RESUMO
Centre-surround inhibition--the suppression of activity of neighbouring cells by a central group of neurons--is a fundamental mechanism that increases contrast in patterned sensory processing. The initial stage of neural processing in olfaction occurs in olfactory bulb glomeruli, but evidence for functional interactions between glomeruli is fragmentary. Here we show that the so-called 'short axon' cells, contrary to their name, send interglomerular axons over long distances to form excitatory synapses with inhibitory periglomerular neurons up to 20-30 glomeruli away. Interglomerular excitation of these periglomerular cells potently inhibits mitral cells and forms an on-centre, off-surround circuit. This interglomerular centre-surround inhibitory network, along with the well-established mitral-granule-mitral inhibitory circuit, forms a serial, two-stage inhibitory circuit that could enhance spatiotemporal responses to odours.
Assuntos
Bulbo Olfatório/fisiologia , Olfato/fisiologia , Animais , Axônios/fisiologia , Sensibilidades de Contraste/fisiologia , Eletrofisiologia , Técnicas In Vitro , Camundongos , Camundongos Transgênicos , Odorantes , Bulbo Olfatório/citologia , RatosRESUMO
Coordination between the urinary bladder (BL) and external urethral sphincter (EUS) is necessary for storage and elimination of urine. In rats interneuronal circuits at two levels of the spinal cord (i.e., L6-S1 and L3-L4) play an important role in this coordination. In the present experiments retrograde trans-synaptic transport of pseudorabies virus (PRV) encoding fluorescent markers (GFP and RFP) was used to trace these circuits. To examine the relative localization of EUS-related and BL-related interneuronal populations we injected PRV-GFP into the EUS and PRV-RFP into the BL wall. The PRV infected populations of spinal interneurons were localized primarily in the dorsal commissure (DCM) of L6/S1 and in a hypothesized lumbar spinal coordinating center (LSCC) in L3/L4 above and lateral to central canal (CC). At both sites colocalization of markers occurred in a substantial number of labeled interneurons indicating concomitant involvement of these double-labelled neurons in the EUS- and BL-circuits and suggesting their role in EUS-BL coordination. Intense GFP or RFP fluorescent was detected in a subpopulation of cells at both sites suggesting that they were infected earlier and therefore likely to represent first order, primary interneurons that directly synapse with output neurons. Larger numbers of weakly fluorescent neurons that likely represent second order interneurons were also identified. Within the population of EUS-related first order interneurons only 3-8 % exhibited positive immunoreaction for an early transcription factor Pax2 specific to GABAergic and glycinergic inhibitory neurons suggesting that the majority of interneurons in DCM and LSCC projecting directly to the EUS motoneurons are excitatory.
RESUMO
Field potentials recorded in the olfactory bulb glomerular layer (GL) are thought to result mainly from activation of mitral and tufted cells. The contribution of juxtaglomerular cells (JG) is unknown. We tested the hypothesis that JG are the main driving force to novel spontaneous glomerular layer field potentials (sGLFPs), which were recorded in rat olfactory bulb slices maintained in an interface chamber. We found that sGLFPs have comparable magnitudes, durations and frequencies both in standard horizontal slices, where all layers with all cell types were present, and in isolated GL slices, where only JG cells were preserved. Hence, the impact of mitral and deep/medium tufted cells to sGLFPs turned out to be minor. Therefore, we propose that the main generators of sGLFPs are JG neurons. We further explored the mechanism of generation of sGLFPs using a neuronal ensemble model comprising all types of cells associated with a single glomerulus. Random orientation and homogenous distribution of dendrites in the glomerular neuropil along with surrounding shell of cell bodies of JG neurons resulted in substantial spatial restriction of the generated field potential. The model predicts that less than 20% of sGLFP can spread from one glomerulus to an adjacent one. The contribution of JG cells to the total field in the center of the glomerulus is estimated as approximately 50% ( approximately 34% periglomerular and approximately 16% external tufted cells), whereas deep/medium tufted cells provide approximately 39% and mitral cells only approximately 10%. Occasionally, some sGLFPs recorded in adjacent or remote glomeruli were cross-correlated, suggesting involvement of interglomerular communication in information coding. These results demonstrate a leading role of JG cells in activation of the main olfactory bulb (MOB) functional modules. Finally, we hypothesize that the GL is not a set of independent modules, but it represents a subsystem in the MOB network, which can perform initial processing of odors.
