents during early periods of synaptic organization with NMDA receptor subtypes that flux less calcium as synapses become more active, more effective, and less plastic allows maturing neurons to maintain optimal levels of intracellular calcium in the face of drastic developmental changes in their inputs. We have proposed that this transition in NMDA receptors from high to low calcium permeabilities is itself activity dependent. This idea is supported by data showing that many synaptic proteins, including receptor subunits, can be regulated by activity. Cultured cerebellar granule neurons require NMDA receptor stimulation for survival and differentiation, which may replicate the activation provided by the arrival of mossy fiber innervation in vivo. In these cultures, chronic depolarization and glutamate or NMDA treatment induces more mature NMDA receptor subunit expression patterns and function and also increases the expression of several gamma-aminobutyric acid type A (GABAA) receptor subunits, changing that receptor's function. In addition, evidence from in vivo studies indicates that synaptic maturation itself may depend on NMDA receptor activity. During the formation of topographic connections between the retina and superior colliculus (SC) of young rats, chronic local application of the competitive NMDA receptor antagonist +2-amino-5-phosphonovalerate (D-APV) blocks the normal developmental up-regulation of NMDA receptor subunit 1 (NR1) mRNA and nitric oxide synthase activity, as well as maturation of calcium and calmodulin-dependent kinase distribution, activity, and substrate phosphorylation. Together, these recent molecular findings suggest that chronic seizure disorders could result from any of a variety of early developmental events. Any disturbance that locally perturbs regulation of NMDA receptors or the temporal correlations in synaptic activity that drive these receptors has the potential to alter the normal development of local circuitry and the critical balance of inhibition and excitation required to contain seizure activity.

Aging↗
PubMed1999

Neural modeling, functional brain imaging, and cognition.

The richness and complexity of data sets acquired from PET or fMRI studies of human cognition have not been exploited until recently by computational neural-modeling methods. In this article, two neural-modeling approaches for use with functional brain imaging data are described. One, which uses structural equation modeling, estimates the functional strengths of the anatomical connections between various brain regions during specific cognitive tasks. The second employs large-scale neural modeling to relate functional neuroimaging signals in multiple, interconnected brain regions to the underlying neurobiological time-varying activities in each region. Delayed match-to-sample (visual working memory for form) tasks are used to illustrate these models.

Journal Article↗
PubMed2001

[Long-term correction of brain function. Prospects of immunologic approaches].

Among various approaches to long-term correction of the highest functions of the brain there are two methods that are particularly promising. These included: 1) induction of autoantibodies against the enzymes involved in the metabolism of neuroregulators by means of immunization of respective heterologous enzymes; 2) immunization by covalent conjugates of monomolecular neurotropic compounds and neuropeptides with antigen carriers. The investigations of both methods are reviewed and illustrated in experiments on albino rats during alcoholization and some other processes of pathological behavior formation. Evidence is provided for that behavior can be corrected for several months or longer.

Alcoholism↗
PubMedDate not supplied

[New approaches in correcting disorders of higher integrative brain functions in the pharmacotherapy of arterial hypertension with propranolol].

In experiments on rats it is found that propranolol in a dose of 2 mg/kg has a negative effect on higher integrative functions of the brain. Nootropics--pyracetam (200 mg/kg), AKF-94 (20 mg/kg), PIR-87-6-O (50 mg/kg) and actoprotector bemityl (40 mg/kg)--normalized orientative-trying behavior, memory, and emotionality of the animals. A possible mechanism of the drug action and prospects of their clinical application are discussed.

Animals↗
PubMed1993

A single photon emission computerised tomography study of regional brain function in elderly patients with major depression and with Alzheimer-type dementia.

