[Evolutionary logic of functional brain asymmetry].
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Biological Evolution↗
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From the head to the heart: some thoughts on similarities between brain function and morphogenesis, and on their significance for research methodology and biological theory.
A broad review of the phenomena of morphogenesis and of brain function, and of the history of research in these two areas, suggests that there are quite striking similarities between the two sets of biological phenomena. Among other things, both reflect the interaction of internally complex components at several levels of organization, display variance as an essential characteristic, and incorporate information from the environment. It is argued that reductionist approaches are inadequate to deal with fundamental problems of either morphogenesis or brain function, and alternative foundations for research strategy and tactics are discussed. Attention is also given to the question of why morphogenesis and brain function are so similar, and it is suggested that this may reflect the existence of rules of information acquisition, transmission, and storage to which both are subject. Variance, it is argued, is an essential component of information acquisition processes, and hence of biological integrity, at all levels of organization.
Animals↗
Effects of corticotropin releasing hormone on human brain function: an analysis based on auditory evoked potentials.
There is evidence that the peptides derived from proopiomelanocortin as well as the neurohypophyseal hormones exert important and substantial effects on brain functions after intracerebroventricular and peripheral administration. This led us to study the effects of intravenous hCRH on brain functions in humans using electroencephalographic techniques. In our experience the event-related potentials (e.g. auditory evoked potentials) provide a sensitive and accurate assay systems to study such effects of peptides. Male volunteers were tested in a dichotic listening paradigm, providing electrophysiological measures of selective attention. Human CRH (50 micrograms/hr i.v.) augmented selective attention as indicated by an increased difference between evoked potential waveforms to attended and to unattended stimuli. The opposite results, a decrease in selective attention, was observed after treatment with the behavioral active fragment of adrenocorticotropin, ACTH 4-10. In comparison to ACTH 4-10, lysine-vasopressin, and cortisol, CRH displayed a unique pattern of influences on event related potentials. From these results we conclude that CRH can affect brain function in man and does so by a direct action on the brain and not only by stimulating the release of other behavioral active hormones.
Adrenocorticotropic Hormone↗
[Brain function monitoring].
EEG and multimodal evoked potentials are currently the most frequently used methods of brain functioning monitoring in severely acute primary or secondary brain damage. Development or regression of brain function disturbances can be reliably assessed in this way. The methods are suitable for early diagnosis of intracranial complications and contribute to diagnosis of irreversible loss of cerebral function. They are also useful for early prognosis assessment. EEG and evoked potentials can be monitored at the bed-site. If there are no technical facilities for long-term EEG monitoring, repeated conventional single tracings are of value in these cases. When both the acoustic evoked brain stem potentials and the early somatosensory potentials are to be examined, the possibility exists to differentiate between hemispheric and brain stem damage and to use these results for prognosis assessment.
Brain↗
Some general physiological principles of the human brain functioning.
Implantation of electrodes into the human brain for diagnosis and therapy of different brain disorders enabled the revelation of some general and specific regularities in the brain functioning which, being properly accounted for, may promote further more efficient brain research with both invasive and non-invasive techniques. This is a discussion of three major principles revealed during comprehensive study of the human brain, including stimulation and recording of the broad range of physiological processes both in a relaxed state and when performing a set of psychological tests. (1) The presence of the flexible links in the cerebral systems subserving complex activity; (2) cerebral restrictive and protective mechanisms; (3) the ability of certain brain areas to respond selectively to the erroneous recognition of a given type of activity--error detection.
Brain↗
[Effects of anesthesia on higher brain functions in the elderly].