Assuntos
Potenciais Evocados/fisiologia , Rede Nervosa/fisiologia , Neurônios/fisiologia , Bulbo Olfatório/citologia , 6-Ciano-7-nitroquinoxalina-2,3-diona/farmacologia , Animais , Animais Recém-Nascidos , Bicuculina/farmacologia , Estimulação Elétrica , Potenciais Evocados/efeitos dos fármacos , Potenciais Evocados/efeitos da radiação , Antagonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Antagonistas GABAérgicos/farmacologia , Técnicas In Vitro , Masculino , Modelos Neurológicos , Rede Nervosa/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/efeitos da radiação , Técnicas de Patch-Clamp/métodos , Ratos , Ratos Sprague-Dawley , Tempo de Reação/efeitos dos fármacos , Tempo de Reação/fisiologia , Tempo de Reação/efeitos da radiação , Valina/análogos & derivados , Valina/farmacologiaRESUMO
Luminescence and absorption stains specific for DNA (acridine orange, ethidium bromide), proteins (silver nitrate), and lipids (Sudan III) were used to study the distribution of DNA, proteins, and lipids in sections of the olfactory bulb in rats, studies being performed after fixation of brains with paraformaldehyde. DNA was found to be more abundant in the glomerular cell layer than the mitral cell layer. Higher quantities of DNA were present in the granular layer, located beneath the mitral layer. The characteristics of cell layers in the olfactory bulb were studied in rats aged two days and one month. There were differences between the layers of rats of different ages in terms of the content and distribution of DNA, though there were no differences in the total protein or lipid contents. Glomeruli were immature in two-day-old rats.
Assuntos
DNA/metabolismo , Metabolismo dos Lipídeos , Bulbo Olfatório/metabolismo , Proteínas/metabolismo , Fatores Etários , Animais , Lipídeos/análise , Masculino , Bulbo Olfatório/citologia , Bulbo Olfatório/crescimento & desenvolvimento , Ratos , Ratos Sprague-DawleyRESUMO
Using luminescent and absorption stains, specific for DNA (acridine orange, ethidium bromide), proteins (silver nitrate) and lipids (sudan III), the distribution of these substances was studied in the sections of rat olfactory bulbs, fixed by paraformaldehyde. DNA prevalence was found in glomerular cell layer as compared with the mitral one. Large amount of DNA was detected in granular cell layer, underlying the mitral one. The peculiarities of cellular layers of olfactory bulbs of 2-day-old rats were compared with those ones in 1-month-old animals. In rats of different ages, the differences were found in DNA content and distribution between layers, while no differences were detected in total protein and lipids. In 2-day-old rats glomerular underdevelopment was demonstrated.
Assuntos
DNA/análise , Lipídeos/análise , Bulbo Olfatório/química , Bulbo Olfatório/metabolismo , Proteínas/análise , Fatores Etários , Animais , Bulbo Olfatório/crescimento & desenvolvimento , Ratos , Ratos Sprague-DawleyRESUMO
The background firing activity was recorded extracellularly in experiments on guinea-pig neocortical slices maintained in vitro. The following types of background firing activity were revealed: (i) high regular single spikes (48%), (ii) irregular single spikes (15%), (iii) bursts (7%), (iv) groups (7%), (v) mixed activity where single spikes alternated with bursts or groups (28%). The specific interspike interval distribution and the specific shape of autocorrelogram corresponded to each of these background firing activity types. Furie analysis of autocorrelograms showed periodic components in spike sequences with the maxima at 3, 12, and 28 Hz. When blocking synaptic transmission with 100 mM adenosine, about 70% of the background active cells "fell silent" and the remaining 30% of neurons continued to generate action potentials. The latter seem to be actual spontaneously active neurons, i.e. they were capable of autonomous spike generation. We failed to find any correlation between the type of neuronal firing and the ability of neurons to be spontaneously active. The selective blockade of inhibitory synapses with 100 mM picrotoxine did not practically change the character of background firing activity though the responses to stimulation became epileptic. An important conclusion to emerge from this study is that the background firing activity in cortical slices can include the actual spontaneous discharges related to intrinsic cell properties as well as those concerned with synaptic actions. Furthermore, a small number of spontaneously active neurons seem to be able to synaptically activate twice the number of cells. The inhibitory interneurons did not significantly influence the propagation of excitation with the absence of stimulation.