The uptake, at rest, of 99mTc-exametazime into different brain regions was compared using SPECT for 20 elderly subjects with major depressive disorder, 20 with Alzheimer-type dementia, and 30 age-matched normal volunteers. Uptake was referred to calcarine-occipital cortex as a reference sensory area. Cross-sectional differences between the three groups were highly statistically significant, but reflected primarily the reductions in cortical uptake in the Alzheimer group. A detailed comparison of depressed patients and controls identified decrements in anterior cingulate, temporal and frontal cortex and in caudate and thalamus in men only. These decrements were correlated with impairment of performance on a trail-making task, but were also associated with continuing treatment with antidepressants or benzodiazepines. However, most depressed patients had quantitatively normal scans for posterior parietal association cortex, and this suggests that SPECT may find a limited role in the differential diagnosis of depression and dementia. The reduced brain function in some depressed patients may parallel the findings from studies of brain structure in elderly depressives; there was between good outcome at 6-18 months and increased tracer uptake in subcortical areas.

Age of Onset↗
PubMed1988

Blood glucose and brain function: interactions with CNS cholinergic systems.

We recently found that glucose injections attenuate amnesia and hyperactivity produced by scopolamine, a muscarinic antagonist. The present study examined whether glucose would augment behavioral effects produced by a muscarinic agonist, physostigmine. In experiment I, doses were first determined for which neither glucose (10 mg/kg) nor physostigmine (0.05 mg/kg) altered scopolamine-induced hyperactivity. However, combined glucose-physostigmine injections significantly reduced scopolamine hyperactivity. Experiment II evaluated the effects of glucose on physostigmine-induced tremors. Glucose (10, 100, and 250 mg/kg) or saline injections were given 20 min before physostigmine injections (0.4 or 0.05 mg/kg). Observations of glucose effects on the severity of physostigmine-induced tremors were then obtained at 5-min intervals for 25 min after physostigmine injections. Glucose (100 mg/kg) significantly facilitated the onset of tremors when injected before either dose of physostigmine, and augmented (at 100 and 250 mg/kg) tremor severity when injected before the lower dose of physostigmine. These findings indicate that glucose can facilitate the actions of a cholinergic agonist on two behaviors, locomotor activity and tremors, adding support to the view that circulating glucose levels can modulate central cholinergic function. More generally, the results provide additional evidence that circulating glucose levels can influence brain function.

Animals↗
PubMed1999

Structural and functional brain asymmetries in human situs inversus totalis.

OBJECTIVE: To determine whether individuals with situs inversus totalis (SI), a condition in which there is a mirror-image reversal of asymmetric visceral organs, have alterations in brain asymmetries. BACKGROUND: The human brain is asymmetric in structure and function. Although correlations between anatomic asymmetries and functional lateralization in human brain have been demonstrated, it has been difficult to further analyze them. Characterization of asymmetries of brain structure and function in SI might advance the understanding of these relationships. METHODS: Using anatomic and functional MRI techniques, we analyzed asymmetries in the brains of three individuals with SI. RESULTS: Two major anatomic asymmetries of the cerebral hemispheres, the frontal and occipital petalia, were reversed in individuals with SI. In contrast, SI subjects had left cerebral hemisphere language dominance on functional MRI analysis as well as strong right-handedness. CONCLUSION: These observations suggest that the developmental factors determining anatomic asymmetry of the cerebral petalia and viscera are distinct from those producing the functional lateralization of language.

Adult↗
PubMed1996

The central adaptation syndrome: psychosocial stress as a trigger for adaptive modifications of brain structure and brain function.

This review makes an attempt to combine data from biological and psychosocial stress literature and to suggest an alternative interpretation of the relationship between stress and disease. It rearranges the presently available knowledge on the short- and long-term effects of stress on many different aspects of brain structure and brain function in the form of a new conceptualization of the biological role of the stress response. The higher associative brain structures are not only the sites in which environmental and psychosocial demands are recognized and from which a less or more systemic, i.e. controllable or uncontrollable, stress response is initiated. They are also the sites which are primarily affected in the course of the stress response: the stress response acts as a trigger for the adaptive modification of the structure and the function of the brain of higher vertebrates and serves thus to adjust, in a self-optimizing manner, the behavior of an individual to the ever-changing requirements of its external world. This novel concept summarizes a large amount of information into a framework that lends itself to testable strategies for future research.