Sixty-four patients aged over 60 about to undergo elective surgery of the lower limbs were allocated at random to two groups, one with general anaesthesia, the other with local/regional anaesthesia, in order to compare the effects of these two types of anaesthesia on superior brain functions. The two groups were similar in age, disease, treatment and risk from anaesthesia. Superior brain functions were evaluated by means of a score 24 hours before, then 24 hours and 7 days after the operation. The mean preoperative score was 26.3 +/- 3.4 for the local/regional anaesthesia group and 27.3 +/- 2.6 for the general anaesthesia group, and it remained the same throughout the investigation in both groups. The score decreased to pathological values (less than or equal to 20) in 4 patients from the local/regional anaesthesia group, and this fall was associated with trans- and postoperative incidents (haemorrhage, cardiorespiratory arrest, confusion after receiving pethidine, cardiac decompensation). This study shows that alterations of the superior brain functions are probably related to trans and postoperative incidents rather than to the type of anaesthesia administered.
Aged↗
Brain function in patients with cerebral fat embolism evaluated using somatosensory and brain-stem auditory evoked potentials.
In two victims of traffic accidents with broken bones and fat embolism, serial recordings of somatosensory evoked potentials (SEPs) and brain-stem auditory evoked potentials (BAEPs) were examined to assess brain function. Initial SEPs and BAEPs revealed normal subcortical components, while the late cortical components of SEPs were abolished, findings indicative of diffuse dysfunction of grey rather than of white matter. As the neurological functions became normal, the late components appeared. It is concluded that while absent late components of SEPs do reflect cortical dysfunction, they are not necessarily associated with a poor prognosis. Repetitive recordings of SEPs appear to be a useful tool for assessing the neurological condition and the prognosis of patients with cerebral fat embolism.
Adult↗
The effect of methadone on fetal brain function.
The effect of methadone on fetal brain function in terms of the electroencephalogram (EEG) was studied in eight short-term fetal sheep experiments by single injections of 5 to 20 mg. of methadone into the fetal circulation. Plasma methadeone concentrations (determined by radioimmunoassay) greater than 0.065 mg. per cent were associated with an immediate brief decrease in carotid blood flow, a rapid decrease in frequency and amplitude in the EEG that occasionally became isoelectric but recovered, and immediate and relatively prolonged bradycardia. Similar cardiovascular observations were obtained with plasma methadone concentrations less than 0.065 mg. per cent, but the EEG changes were either minimal or not observed. These results indicate that uptake of methadone by the fetal brain is rapid and that electrical activity and heart rate are affected.
Animals↗
The effect of brain function on coherence patterns in the bipolar EEG.
Studies of the functional organization of the brain based on measurements of coherence in the EEG have, in the past, suffered from a methodological defect which has made interpretation of the results difficult. The effect involved is the use of an active common reference for the recording of the EEG. As a consequence, inferences related to the functional connectivity of brain between the non-referential sites using coherence have probably been wrong. To avoid the problem with the common reference, we have used bipolar derivations of the EEG and used measurements of coherence to reflect synchrony not between individual sites but between regions of the brain. The EEGs in a population of normal volunteers were examined with respect to coherence. Changes in the patterning of coherence were induced by utilizing EEGs from the volunteers during 3 different functional brain states. The first of these was the resting state, the second the verbal motor state and the third, the spatial motor state. The stepwise discriminant analysis method was used to study differences in the patterning of coherences in the 3 states. The results show that the spatial motor state was the most distinct in this regard amongst the 3 states. They results also interpreted as indicating that changes in the patterning of coherence from that in the resting state consisted of both functionally specific and functionally non-specific components.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
A behavioral quantal theory of brain function: an alternative to Lashley's continuity theory of mass action.
A behavioral quantal theory of brain function is formulated on the basis of a newly discovered step-wise relationship invariably present among the findings of three experiments by Tsai, et al. on the effects of (1) cerebral decortication, (2) cranial x-radiation, as well as (3) insulin, metrazol, and electroconvulsive shocks upon white rats' adaptive behavior during their learning of successive habit reversals and one-trial reversal problems. Confirmatory results from earlier investigators who studied effects of various current strengths of ECS upon learning and retention of various maze habits are also cited in support of the behavioral quantal theory of brain function which is proposed here as a close-up, more refined alternative to Lashley's continuity theory of mass action.
Animals↗
Brain functional imaging in senile psychopathology.