Assuntos
Córtex Cerebral/fisiologia , Neurônios/fisiologia , Adenosina/farmacologia , Animais , Potenciais Evocados , Cobaias , Técnicas In Vitro , Potenciais da Membrana/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Picrotoxina/farmacologia , Sinapses/efeitos dos fármacos , Sinapses/fisiologia , Fatores de TempoRESUMO
On guinea-pig neocortical slices the spatial organization of dendrites sensitive to excitatory amino acids was studied. Extracellular recording were obtained from the the soma of layer V neurons. Responses of 135 neurons to iontophoretically applied glutamate or aspartate have been analysed. An increased firing rate to somatic and most of dendritic applications were of short latency not exceeding 500 ms. Dendritic applications caused somatic responses with far longer latencies (up to 2-3 s) in 18% of cases. Latencies of responses to excitatory amino acids applied to several dendritic sites of the same neuron had similar values. The greatest reactions were obtained in response to excitatory amino acids imposed to the soma and proximal dendrites. At a distance of 100 microm beyond the soma in the basal region and region and further than 300 microm in the apical region excitatory amino acid applications produced two to three times less intensive somatic response. The area where dendritic activation gave rise to change in neuronal firing was confined to 350 and 800 microm for basal and apical dendrites, respectively. Topography of effective dendritic sites fell into the area corresponding to anatomically known outline of dendritic tree of pyramidal neurons. This fact implies that in our experiments we basically dealt with layer V pyramids. The results obtained suggest that local activation of distal dendrites may elicit spike generation in the soma. Different electrical properties of somatic and dendritic membranes are discussed.
Assuntos
Ácido Aspártico/farmacologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/patologia , Ácido Glutâmico/farmacologia , Animais , Membrana Celular/efeitos dos fármacos , Córtex Cerebral/fisiopatologia , Dendritos/efeitos dos fármacos , Eletrofisiologia , Feminino , Cobaias , Técnicas In Vitro , Iontoforese , Masculino , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Tempo de ReaçãoRESUMO
Discharge patterns were studied in response to iontophoretic application of acetylcholine to the soma and dendrites of 128 neocortical pyramidal neurons of layer V. Extracellular recordings were obtained from slices of the guinea-pig parietal cortex. All responses found were excitatory and were better expressed in spontaneously firing cells than in silent ones. Sensitivity to acetylcholine was approximately the same at somatic and dendritic sites in all the cells. Activation of muscarinic receptors gave rise to firing patterns with equal latencies and intensities when applied to both soma and dendrites. The latter suggests that membrane excitation elicited in dendrites by binding of acetylcholine to muscarinic cholinoreceptors is likely to propagate towards the soma through intracellular biochemical processes. Modulating effect of acetylcholine on output firing patterns, elicited by dendritic application of excitatory amino acids, included shortening of the somatic response latency and increase of response intensity and duration. We propose that, in contrast to glutamatergic excitation, the spread of cholinergic excitation along dendrites involves intra-cellular chemical signalling and results in changing the electrical properties of dendrites all over their length.
Assuntos
Acetilcolina/farmacologia , Dendritos/efeitos dos fármacos , Neocórtex/citologia , Células Piramidais/efeitos dos fármacos , Receptores Muscarínicos/efeitos dos fármacos , Animais , Ácido Aspártico/farmacologia , Fibras Colinérgicas/fisiologia , Dendritos/fisiologia , Ácido Glutâmico/farmacologia , Cobaias , Iontoforese , Potenciais da Membrana , Lobo Parietal/fisiologia , Células Piramidais/fisiologia , Células Piramidais/ultraestrutura , Tempo de Reação , Receptores Muscarínicos/fisiologia , Transmissão SinápticaRESUMO
Cultures of primary neurons or thin brain slices are typically prepared from immature animals. We introduce a method to prepare hippocampal slice cultures from mature rats aged 20-30 days. Mature slice cultures retain hippocampal cytoarchitecture and synaptic connections up to 3 months in vitro. Spontaneous epileptiform activity is rarely observed suggesting long-term retention of normal neuronal excitability and of excitatory and inhibitory synaptic networks. Picrotoxin, a GABAergic Cl(-) channel antagonist, induced characteristic interictal-like bursts that originated in the CA3 region, but not in the CA1 region. These data suggest that mature slice cultures displayed long-term retention of GABAergic inhibitory synapses that effectively suppressed synchronized burst activity via recurrent excitatory synapses of CA3 pyramidal cells. Mature slice cultures lack the reactive synaptogenesis, spontaneous epileptiform activity, and short life span that limit the use of slice cultures isolated from immature rats. Mature slice cultures are anticipated to be a useful addition for the in vitro study of normal and pathological hippocampal function.
