Structure of Dependent Relationships Between Neurons in the Sensorimotor Cortex of the Left and Right Hemispheres in Rabbits in Immobilization Catatonia

Dependence in the activity of sensorimotor cortex neurons recorded simultaneously in the left and right hemispheres was detected in rabbits in baseline conditions, during the state of immobilization ("animal hypnosis"), and recovery of animals from this state. In baseline conditions, the total percentage of dependent relationships between close-lying (within 50 microm) neurons in the left hemisphere was significantly smaller than in the right hemisphere and did not change either in the state of immobilization or on recovery from it. The total percentage of dependent relationships between close-lying neurons in the right hemisphere decreased significantly during immobilization and returned to baseline levels on recovery from this state. The percentage of dependent relationships between distant (500 microm) neurons in immobilization, conversely, showed no change in the cortex of the right hemisphere, though it changed significantly in the cortex of the left hemisphere, returning to baseline values when the rabbits recovered from this state. Further analysis showed that this cortical interhemisphere asymmetry was based on the asymmetrical activity of individual neurons and small neuronal populations. Thus, changes in the structure of dependent relationships between neurons in microareas of the cortex of the left and macroareas of the cortex of the right hemisphere could be in different directions, while changes in microareas of the right hemisphere and macroareas of the left hemisphere were synergistic. Thus, asymmetry was detected at different levels of neuronal combinations (neuron pairs, micro- and macrogroups of neurons), which suggests mosaicism in neuron structure, which ultimately leads to overall functional asymmetry in "animal hypnosis." Some changes in the structure of dependent relationships between sensorimotor cortex neurons arising in "animal hypnosis" persisted or even became more marked after recovery of animals from this state.     

Dopaminergic Modulation of Spike Activity in Sensorimotor Cortex Neurons in a Conditioned Reflex

Changes in the spike conditioned reflex reactions of sensorimotor cortex neurons during microion-tophoretic application of agonists and antagonists of glutamatergic and GABAergic transmission and their modulation by dopamine were studied. A paradoxical reaction is described, consisting of facilitation of spike responses evoked by antagonists of ionotropic glutamate transmission, which was blocked by GABA. This is evidence for the active involvement of inhibition in organizing the excitatory responses of neurons in the conditioned reflex. Application of the metabotropic glutamate transmission antagonist MCPG was accompanied by sharp suppression of the baseline and evoked activity of cortical neurons, along with increases in the latency of spike responses and conditioned reflex movement. Dopamine was found to reverse the effect of blocking metabotropic glutamate receptors and to normalize neuron activity, which is evidence for the stabilizing role of dopamine in the functioning of neocortical neurons.Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti, Vol. 54, No. 4, pp. 495–507, July–August, 2004.     

Variability in the Structure of Field 39 of the Lower Parietal Area of the Cortex in the Left and Right Hemispheres of Adult Human Brains

The cytoarchitectonics of field 39 of the lower parietal area of the cortex in the left and right hemispheres were studied in normal individuals and professionally gifted world-famous people. Series of frontal sections were studied, stained by the Nissl cresyl violet method. The profile area of neurons was measured in layers III and V and the distribution of neurons in terms of this property was analyzed. Gifted people showed a significantly greater level of individual variability in the measures recorded here, especially in the right hemisphere, with larger proportions of very small and very large neurons.     

Structural and Functional Characteristics of Neurons in the Sensorimotor Cortex of Rats with Different Resistance to Emotional Stress

Wistar rats behaviorally active in the open field test (resistant to emotional stress) are characterized by polymorphism of neurons in layer V of the sensorimotor cortex and the presence of hyperchromatic cells, which probably determines resistance to emotional stress in these rats. Atrophy of hyperchromatic neurons reflecting transient inhibition of cell activity was noted in Wistar rats subjected to stress. In the sensorimotor cortex of behaviorally passive animals (predisposed to emotional stress) groups of densely packed hyperchromatic cells and pronounced pericellular edema were revealed. In these rats stress caused irreversible changes in cortical neurons and death of some cells. The presence of ischemic cortical neurons in rats subjected to emotional stress suggests that cerebral hypoxia plays a role in structural and functional disorganization of the sensorimotor cortex during emotional stress.     