Quantified electroencephalogram (EEG) and regional cerebral blood flow (rCBF) measurements are reliable and currently employed techniques in the functional exploration of the aging brain; they can be routinely employed, since discomfort to the patient is minimal. Topographical analysis of EEG and rCBF results is performed in our laboratory by a fully automated mapping system, which also enables statistical comparisons in real time. The goal of our study is to ascertain if there are systematic modifications in the topographic distribution of rCBF and EEG parameters in normal aging, dementia, cerebrovascular disease and in conditions of increased risk for cerebral pathology (e.g. hypertension). Dementias and cerebrovascular pathologies present characteristic brain functional abnormalities, which can be detected by comparing the patient data to an age-matched normal population by the appropriate statistical tests; therefore, the accurate selection of healthy aged controls appears as a crucial issue in order to improve the sensitivity of statistics.
Adult↗
A model of brain function: its implications for psychiatric research.
Much current research in psychiatry proceeds in the absence of an integrated model of brain function. It is based instead on the effort to relate clinical syndromes to single, localised abnormalities in the brain. Such an approach is inconsistent with existing data, inadequate for linking research findings with clinical practice, and, probably, fundamentally misdirected. A model of brain function is presented that is based on Luria's notion of cerebral functional systems and on the proposition that the neural substrates of emotion are those processes that integrate different brain regions. Some of the implications of this model for research are discussed.
Behavior↗
Concussive methods of pre-slaughter stunning in sheep: effects of captive bolt stunning in the poll position on brain function.
The effectiveness of captive bolt stunning in the poll position was evaluated in eight anaesthetised sheep. Brain function following shooting was assessed using cortical visual evoked responses (VERs). Immediately following shooting, VERs were abolished in all sheep. However, in five of the sheep, VERs gradually recovered; responses became evident in these animals in a mean (+/- SE) time of 50 +/- 16.7 seconds. These results suggest that captive bolt shooting in the poll position can be associated with rapid recovery of brain function. Because such recovery could be associated with return of sensibility, shooting in the poll position should only be used when essential (ie, in horned animals) and then always followed promptly by sticking.
Animals↗
[The effects of post-ischemic delayed hypoperfusion on the process of recovery of brain function].
The author studied the effect of post-ischemic delayed hypoperfusion on the recovery process of brain function after complete cerebral ischemia in a dog model in which the existence of PDH had been shown previously by the author, using nicardipine as a tool to ameliorate the PDH, the effect of the drug also having been demonstrated by the author in the previous study. Twenty-four dogs underwent 15 min complete cerebral ischemia using aortic clamping method with aorto-atrial bypass formation. EEG (for 16 h) and brain functions, awakening, cranial nerve reflexes, motor functions, behaviors and respiratory functions were evaluated using neurological deficit score (NDS) periodically (for 120 h) after ischemia. Eight dogs (1 microgram group) received nicardipine 1 microgram.kg-1.min-1 for 4 h following 10 micrograms bolus iv injection 5 min after declamping of aorta, another 8 dogs (2 micrograms group) received 10 micrograms + 2 micrograms.kg-1.min-1 nicardipine in the same manner as group 1, and the remaining 8 served as controls. In 1 microgram group the first appearance of EEG activities after ischemia was earlier than control group (41 +/- 11 vs 80 +/- 33 min), and also the appearance rate of alpha waves was higher than the controls (87.5% vs 25%) 16 h after declamping of aorta. NDS scores for awakening, behavior, and respiratory functions were better in 1 microgram than the controls between 36 and 48 h post-ischemia, but there were no significant changes in the scores between the two groups 120 h after ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Functional brain imaging in the evaluation of psychiatric illness.