Assuntos
Hipocampo/fisiologia , Técnicas de Cultura de Órgãos/métodos , 6-Ciano-7-nitroquinoxalina-2,3-diona/farmacologia , Fatores Etários , Animais , Eletrofisiologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Hipocampo/citologia , Microscopia Eletrônica , Fibras Musgosas Hipocampais/fisiologia , Fibras Musgosas Hipocampais/ultraestrutura , Neuroglia/fisiologia , Neuroglia/ultraestrutura , Neurônios/fisiologia , Neurônios/ultraestrutura , Piperazinas/farmacologia , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
In order to simulate the interaction between synaptic input and intrinsic membrane properties in mammalian central neurons a well-defined current was injected into the neurons through a recording electrode. The stimulus was white noise bandpass filtered at 0.5 and 75 Hz and the power spectra of the responses were calculated. Recordings were obtained from neurons of the neocortex, the hippocampus, the thalamus and the cerebellar cortex. The neurons were either located in newly cut slices from adult guinea pig brains or in 3-10-weeks-old slice cultures from brains of newborn rats. In hippocampal and cortical cells the passive membrane properties dominated the shape of the power spectra. In general, when the average membrane potential was made more positive the power of the response increased. When neurons had active subthreshold responses like delayed rectification, sag-and-hump responses or delayed depolarization there was a depression of the response power at frequencies below 10-20 Hz. The depression was voltage dependent in the same way as the current that produced the active subthreshold response. In thalamic cells with a low-threshold Ca2+ spike (lts) the power of the responses grew in the 3-20-Hz range with hyperpolarization. The spectra of the responses of thalamic neurons had multiple peaks indicating multiple frequencies of resonance. Purkinje cells of the cerebellar cortex have prominent plateau potentials. When these cells were stimulated with the white noise at levels where the plateau potentials could be activated the spectra were dominated by a large peak at the lowest frequencies, i.e., below 5 Hz. Few cells in our data base generated spontaneous membrane potential oscillations. When the current stimulus was injected into such neurons the intrinsic rhythm was unaffected by the input and the power spectrum showed a marked peak at the frequency of the intrinsic oscillations. We conclude that bandpass filtered white noise as simulation of synaptic input is valuable for quantification of how passive and active membrane properties affect synaptic integration. The technique can also provide information on the role of transmitters and modulators in the CNS.
Assuntos
Sistema Nervoso Central/fisiologia , Neurônios/metabolismo , Sinapses/fisiologia , Animais , Sistema Nervoso Central/citologia , Estimulação Elétrica , Feminino , Cobaias , Técnicas In Vitro , Masculino , Potenciais da Membrana/fisiologia , Modelos Biológicos , Dinâmica não Linear , Células Piramidais/fisiologia , RatosRESUMO
The background impulse activity of individual neurons was recorded extracellularly in the cerebral cortex of the cat during the prolonged microionophoretic delivery to these neurons of L-glutamate. Glutamate ionophoresis ensured the transition of the neuron to an elevated, but stable level of activation. An autocorrelation analysis of the trains of impulses showed that in spite of the multiple rise in the average discharge frequency, the type of background impulse activity and the periods of increased and reduced probability of discharges for the most part remained constant. The obtained data indicate that an individual cell is unable to influence substantially the interneurons connected with it, while the type of background activity of a neuron is determined primarily by the level of activation of the cellular ensemble incorporating this neuron.
Assuntos
Córtex Somatossensorial/fisiologia , Animais , Gatos , Potenciais Somatossensoriais Evocados/efeitos dos fármacos , Glutamatos/farmacologia , Ácido Glutâmico , Inibição Neural , Tempo de Reação/fisiologia , Córtex Somatossensorial/efeitos dos fármacosRESUMO
The effects of acetylcholine on the spike discharges of neurons induced by iontophoretic application of excitatory amino acids to the bodies and dendrites of cells were studied in 98 neurons in living slices of guinea pig parietal cortex. Acetylcholine applied microiontophoretically to both the bodies and dendrites facilitated improvements in the parameters of responses induced by dendritic activation, with significant decreases in latent periods and increases in the intensity and duration of responses. Thee effects were stably induced at distances of 300 microm from the body and lasted 1 min after exposure to acetylcholine ended. Responses induced by application of excitatory amino acids directly to the cell body did not change significantly in the presence of acetylcholine regardless of the point on the membrane at which they were applied. It is concluded that the predominant effect of acetylcholine is on the efficiency of dendrosomatic conduction.
