A linear theory for global electrocortical activity and its control by the lateral hypothalamus

A linear model for electrocortical waves and their control by the lateral hypothalamus is proposed. It is argued that such a linear model is not in contradition to non-linearity of neural elements on the microscopic scale. Telencephalic structures are treated as a mass of linked oscillators generating activity with a number of resonant modes. The lateral hypothalamus is regarded as controlling damping of activity in the telencephalic mass, and therefore exerting a specific parametric control over all signal processing in the cortical networks. An initial test is proposed to assess the constancy of telencephalic natural frequencies, with variation in lateral hypothalamic damping.     

Inference of a stable dispersion relation for electrocortical activity controlled by the lateral hypothalamus

A second test is undertaken for a theory of linear wave motion in electrocortical waves, under lateral hypothalamic control via regulation of damping. This test invokes a general property of linear systems, namely that wave motion with characteristic natural frequencies implies fixed phase velocities associated with each wavelength, independent of the changes in hypothalamic input. A means of testing the invariance of this dispersion relation at the point of recording is derived from a simplified biophysical model for waves in a dipole layer. The method avoids some problems implicit in direct spatio-temporal wave analysis. Results confirm that the model under test is internally consistent, and is also consistent with other findings concerning the origin and spatial nature of the EEG.     

Contributions of noradrenergic neurones of the locus coeruleus to the temporal damping of linear electrocortical waves

The preceeding paper (Wright et al. 1985a) gives evidence that mesotelencephalic dopaminergic neurones regulate gross electrocortical waves with linear properties, by influencing the strength of their driving signals and temporal damping. The present study further generalises the findings to ascending noradrenergic neurones, which have different fields of termination to dopaminergic fibres. It is shown that: Estimates of the major groups of natural frequencies for the telencephalic system obtained from curve-fitting the ratio changes in the power spectrum attributable to unilateral noradrenergic neurone lesion, are again centered about the frequencies of the major cerebral rhythms. Estimates of electrode transfer characteristics, using parameters obtained from curve fitting ratio changes in power, in conjunction with the raw left and right power spectra, are again found to be equal left and right, as required by the theoretical derivation. Changes in relative amplitude of electrocortical waves and their relative phase are significantly in accord with the relationship expected from theory.     

Quantitation of a mass action of dopaminergic neurones regulating temporal damping of linear electrocortical waves

We have previously proposed that electrocortical waves are linear waves, subject to regulation by mesotelencephalic dopaminergic neurones. As a further means to test this theory, selective unilateral lesions of varying extent were made in the nucleii of origin of the dopaminergic mesotelencephalic tract. Changes in the electrocortical power spectrum were assessed by a repeated measure, between hemispheres comparison of ratio changes in power. With increasing unilateral dopamine cell damage, the animals showed increasing contralateral sensorimotor neglect. Curve fitting the ratio changes in power attributable to lesion, showed that estimates of the power of driving signals and the temporal damping moved in reverse directions with increasing extent of lesion, as expected from the theory. A further test was undertaken, to determine whether equal estimates for a transformation of surface signals were obtained from each side. Equality would not be expected if the equation for relative power were invalid. Left and right equality was found for three grades of unilateral lesion.     

Study of electrical activity in the area of the hypothalamic ventromedial nucleus and the lateral hypothalamus of rats fed on a high protein and high fat diet.

The authors studied bioelectric potentials in the area of the hypothalamic ventromedial nucleus and the lateral hypothalamus of rats fed on a standard, a high protein and a high fat diet. On the first 3--6 days after changing from the standard to the high fat and high protein diets, a decrease in the amplitude of electrical activity was recorded in both the areas in question. It was also found that the frequency of electrical activity in the hypothalamic ventromedial nucleus or the lateral hypothalamus rose, after 3 days administration of the high fat or the high protein diet, in correlation to the type of diet, and that, in the frequency spectrum, a change occurred in the proportion of basic frequency in relation to superimposed frequencies distorting it. It was further found that there was a permanent difference between the amplitude of electrical activity in the lateral hypothalamus and the hypothalamic ventromedial nucleus.     

