Changes in dendrites of cortical neurons in experimental alcohol intoxication

Dendrites of cortical neurons were studied in rats in the different stages of alcohol intoxication. Two categories of changes in the dendrites develop under these circumstances: destructive and compensatory. The dynamics of these changes depends on the periods of alcohol intoxication and individual differences in the central nervous system of the animals.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. K. Bogolepov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 1, pp. 87–89, January, 1978.     

IgSF molecule MDGA1 is involved in radial migration and positioning of a subset of cortical upper‐layer neurons

Mdga1, encoding a GPI‐anchored immunoglobulin superfamily molecule containing an MAM domain, is expressed by a specific subset of neurons, including layer II/III projection neurons, in the mouse neocortex. To investigate the function of Mdga1 in corticogenesis, we generated Mdga1‐deficient mice and backcrossed them to obtain a congenic background. Gross anatomy of the Mdga1‐deficient brain at postnatal day (P) 14 showed no obvious phenotype. However, the migration of Mdga1‐mutant neurons to the superficial cortical plate was clearly delayed. Most Mdga1‐mutant neurons reached the lower portion of the upper cortical layer by embryonic day 18.5 and stayed there through P0. By P7, the location of the mutant cells was the same as wild‐type. The location of Cux2‐expressing upper‐layer neurons in the cortical plate was largely unaffected. These observations indicated that Mdga1 is involved in the migration and positioning of a subset of cortical neurons and suggested that the radial migration of upper‐layer neurons might be differentially regulated. Developmental Dynamics, 2011. © 2010 Wiley‐Liss, Inc.     

Structural aspects of cerebral cortical synaptic function in the early postresuscitation period

Department of Histology and Central Research Laboratory, Omsk Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR V. A. Negovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 107, No. 2, pp. 164–166, Febryary, 1989.     

Further observations on vertical bundles of dendrites in the cerebral cortex of the rabbit

Summary In tangential serial paraffin sections through the somatosensory cortex of the rabbit, apical dendrites were traced from the border of layer III/IV to their origin in layer V. From tracings obtained in area parietalis 1 a complete three dimensional reconstruction of several vertical bundles of dendrites was made in a square area measuring about 190×210 m. It was found that (1) The majority of apical dendrites takes part in the formation of vertical bundles. (2) The composition of the bundles changes as they ascend from layer V through layer IV. (3) The apical dendrites of a bundle converge so as to form a neck below a point near the border of layer IV/III where the majority of the dendrites bifurcate into obliquely running branches. (4) In layer IV the bundles are interconnected by dendritic branches of large pyramidal cells the apical shafts of which bifurcate in layer V or deep in layer IV. (5) In addition, an extensive and complicated exchange of fibres running in different bundles through layer IV takes place in layer III.Supported by the Deutsche Forschungsgemeinschaft (Grant Fl 26/13).     

Microinotophoretic study of interaction between cyclic purine nucleotides and mediators on cortical neurons

Statiscally significant evidence of selective interaction between noradrenalin and cyclic AMP and also between acetylcholine and cyclic GMP was found by microiontophoretic application of the cyclic purine nucleotides and mediators to neurons of the rabbit cerebral cortex. These investigations of interrelations of cyclic AMP and cyclic GMP at the single unit level yielded facts suggesting their functional interaction with other systems of intracellular regulators at several different levels.Laboratory of Molecular Neurophysiology and Biochemistry, P. K. Anokhin Research Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR S. S. Debov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 9, pp. 262–265, September, 1979.     

Crawling experience is related to changes in cortical organization during infancy: Evidence from EEG coherence

Greenough's model of experience-expectant plasticity was used to examine EEG coherence among four groups of 8-month-old infants that varied in hands-and-knees crawling experience. Groups included prelocomotor infants, novice crawlers with 1–4 weeks experience, infants with 5–8 weeks, and long-term crawlers with 9+ weeks experience. Resting EEG was recorded from frontal, parietal, and occipital sites of both hemispheres. EEG coherence between intrahemispheric sites was computed. Novice crawlers (1–4 weeks) displayed greater coherence than either prelocomotor infants or experienced crawlers. These data suggest that the anticipation and onset of locomotion was related to an overproduction of cortico-cortical connections. Pruning of these overabundant connections may be a source of the decrease in coherence as crawling becomes more routine. © 1996 John Wiley & Sons, Inc.     