Assuntos
Acetilcolina/fisiologia , Dendritos/fisiologia , Aminoácidos Excitatórios/fisiologia , Neurônios/fisiologia , Lobo Parietal/fisiologia , Acetilcolina/administração & dosagem , Animais , Dendritos/efeitos dos fármacos , Potenciais Evocados/fisiologia , Aminoácidos Excitatórios/administração & dosagem , Potenciais Pós-Sinápticos Excitadores/fisiologia , Cobaias , Iontoforese , Técnicas de Cultura de Órgãos , Lobo Parietal/efeitos dos fármacos , Transmissão SinápticaRESUMO
Spike responses of neurons to the microiontophoretic application of acetylcholine to the soma and the dendrites were studied. The somatic and dendritic membranes had virtually equal sensitivity to acetylcholine. Only activatory responses were seen, which were most typical of spontaneously active neurons. Muscarinic activation induced spike responses with equal latent periods and equal intensities on application of acetylcholine to dendrites and the soma. It is suggested that intracellular chemical signaling is involved in the propagation of cholinergic excitation via dendrites.
Assuntos
Acetilcolina/farmacologia , Córtex Cerebral/citologia , Dendritos/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Animais , Córtex Cerebral/efeitos dos fármacos , Potenciais Evocados/efeitos dos fármacos , Espaço Extracelular/fisiologia , Cobaias , Técnicas In Vitro , Iontoforese , Microeletrodos , Agonistas Muscarínicos/farmacologia , Lobo Parietal/citologia , Lobo Parietal/efeitos dos fármacos , Lobo Parietal/fisiologia , Estimulação QuímicaRESUMO
The investigation of the ratio of neuronal cytoplasmic RNA mono- and two-chain sections was performed in thin neocortical slices by means of fluorescent probing. Changes of the relative intensity of Acridine Orange red luminescence indicated a decrease in the quota of monochain sections in the common neuronal RNA pool. In eight hours of superfusion it was authentically less than in the control slices and in the slices which were incubated during four hours. Deep profiles of red fluorescence became plane in the process of incubation. It was suggested that the essential decrease in the red luminescence intensity of cytoplasmic RNA in vitro, observed between four and eight hours, may be conditioned by disintegration of polysomes to monosomes, and this, in its turn, may cause the decrease in ribosomal synthetic activity.
Assuntos
Citoplasma/metabolismo , Neurônios/metabolismo , Lobo Parietal/metabolismo , RNA Ribossômico/metabolismo , Laranja de Acridina , Animais , Química Encefálica , Sobrevivência Celular/fisiologia , Técnicas de Cultura , Citoplasma/química , Cobaias , Medições Luminescentes , Microespectrofotometria , Neurônios/química , Lobo Parietal/química , RNA de Cadeia Dupla/análise , RNA de Cadeia Dupla/metabolismo , RNA Ribossômico/análise , Ribossomos/química , Ribossomos/metabolismo , Fatores de TempoRESUMO
This review is concerned with neurogenesis in the mature mammalian brain with emphasis on cell population renewal in the olfactory bulb (OB). The structural and functional features of the OB are considered along with data on neurotropic viruses and toxic dust penetration into the CNS through the OB. We hypothesize a protective role of neurogenesis in the mature OB. This suggests that normal renewal of cell populations in the OB is an important barrier mechanism protecting the brain from invasion of small amounts of harmful neurotropic agents (ex. viruses and particles of toxic dust), which can cause various neurodegenerative diseases.