Isocortical Hyperemia and Allocortical Inflammation and Atrophy Following Generalized Convulsive Seizures of Thalamic Origin in the Rat

1. Generalized convulsive seizures can be elicited by a single unilateral microinjection of the cholinergic muscarinic agonist, carbachol, into the specific sites of the thalamus including ventral posterolateral and the reticular thalamic nuclei. The implication of the thalamic specific and reticular neurons is reviewed and discussed.2. On the basis of the c-fos regional expression and well-known efferent and afferent pathways linking these regions, a neuronal network relating the limbic, thalamo–striatal–cortical, and central autonomic systems, was constructed.3. The pattern of Fos immunoreactivity associated with long-lasting isocortical vasodilatation elicited by generalized convulsive seizures in anesthetized rat following cholinergic stimulation of the thalamus can be attributed to both the electrocortical activity and the long-lasting increase in cortical blood flow. We propose that the sustained cerebral cortical blood flow response during convulsive epileptic seizures may implicate intracerebral vasodilatory and vasoconstrictory neural mechanisms. Double-labeled NADPH-d and Fos-positive neurons implicated in maintaining the sustained isocortical vasodilatory response were found in the anterior lateral hypothalamic area. Inhibition of these neurons prevented the increase in cortical blood flow despite an increased metabolic demand manifested by the ictal electrocortical activity.4. Medial temporal lobe atrophy, including hippocampus, amygdala, and parahippocampal gyrus (piriform and entorhinal cortices) are the most common pathology in man. However the origin of medial lobe atrophy remain uncertain. Our results provide evidence that the allocortical microvascular inflammation may be in origin of the neurovascular degenerative processes leading to atrophy.     

Spacetime representation of global electrocortical activity

A model for global electrocortical activity is developed by considering telencephalonic structures as mass of linked oscillators generating activity with a number of resonant modes. Equations for the signals are written in the comoving frame and then transformed into the laboratory frame. The state transition matrix is obtained in the presence of electric and magnetic fields.     

Effects of weak electromagnetic fields on global electrocortical activity

Effects of weak electromagnetic fields are considered on recently proposed covariant and generalized coupling models of global electrocortical activity. A method to calculate the ratio of components of signal velocities is given. First-order shift in frequencies is obtained in the presence of a weak, time-varying magnetic field.     

The central effects of morphine on fetal breathing movements in the fetal sheep

The fetal respiratory and electrocortical effects of 0.6 microgram to 600 micrograms of morphine, administered into the lateral cerebral ventricle, have been studied in chronically catheterised, unanaesthetized fetal sheep at 115-135 days gestation. Morphine at 0.6 microgram had no effect on breathing movements or electrocorticographic activity, and at 6 micrograms induced a period of apnoea (43-122 min) but had no effect on electrocortical activity. Intravenous naloxone (2 mg bolus and infusion of 2 mg/kg/h for 2 h) to the fetus had no effect on this apnoea. Morphine at 60 micrograms induced an initial period of apnoea (30-65 min) followed by episodic but significantly deep breathing movements with no effect on electrocortical activity and at 600 micrograms induced an initial period of apnoea (22-95 min) which was followed by deep, irregular and continuous (126-302 min) breathing movements. During the apnoea electrocortical activity initially remained cyclic, but as apnoea progressed there was a gradual reduction in the voltage of the electrocorticogram to a low voltage state. Intravenous naloxone (2 mg bolus and infusion of 2 mg/kg/h for 2 h) reversed both the respiratory and electrocortical effects. The hyperventilation was also inhibited by hypoxia. Naloxone alone had no effect on fetal breathing activity.     

Effect of Intraventricular Putrescine on Adenosylmethionine Decarboxylase in Rat Hypothalamus and Caudate Nucleus

Effects of intracerebroventricularly injected putrescine on adenosylmethionine decarboxylase activity in rat hypothalamus and caudate nucleus were studied. Doses that lacked the capacity to produce behavioral and electrocortical epileptogenic disorder caused a significant activation of enzyme occurring between 10 and 15 min after injection. The changes in hypothalamic and caudate nucleus enzyme activity after putrescine administration were dose-dependent, and they supported the assumption that limiting putrescine concentration in vivo may play a role in adenosylmethionine decarboxylase regulation.     