Ultrastructure of the Sensorimotor Cortex of Pubertal Offspring of Alcoholic Male Rats

The ultrastructure of neurons, astrocytes, and capillaries in the sensorimotor cortex of three-month-old offspring of alcoholic male rats (8 g/kg of 50% alcohol solution daily for four weeks) was studied. Apart from signs of delayed maturation of nerve and glial cell processes, some cortical areas showed destructive changes affecting a proportion of neurons along with elements of compensatory-adaptive processes in some nerve cells. Membrane and myelin-like intranuclear inclusions and changes in the Golgi complex were characteristic features of the damage to populations of cortical neurons. Swelling of astrocytes, deformation of capillaries and changes in their ultrastructure, with accumulation of atypical inclusions in pericapillary astrocyte processes, degraded reciprocal exchange processes between blood and neurons. The possible role of the ischemic-hypoxic factor in delayed changes in the ultrastructure of the sensorimotor cortex in the offspring of alcoholic males is discussed. __________ Translated from Morfologiya, Vol. 126, No. 6, pp. 8–11, November–December, 2004. Director: Academician of the Russian Academy of Medical Sciences N. N. Bogolepov     

Structure of the Sensorimotor Area of the Cerebral Cortex in the Offspring of Alcoholized Rats

Light and electron microscopy and morphometry were used to study the characteristics of the cytoarchitectonics of the sensorimotor cortex and the structures of neurons and their dendrites in 21- and 30-day-old baby rats born to chronically alcoholized females and males. Three categories of morphological changes were identified: signs of delayed maturation of neurons and dendrites, destructive changes to these structures, and signs of repair processes, with dynamics occurring during postnatal ontogenesis. At age three weeks, apart from delayed maturation of neurons and underdevelopment of the dendritic system, there were also spreading destructive changes. Increasing age was associated with increases in repair processes, though destructive changes to neurons persisted, which is evidence for the delayed action of alcohol intoxication of animals on the structural development of the brain in their offspring.     

Linkage of Neuron Spike Activity in the Right and Left Amygdala in Food Motivation and Emotional Tension

Cross-correlation histograms were plotted to study the linkage of spike activity in simultaneously recorded neurons in the central nucleus of the right and left amygdala in rabbits in calm waking, after 24 hours of food deprivation, in satiation, and in emotional tension (on presentation of dogs). Histograms showed peaks displaced from zero in 50–67% of cases. In hunger, many cases (52%) showed pairs in which the first neuron to discharge was in the left amygdala, this being followed by a neuron in the right amygdala (peaks from 10–50 and 130–150 msec). Firing in the opposite order was seen more rarely (36%). On presentation of dogs, there was an increase in the number of cases showing a common input to neurons, along with an increase in the leading role of neurons in the right amygdala (57%), due to increases in inhibitory influences from this area on cells in the left amygdala. The interaction of amygdalar neurons in these states was in most cases at frequencies in the delta range (74%), mainly at 2–4 Hz. __________ Translated from Zhurnal Vysshei Nervnoi Deyatel'nosti imeni I. P. Pavlova, Vol. 55, No. 1, pp. 43–51, January–February, 2005.     

The Effects of an NMDA Receptor Antagonist on Delayed Visual Differentiation in Monkeys and Rearrangements of Neuron Spike Activity in the Visual and Prefrontal Areas of the Cortex