Adaptation, Physiological↗
PubMed2001

Effects of estrogen deficiency on brain function. Implications for the treatment of postmenopausal women.

A growing body of evidence suggests that postmenopausal estrogen deficiency accelerates brain aging and increases the risk of various neurodegenerative processes, including Alzheimer's disease. Recent preclinical and clinical studies have indicated that estrogen has positive effects on brain homeostasis by preserving neural plasticity and the neurotransmitter pathways involved in learning, memory, and balance. In this article, Dr Birge and his coauthors address the effects of estrogen on brain function and discuss their implications for the use of selective estrogen receptor modulators, particularly tamoxifen and raloxifene, in postmenopausal women.

Aging↗
PubMed1998

Sperry's concept of mind as an emergent property of brain function and its implications for the future of humankind.

Sperry's proposal that subjective experience plays a major role in brain function and in the emergence of mind, consciousness and human values represent a challenge to behaviorism as the dominant force in psychology. Mind is viewed as an emergent property of the brain, generated from and dependent upon neural activity, but nonetheless separate from it. Macrodeterministic factors result in the evolution of human values, which represent a critical key to world change. Two major conferences resulted from Sperry's challenge to the scientific community. The Trieste Conference led to a 'Declaration of Human Responsibilities', presently under consideration by the United Nations as a corollary to the 'Declaration of Human Rights'. The Japan Conference inspired work toward a Network University of the Green World, in which computer networking will support international communication in areas of environmental concern.

Brain↗
PubMed1998

Functional brain imaging in apraxia.

BACKGROUND: An extensive literature describes structural lesions in apraxia, but few studies have used functional neuroimaging. We used positron emission tomography (PET) to characterize relative cerebral glucose metabolism in a 65-year-old, right-handed woman with progressive decline in ability to manipulate objects, write, and articulate speech. OBJECTIVE: To characterize functional brain organization in apraxia. DESIGN AND METHODS: The patient underwent a neurological examination, neuropsychological testing, magnetic resonance imaging, and fludeoxyglucose F 18 PET. The patient's magnetic resonance image was coregistered to her PET image, which was compared with the PET images of 7 right-handed, healthy controls. Hemispheric regions of interest were normalized by calcrine cortex. RESULTS: Except for apraxia and mild grip weakness, results of the neurological examination were normal. There was ideomotor apraxia of both hands (command, imitation, and object) and buccofacial apraxia. The patient could recognize meaningful gestures performed by the examiner and discriminate between his accurate and awkward pantomime. The magnetic resonance image showed moderate generalized atrophy and mild ischemic changes. Positron emission tomographic scans showed abnormal fludeoxyglucose F 18 uptake in the posterior frontal, supplementary motor, and parietal regions, the left affected more than the right. Focal metabolic deficit was present in the angular gyrus, an area hypothesized to store conceptual knowledge of skilled movement. CONCLUSIONS: Greater parietal than frontal physiological dysfunction and preserved gesture recognition are not consistent with the theory that knowledge of limb praxis is stored in the dominant parietal cortex. Gesture comprehension may be more diffusely distributed.

Aged↗
PubMed2001

Effects of QiGong on brain function.

QiGong is an ancient and widely practiced Chinese meditation exercise. We studied the effects of QiGong on brain function with modern neuromonitoring tools in two subjects. In a male QiGong master (extremely trained practitioner), the technique induced reproducible changes in transcranial Doppler sonography, EEG, stimulus-induced 40 Hz oscillations, and near-infrared spectroscopy findings. Similar effects were seen after the application of multimodal stimuli and when the master concentrated on intense imagined stimuli (e.g. 22.2% increase in mean blood flow velocity (vm) in the posterior cerebral artery, and a simultaneous 23.1% decrease of vm in the middle cerebral artery). Similar effects were seen in the female subject. Neuromonitoring during QiGong appears able to objectify accompanied cerebral modulations surrounding this old Chinese meditation exercise.

Acoustic Stimulation↗