Release of γ-aminobutyrate from the external plexiform layer of the rat olfactory bulb: Possible dendritic involvement

There is biochemical, electrophysiological and immunocytochemical evidence which indicates that the granule cell dendrites of the olfactory bulb contain and synthesize y-aminobutyric acid. The possible existence of mechanisms for the uptake and release of [³H]y-aminobutyrate from these dendrites was investigated by using microdissected samples from the external plexiform layer of the rat olfactory bulb. A high affinity uptake system for [³H]γ-aminobutyrate was shown in this tissue preparation which was temperature and sodium dependent and greatly reduced by L-2,4 diaminobutyric acid. The release of exogenously applied [^H]γ-aminobutyrate from the external plexiform layer was determined in vitro and found to be very similar to that observed in the γ-aminobutyrate-containing nerve terminals of the substantia nigra. High molarity potassium and μmolar amounts of veratridine were able to elicit a reproducible release of [³H]γ-aminobutyrate from the external plexiform layer. Both responses were largely calcium dependent. The veratridine effect was completely blocked by tetrodotoxin.These results would favour the view that dendrites of the granule cell neurones take up and release γ-aminobutyrate from dendritic terminals.     

A re-appraisal of the role of layer VI of the visual cortex in the generation of cortical end inhibition

Summary These experiments examine the effect of blockade of layer VI of the cat striate cortex on the length tuning of hypercomplex cells in the overlying layers II, III and IV. It has previously been suggested that local inactivation of layer VI results in the complete loss of length selectivity in all hypercomplex cells in layers II, III and IV above the blocked region, by removal of an inhibitory mechanism within layer IV, driven from layer VI. However, we have found that, using iontophoretic application of the inhibitory substance GABA to block the activity of layer VI, 29% of hypercomplex cells were unaffected by blockade of the underlying layer VI. The predominant effect on hypercomplex cells was a reduction in visual responsiveness, seen in 71% of cells, with responses reduced on average by 43%. In 50% of these cells (35% of the population) this reduction was apparently specific to responses to the optimum bar length; responses to longer stimuli were unaffected. Iontophoretic application of the potent GABA_A analogue muscimol in layer VI showed a similar spectrum of effects on hypercomplex cells. In these cases, however, the cortical blockade was slowly increased to encompass the recorded cell. In each case, any decreases in length selectivity were also the result of a decreased visual responsiveness. Thus, decreases in length selectivity seen when using either GABA or muscimol were almost exclusively the result of decreased responsiveness to the optimal length of bar stimulus, rather than an increase in response to non-optimal, long stimuli. This suggests the loss of a facilitatory influence from layer VI to layer IV, rather than the loss of inhibition.     

Electrophysiological correlates of short-latency afferent inhibition: a combined EEG and TMS study

Cutaneous stimulation produces short-latency afferent inhibition (SAI) of motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS). Since the demonstration of SAI is primarily based on the attenuation of MEPs, its cortical origin is not yet fully understood. In the present study we combined TMS with concurrent electroencephalography (EEG) in order to obtain direct cortical correlates of SAI. TMS-evoked EEG responses and MEPs were analysed with and without preceding electrical stimulation of the index finger cutaneous afferents in ten healthy volunteers. We show that the attenuation of MEPs by cutaneous stimulation has its counterpart in the attenuation of the N100 EEG response. Moreover, the attenuation of the cortical N100 component correlated positively with the strength of SAI, indicating that the transient changes in cortical excitability can be reflected in the amplitude dynamics of MEPs. We hypothesize that the hyperpolarization of the pyramidal cells due to SAI lowers the capacity of TMS to induce the inhibitory current needed to elicit N100, thus leading to its attenuation. We suggest that the observed interaction of two inhibitory processes, SAI and N100, provides further evidence for the cortical origin of SAI. R. Bikmullina and D. Kičić equally contributed to the study.     

Clinic‐based study of plexiform neurofibromas in neurofibromatosis 1

Individuals with neurofibromatosis 1 (NF1) develop both benign and malignant tumors at an increased frequency. One of the most common benign tumors in NF1 is the plexiform neurofibroma. These tumors cause significant morbidity and mortality on account of their propensity to grow and affect adjacent normal tissues. To determine the clinical profile of plexiform neurofibromas in NF1, we conducted a retrospective review of 68 NF1 patients with plexiform neurofibroma. In our series, 44% of tumors were detected by 5 years of age and most were located in the trunk and extremities. Only two patients developed malignant peripheral nerve sheath tumors in their preexisting plexiform neurofibromas. Lastly, we demonstrate that there were no specific clinical features of NF1 associated with the presence of plexiform neurofibroma. These results underscore the importance of careful serial examinations in the evaluation of patients with NF1. Am. J. Med. Genet. 92:132–135, 2000. © 2000 Wiley‐Liss, Inc.     