In the past century, the field of psychiatry has undergone major changes. During this time, significant advancements in both diagnosis and treatment have occurred. Medical brain imaging using structural and functional brain imaging techniques have contributed, in part, to a better basic understanding of psychiatric disease and to an improving diagnostic approach. Computed tomography and magnetic resonance imaging have supplied limited, but useful insight regarding structural alterations in schizophrenia and the affective disorders. Position emission tomography imaging has already made a major contribution in the assessment of schizophrenia and affective disorders. Single-photon emission computed tomography (SPECT), which is currently more widely available, should contribute more to psychiatric disease evaluation in the future. Recent advances in SPECT technology in the areas of improved instrumentation--such as multidetector and ring detector systems and new radiopharmaceuticals including new rCBF markers and receptor site imaging agents--have contributed to significant improvements in the SPECT imaging technique. At the present time, SPECT has been shown to be feasible and useful in the evaluation of acute and chronic psychiatric and demented states. As SPECT technology continues to evolve, further refinements in this diagnostic capability can be anticipated.
Brain↗
The concept of coupling blood flow to brain function: revision required?
A tight coupling exists between brain function and cerebral perfusion in most situations. The Roy and Sherrington hypothesis has been widely accepted to account for the phenomenon: increased neuronal metabolic activity will give rise to the accumulation of vasoactive catabolites, which decrease vascular resistance and thereby increase blood flow until normal homeostasis is reestablished. However, the hypothesis does not account for the disproportionate increase in flow that occurs in a number of circumstances. There are additional difficulties in reconciling more recent experimental data with the Roy and Sherrington hypothesis. In this review we direct attention toward the rich perivascular nerve supply to all parts of the cerebral circulation as possibly being an alternative control system allowing for rapid parallel changes in flow and neuronal activity.
Animals↗
Physiological asymmetry of brain functions--its influence on the lateralization, symptomatology and course of the epileptic process.
Lateralization of the epileptic process in a group of 152 subjects and the relationship of epilepsy to the lateralization of brain functions was studied in smaller groups of 108 and 56 subjects. A unilateral epileptic process in the temporal limbic structures of the brain is localized in the left half of the brain twice (in 64.5%) to four times (in 80.8%) as often as in the right half. The greater the asymmetry of physiological brain functions--in particular motor and verbally symbolic functions--the more is this tendency pronounced. An epileptic process in temporal limbic structures of the left half of the brain is manifested more often in primarily generalized epileptic seizures with initial sudden and complete loss of consciousness. Episodic spike-and-wave activity, which is the typical electroencephalographic correlate of primarily generalized seizures, or of the thalamocortical aetiopathogenetic component of the epileptic process, is often asymmetrical in amplitude, which in 68.1% of these cases is twice as high over the left hemisphere. An epileptic process in subcortical structures of the right hemisphere impairs physiological asymmetry of emotive facial mimicry (with preponderance of mimic reactions on the left) and in 68.4% of the cases causes atypical preponderance of emotive mimicry in the right half of the face. A unilateral epileptic process in subcortical structures of the left half of the brain has a more favourable course and more hopeful prognosis in 70.4% of the cases, while the course of a right-sided process is worse in 67.6%.
Action Potentials↗
Functional brain mapping using magnetic resonance imaging. Signal changes accompanying visual stimulation.
Easily detectable (5%-20%) transient increases in the intensity of water proton magnetic resonance (MR) signals in human primary visual cortex were observed during visual stimulation in gradient echo images at 4-T field strength. The signal intensity increases were predominantly restricted to areas containing gray matter and were used to produce high-spatial-resolution human functional brain maps. Time dependence of the functional brain maps also was monitored during visual stimulation using images acquired every approximately 5 seconds; these images with high spatial and temporal resolution demonstrated that photic stimulation first resulted in signal increases in a large area of the visual cortex followed by a reduction in the size of the area, and that signal intensity increases in the gray matter were time dependent. Reducing the image acquisition echo times reduced the amplitude of the fractional signal change, suggesting that it is produced by a change in T2 or T2*. The amplitude, sign, and echo time dependence of these intrinsic signal changes are consistent with the idea that neural activation increases regional cerebral with the idea that neural activation increases regional cerebral blood flow (rCBF) with a concomitant increase in venous blood oxygenation.
Brain Mapping↗