Assuntos
Neurônios/fisiologia , Bulbo Olfatório/fisiologia , Animais , Diferenciação Celular/fisiologia , Citoproteção , Poeira , Humanos , Metais , Mucosa Nasal/fisiopatologia , Neurônios/citologia , Bulbo Olfatório/citologia , Bulbo Olfatório/virologia , Condutos Olfatórios/fisiopatologia , Viroses/fisiopatologia , VírusRESUMO
The hippocampal rhythms observed in vivo are the result of a complex interplay between cellular and synaptic properties within the hippocampus, and extra-hippocampal tonic as well as periodic inputs. For the stable rhythm to occur, the hippocampal circuitry should have the potential to oscillate at the specific frequencies. The in vitro studies revealed multiple mechanisms supporting the generation of the theta rhythm, which is the main operational mode of the hippocampus. In the hippocampus and related structures cellular membranes can oscillate at theta rhythm when they are depolarized to near-threshold membrane potentials; membranes are also adjusted to resonate with the external signal applied at theta frequency. Synaptically connected hippocampal network alone can generate theta rhythm when a necessary tonic excitation is provided. Finally, rhythmic inputs in theta range from the septum and entorhinal cortex have a propensity to synchronize oscillations in the whole hippocampal formation and associated structures to operate in a unified mode of activity. Based on the results obtained in slices and slice cultures, the present review shows this multilevel hierarchy, which serves to guarantee easy occurrence and reliable maintenance of the theta rhythm in the hippocampus.
Assuntos
Hipocampo/citologia , Hipocampo/fisiologia , Rede Nervosa/fisiologia , Ritmo Teta , Membrana Celular/fisiologia , Humanos , Células Piramidais/citologia , Células Piramidais/fisiologiaRESUMO
The types and values of statistic dependence between extracellularly recorded background spike activity of cortical neurones and EEG oscillations were studied in chronic experiments on intact alert rabbits. It was shown that the relative number of neurones with discharges significantly connected with EEG slow components, remains practically the same in different functional states of the brain and amounts to about 80%. The mean level of the studied dependence changes following transitions from one state to another:it is lowered during the extinction of orienting reaction and continues to go down during the elaboration of the conditioned reflex.
Assuntos
Córtex Cerebral/fisiologia , Condicionamento Clássico/fisiologia , Eletroencefalografia , Orientação/fisiologia , Reflexo/fisiologia , Animais , Mapeamento Encefálico , Eletrochoque , Extinção Psicológica/fisiologia , Luz , Córtex Motor/fisiologia , Coelhos , Córtex Somatossensorial/fisiologia , Córtex Visual/fisiologiaRESUMO
Elaboration of electro-defensive conditioned reflex to light in rabbits has shown, that the values of summary cross-correlation coefficients between EEG and impulse activity of cortical neurones do not change significantly as compared to the control. In these conditions does not change either the part of the neurones that have a significant correlation of their impulse discharges with any configuration of the EEG wave. During 6--10 days of conditioning there occurs a decrease in the amplitudes of both positive and negative EEG oscillations, connected with unit discharges in the neocortex. An EEG quantum has being recorded, i. e. a depolarization potential, directly connected with the generation of spikes by the studied nervous elements.
Assuntos
Aprendizagem da Esquiva/fisiologia , Córtex Cerebral/fisiologia , Condicionamento Clássico/fisiologia , Animais , Mapeamento Encefálico , Eletroencefalografia , Eletrochoque , Luz , Potenciais da Membrana , Córtex Motor/fisiologia , Coelhos , Córtex Somatossensorial/fisiologia , Córtex Visual/fisiologiaRESUMO
The character of statistic connection between the background spike activity of neurones in the visual and sensorimotor cortical areas was studied in calm awake rabbits and in the course of defensive conditioning to light. The obtained cross-correlation functions showed that in the process of establishment of temporary connection, there was a decline in the correlation level between discharges of neighbouring neurones in both areas and a rise in correlation between discharges of remote neurones, one of which was located in the visual area and the other--in the sensorimotor area.
Assuntos
Córtex Cerebral/fisiologia , Condicionamento Clássico/fisiologia , Animais , Mapeamento Encefálico , Eletroencefalografia , Eletrochoque , Luz , Potenciais da Membrana , Córtex Motor/fisiologia , Coelhos , Córtex Somatossensorial/fisiologia , Córtex Visual/fisiologiaRESUMO
Spike activity of cortical units and EEG on the surface of the cortex near the microelectrode were recorded simultaneously in alert non-immobilized rabbits. The technique of synchronous summation used in the data processing has revealed a statistically significant interrelation between background spike activity of the cortical units and the surface biopotentials. A predominant tendency was revealed toward generation of a spike during the maximal surface-positive deviation of slow biopotentials. The average level of cross-correlation between the spike and slow processes in the background has a magnitude of the order of +/- 10(-2), while individual cross correlation coefficients attain the magnitude of 10-1.