An electrophysiological study of the medial prefrontal cortical projection to the nucleus of the solitary tract in rat

The medial prefrontal cortex (MPFC) has been described as a visceromotor cortical area, since autonomic effects such as depressor responses may be elicited from this area. The central circuitry which mediates these depressor responses may include a projection from the MPFC to the nucleus of the solitary tract (NTS). Neurones were recorded extracellularly in the MPFC and were tested for antidromic (AD) activation from the NTS. These were all tested for (1) constant spike latency, (2) ability to follow high-frequency stimulation to more than 200 Hz, and (3) where possible, collision of stimulation-evoked spike with spontaneous spike or spikes evoked by iontophoretic application of glutamate. Of the 34 cells studied, all had constant AD latency (30±1 ms, range 16–46 ms); they followed high-frequency stimulation up to 354±19 Hz, and only seven cells were spontaneously active (range 1–19 spikes/s). The threshold stimulation intensity for AD activation was 102±9 A (n=34, range 8–200 A). Depth-threshold curves (n=7) showed minimum-threshold AD activation currents that corresponded to the dorsal and ventral sub-divisions of the NTS. Small shifts in AD latency were found in the depth-threshold curves, suggesting axonal branching. Analysis of recording sites showed that NTS-projecting MPFC neurones were predominantly found in the infralimbic and ventral prelimbic regions of the MPFC. These findings indicate that there is a population of neurones in the MPFC that projects to, and probably terminates within, the NTS. It is possible that this projection may, in part, mediate the cardiovascular response to MPFC stimulation.     

Face recognition in Asperger syndrome: A study on EEG spectral power changes

EEG reactions in emotional face recognition were studied in five participants with Asperger syndrome (AS) and seven control subjects. Control subjects showed a spectral power increase following the stimulus onset in two time-frequency intervals—(1) 150–300 ms in the 1–16 Hz frequency range and (2) 300–650 ms in the 1–8 Hz range. Also, alpha/beta desynchronization occurred 400–1000 ms after the stimulus onset with maximal amplitude in the posterior region. Theta synchronization (4–8 Hz) was weaker in the AS group than in the control group, but beta2 desynchronization was stronger in the AS group. The results were interpreted in terms of automatic and voluntary control of perception.     

Genetic and environmental influences on frontal EEG asymmetry: a twin study

Research suggests that frontal EEG asymmetry (FA) is a relatively stable trait associated with individual differences in dispositional affect (affective style) and liability to mood disorders. If FA is genetically determined, it can potentially serve as an endophenotype in genetic studies of temperament and mood disorders. The purpose of this study was to assess heritability of FA as well as alpha band EEG power measured at different frontal recording sites. Resting EEG data from a population-based sample of 246 young adult female twins including 73 monozygotic (MZ) and 50 dizygotic (DZ) pairs were analyzed using linear structural equation modeling. FA measured at mid-frontal locations (F3 and F4) showed low but significant heritability, suggesting that 27% of the observed variance can be accounted for by genetic factors. There was no evidence for genetic influences on FA measured at lateral-frontal (F7 and F8) locations. In contrast, alpha band power was highly heritable at all four frontal sites (85-87%). These findings suggest that: (1) genetic influences on FA are very modest and therefore FA has a limited utility as an endophenotype for genetic studies of mood disorders and (2) prefrontal neural circuitry underlying individual differences in affective style is characterized by high developmental plasticity.     

Consequences of altered cerebellar input for the cortical regulation of motor coordination, as reflected in EEG potentials

The cerebellum is certainly involved in fine coordination of movements, but has no efferences of its own to the muscles. Thus, it can exert its influence only via other cerebral areas that have those efferences. This study investigated in patients with cerebellar atrophy how cortical motor areas are affected by dysfunction of the cerebellum. The main question was whether the patients’ slow cortical electroencephalogram (EEG) potentials during key-press preparation and execution would be generally altered or would be specifically altered when fine coordination was needed. In the coordination task, right- and left-hand keys had to be pressed simultaneously with different forces, under visual feedback. Control tasks were to press with both hands equally or with one hand only. The patients indeed had a performance deficit in the coordination task. Their cortical EEG potentials were already drastically reduced in the simple tasks, but were enhanced by the same amount as in healthy subjects when more coordination was needed. These results suggest that the cerebellum is not exclusively active in fine coordination, but is generally involved in any kind of preparatory and executive activity, whereas the motor cortex becomes more active with fine coordination. The role of the cerebellum might be to provide the motor cortex with information needed for coordinating movements. In cerebellar atrophy, this altered input may be sufficient for the motor cortex in controlling simple tasks, but not for complex ones. Received: 4 November 1998 / Accepted: 14 April 1999     

脑梗死患者的脑电图变化与有关因素——阳性诊断标准研究

目的：探讨脑梗死患者脑电图（ＥＥＧ）改变与有关因素的关系。方法：用ＥＥＧ阳性诊断标准对２３７例脑梗死（ＣＩ）和１４７例腔隙梗死（ＬＩ）患者的脑波进行分析,结果：ＣＩ组在发病４周内ＥＥＧ阳性率显著高于１月后（Ｐ＜００１）,而ＬＩ组则无统计学意义（Ｐ＞００５）。ＣＩ组阳性率（６５％）显著高于ＬＩ组（２１８％,Ｐ＜００１）。ＥＥＧ阳性与病初意识障碍或精神症状有关,然而ＥＥＧ阳性率与病变部位或瘫痪程度有关仅见于ＣＩ组。结论：阳性诊断标准能反映卒中后ＥＥＧ变化特征。