The effects of perfusion of field 17 with the glutamate receptor antagonist 2-amino-5-phosphonovaleric acid (APV) on the characteristics of visual recognition and short-term memory were studied, along with the effects of APV on the responses of neurons in the visual and prefrontal areas of the cortex in rhesus macaques. In the test for delayed visual differentiation of stimuli of different colors, behavioral data were recorded simultaneously with multichannel recordings of the spike activity of single cells in cortical field 17 (directly within the microdialysis zone) and field 8. Multifactor dispersion analysis (ANOVA) showed that APV significantly worsened the behavioral characteristics in monkeys, with significant reductions in the duration of short-term storage of information (by factors of 2–4) and significant increases in the motor response times. These changes in cognitive characteristics induced by APV were accompanied by changes in the spike activity of neurons in the visual and prefrontal areas of the cortex during the sensory analysis and delay stages; changes in spike activity consisted of significant desynchronization. These results show that cognitive dysfunctions consisting of worsening of short-term remembering of information and increases in the duration of motor responses during exposure to APV may be caused by desynchronization of neuron activity in various areas of the cortex, these being involved in neuron ensembles responsible for the mechanisms of short-term memory, in which glutamatergic structures play an important role.     

Linked Spike Activity of Neurons in the Right and Left Lateral Hypothalamus in Conditions of Food Motivation

Cross- and autocorrelation histograms were constructed to investigate the linkage of spike activity from neurons in the right and left lateral hypothalamus, recorded in conditions of restful waking, after 24-h food deprivation, and after satiation. In conditions of hunger, there was a preferred order in which neurons fired in these two hypothalamic regions: a significant majority of cases (59%) showed initial firing by a neuron in the left hypothalamus followed by a neuron in the right, with delays of up to 200 msec and peaks in the delay plot at 30 and 160 msec. The opposite firing order was seen less frequently (21% of cases). In conditions of hunger, linked spike activity showed an increase in the probability of detecting frequencies in the theta range (from 11% to 29%).     

The Possibility of Left Dominant Activation of the Sensorimotor Cortex During Lip Protrusion in Men

Lip protrusion requires bilateral symmetrical movements of the facial muscles, but the laterality of the activated sensorimotor cortex corresponding to the area of the face activated during lip protrusion remains under discussion. In this study, blood-oxygenation-level-dependent (BOLD) responses in the sensorimotor cortex during non-verbal lip protrusion were evaluated in a 3T magnetic field in twenty healthy right-handed subjects. The results showed that the activated sensorimotor area on the left side was larger than that on the right side, and there was a statistically significant difference in the number of activated voxels between the left and right sensorimotor cortex in an individual study of the male group, although approximately symmetrical motor action potentials of facial muscles were recorded during lip protrusion. There was a statistically significant difference in interaction between the hemisphere (right and left) and sex (men and women) and multiple comparison test showed statistical significant differences between “men and right” and “men and left”, and between “men and left” and “women and left”. The peak value of the percent changes in BOLD signal responses on the left side was approximately twice as high as that on the right side in the males of the group, though the bilateral sensorimotor cortex was almost equally activated in the females in the group. In addition, the left primary sensory area related to the face area was significantly activated as a region where Male was more active than Female in a general linear model (multi-study, multisubject) analysis. This study revealed the possibility that the left sensorimotor cortex was more closely involved in non-verbal mouth movement in men, suggesting sex-related differences in sensorimotor cortex activation.     

Characteristics of neuronal responses in the sensorimotor cortex of the cat to monaural and binaural stimulation

The dependence of neuronal responses in the sensorimotor cortex (SMC) of the cat upon localization parameters of dichotically presented auditory signals was studied in acute experiments. Binaural stimulation was more effective than either monaural stimulation. It was shown that spatial-localization parameters of auditory-stimulus source such as interaural differences in intensity and time are reflected by the characteristics of neuronal responses in the SMC; moreover, in 67–88% of cases the most pronounced responses were observed for small, close to zero, temporal and amplitudinal interaural shifts. It was found that SMC neuronal background activity may be altered by signals simulating directed movement of the sound source in the horizontal plane.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 65, No. 6, pp. 801–811, June, 1979.     