The role of hypothalamic ingestive behavior controllers in generating dehydration anorexia: a Fos mapping study

Giving rats 2.5% saline to drink for 3-5 days simply and reliably generates anorexia. Despite having the neurochemical and hormonal markers of negative energy balance, dehydrated anorexic rats show a marked suppression of spontaneous food intake, as well as the feeding that is usually stimulated by overnight starvation or a 2-deoxy-d-glucose (2DG) challenge. These observations are consistent with a dehydration-dependent inhibition of the core circuitry that controls feeding. We hypothesize that this inhibition is directed at those neurons in the paraventricular nucleus and lateral hypothalamic area that constitute the hypothalamic "behavior controller" for feeding rather than their afferent inputs from the arcuate nucleus or hindbrain that convey critical feeding-related sensory information. To test this hypothesis, we mapped and quantified the Fos-immunoreactive response to 2DG in control and dehydrated rats drinking 2.5% saline. Our rationale was that regions showing an attenuated Fos response to 2DG in dehydrated animals would be strong candidates as the targets of dehydration-induced suppression of 2DG feeding. We found that the Fos response to combined dehydration and 2DG was attenuated only in the lateral hypothalamic area, with dehydration alone increasing Fos in the lateral part of the paraventricular nucleus. In the arcuate nucleus and those regions of the hindbrain that provide afferent inputs critical for the feeding response to 2DG, the Fos response to 2DG was unaffected by dehydration. Therefore, dehydration appears to target the lateral hypothalamic area and possibly the lateral part of the paraventricular nucleus to suppress the feeding response to 2DG.     

Amplitude and phase relations of electrocortical waves regulated by transhypothalamic dopaminergic neurones: A test for a linear theory

We have previously proposed that electrocortical activity (EEG) arises as a manifestation of linear waves generated by resonance among telencephalic neurones, and that this activity is controlled in part by ascending neurones from the brain-steim, which regulate the damping of each resonance. The presentexperiments focus on a specific class of ascending neurones, the mesotelencephalic dopaminergic cells, because these cells are thought to mediate important psychological effects, and are conveniently subject to selective lesion. A critical test of the theory is undertaken, by performing selective unilateral lesion, assessing the changes in the power spectrum of the EEG attributable to lesion, and determining whether the changes in phase of the EEG correspond to that predicted from the changes in power. Results support the theory, although the model order applicable in these experiments is inadequate. The consequences of these findings for automata theory, linear network theory and their application to mammalian brains are briefly discussed.     

2Hz和100Hz电针加速脑内三种阿片肽基因表达

我室以往的工作证明２Ｈｚ和１００Ｈｚ电针可引起中枢释放不同种类的阿片肽,本工作试图阐明不同频率的电针是否影响三种阿片肽的基因转录。用地高辛标记的反义ｃＲＮＡ探针进行原位杂交,显示大鼠脑内前脑啡肽原（ＰＰＥ）,前强啡肽强（ＰＰＤ）和前阿黑皮素原（ＰＯＭＣ）ｍＲＮＡ。结果：（１）低、高频电针均不影响ＰＯＭＣ ｍＲＮＡ的水平。（２）对ＰＰＥ的影响,两种频率电针诱导脑干网状结构头端腹内侧区ＰＰＥ ｍＲＮＡ     

Conventional and complex modal analyses of a finite element model of human head and neck

This study employs both the traditional and the complex modal analyses of a detailed finite element model of human head–neck system to determine modal responses in terms of resonant frequencies and mode shapes. It compares both modal responses without ignoring mode shapes, and these results are reasonably in agreement with the literature. Increasing displacement contour loops within the brain in higher frequency modes probably exhibits the shearing and twisting modes of the brain. Additional and rarely reported modal responses such as ‘mastication’ mode of the mandible and flipping mode of nasal lateral cartilages are identified. This suggests a need for detailed modelling to identify all the additional frequencies of each individual part. Moreover, it is found that a damping factor of above 0.2 has amplifying effect in reducing higher frequency modes, while a diminishing effect in lowering peak biomechanical responses, indicating the importance of identifying the appropriate optimised damping factor.     

Distribution of vasoactive intestinal peptide-like and neurophysin-like immunoreactive neurons and acetylcholinesterase staining in the ring dove hypothalamus with emphasis on the question of an avian suprachiasmatic nucleus

Summary Two nuclei, termed here the medial hypothalamic nucleus and the lateral hypothalamic retinorecipient nucleus, are possible homologs of the mammalian suprachiasmatic nucleus. As the mammalian suprachiasmatic nucleus is characterized by a dense concentration of vasoactive intestinal peptide (VIP)-and neurophysin (NP)-immunoreactive neurons and an absence of acetylcholinesterase (AChE) staining, we decided to examine these factors in the ring dove hypothalamus. Neither the medial hypothalamic nucleus nor the lateral hypothalamic retinorecipient nucleus contained either VIP-or NP-like immunoreactive neurons. The lateral hypothalamic retinorecipient nucleus stained darkly for AChE. Although there was some overlap in the distribution of VIP-and NP-like immunoreactive neurons, a clustering of both types into a well defined nucleus was not observed. Therefore, an avian homolog to the mammalian suprachiasmatic nucleus must differ in its chemoarchitecture from that of mammalian species described to date.     

Nuclei and fields of the rabbit hypothalamus]

Common features and distinctions in the structure of certain fields of the rabbit hypothalamus were established on the basis of cytoarchitectonical and cytological analysis. It has been shown that there are three types of nerve cells in the nuclei and fields of the hypothalamus which can be referred to somato-, cyto- and karyochromic elements of the nervous system in accordance with the Nissl classification. All the cellular structures of the hypothalamus can be divided into heteromorphic and isomorphic types. The medial and lateral hypothalamic fields of all the rostro-caudal length of the hypothalamus are referred to the first type. The hypothalamic nuclei occupying its basal part are referred to the second type. On the basis of the obtained data concerning the neuronal composition of the fields and nuclei of the hypothalamus, it can be divided into three zones: the medial zone, including 3 medial hypothalamic fields disposed along the 3d ventricle; the lateral zone comprizing two a lateral hypothalamic fields occupying its lateral parts along its all length and the basal zone including hypothalamic nuclei disposed mainly in the ventral part of the hypothalamus.     

Group-theory classification of oscillations of plasma clusters

Normal oscillations of three-dimensional configurations of dust grains trapped in a spherically symmetric potential well are studied. All possible oscillations of a system consisting of 7–13 grains are classified in terms of group theory. For a Coulomb interaction potential, all the oscillation frequencies are calculated. The frequencies and polarizations of some oscillation modes are obtained for an arbitrary interaction potential.     

The vibrational normal modes of beta-barrels in an IgG antibody molecule.

Based on the quasi-continuity model, and using the method of group theory, we studied the normal vibrations of the VL- and the CHL-beta-barrels in an IgG molecule. We put emphasis on the Raman- and the infrared-active normal modes. The Raman modes we obtained include both the breathing motion mode (or the dominant low-frequency mode) which corresponds to the maximum peak in the Raman spectrum, and the normal modes that correspond to the lower peaks. Our calculated vibration frequencies are found to be in good agreement with the experimental results observed by Painter et al. (Biopolymers 20 (1981) 243). The method and work presented in this paper may improve Chou's quasi-continuity theory in calculating the vibrational modes of a beta-barrel protein.     

兔脑内Orexin B免疫阳性神经元的分布定位

采用免疫组织化学方法研究了10只青紫蓝兔脑内Orexin B免疫阳性神经元的分布定位。结果显示,Orexin B免疫阳性神经元分布于下丘脑的室旁核、背内侧核、穹隆周核、外侧区和后区以及底丘脑的未定带。以下丘脑背内侧核、穹隆周核和外侧区的阳性神经元数量较多,下丘脑室旁核、后区和未定带较少。表明了兔脑内Orexin B免疫阳性神经元的分布与Orexin A免疫阳性神经元的分布存在一些差异,提示两种Orexin的产生部位和生理功能可能也存在差异。