Dynamics of Neuron Spike Activity in the Oral Nucleus of the Pons During the Sleep-Waking Cycle in Cats

Chronic experiments on five cats were performed to study the spike activity of neurons in the oral nucleus of the pons during waking, slow-wave sleep, and paradoxical sleep. Groups of neurons with different dynamics of spike frequency were identified. Cells with rare discharges during waking and slow-wave sleep and maximum spike frequencies in the phasic stage of paradoxical sleep were regarded as PS-on neurons. Cells discharging at maximum frequency during waking, with decreases in frequency during slow-wave sleep and further decreases in paradoxical sleep, were regarded as PS-off neurons. Cells showing decreases in discharge frequency on the transition from waking to slow-wave sleep and increases in discharge frequency in paradoxical sleep, with grouped spikes during oculomotor activity, appeared to be responsible for generating the phasic phenomena of paradoxical sleep. The question of the involvement of neurons of different populations in the mechanisms of paradoxical sleep is discussed.     

Comparative Analysis of Neuron Activity in the Prefrontal Cortex of the Rat Brain in the States of Productive and Nonproductive Work

Neuroscience and Behavioral Physiology - The aim of this study was to investigate neuron activity in prefrontal cortex cells in animals in different neuromental states. Spike activity was recorded...     

Use of a Simplified Method of Optical Recording to Identify Foci of Maximal Neuron Activity in the Somatosensory Cortex of White Rats

Eight mongrel white male rats were studied under urethane anesthesia, and neuron activity evoked by mechanical and/or electrical stimulation of the contralateral whiskers was recorded in the primary somatosensory cortex. Recordings were made using a digital USB chamber attached to the printer port of a Pentium 200MMX computer running standard programs. Optical images were obtained in the barrel-field zone using a differential signal, i.e., the difference signal for cortex images in control and experimental animals. The results obtained here showed that subtraction of averaged sequences of frames yielded images consisting of spots reflecting the probable position of activated groups of neurons. The most effective stimulation consisted of natural low-frequency stimulation of the whiskers. The method can be used for preliminary mapping of cortical zones, as it provides for rapid and reproducible testing of the activity of neuron ensembles over large areas of the cortex.     

Hazard Functions and Expected Spike Density Functions for Neuron Spike Activity in the Cochlear Nucleus of the Cat

The goal of these experiments was to evaluate the effect of stimulus evoked input and post spike refractoriness on the shapes of post stimulus time histograms (PSTHs). The time courses of spontaneous and/or evoked activity were studied in 153 neurons located predominantly in the dorsal cochlear nucleus in cats anesthetized with Nembutal. Tone bursts were presented to the ipsilateral ear in a free sound field. About half the cells were characterized by the pauser/build-up type of PSTH. Marked refractoriness was evidenced by relatively long recovery times of the hazard functions of spontaneous and tone-evoked spike activity. On presentation of tonal bursts, the time dependence of the probability of the first spike in the absence of a preceding spike (expected spike density function) was greater than the PSTH (actual spike density function). The initial PSTH peak with pause was shaped primarily by stimulus evoked input, whereas refractoriness tended to diminish the build-up portion of the PSTH. In chopper cells, PSTH peaks were usually not reflected in expected spike density functions showing that post spike refractoriness plays a major role in shaping the PSTH. In primary-like cells, refractoriness was small and had little effect on the shape of the PSTH. Some presumptively inhibitory cells showed a tendency to burst discharges with non-monotonic hazard functions. A very small number of cells showed a tendency to internal tuning to a defined signal periodicity.     

Morphological Characteristics of Lugaro Cells in the Cerebellar Cortex

Two types of Lugaro cells were identified in the cat cerebellar cortex using sections impregnated with silver nitrate by the Golgi-Kopsch method; these cells were fusiform and triangular and their bodies were located at different levels in the granular layer. Their processes were directed horizontally, vertically, or obliquely to the axis of the leaf; axons never left the cerebellar cortex. These cells should therefore be regarded as interneurons. The processes of Lugaro cells were very extended, with the result that these cells formed numerous axosomatic and axodendritic contacts with all cerebellar cortical neurons and fibers. The structural and topographical characteristics of Lugaro cells and the features of their contacts with other cells in the cerebellar cortex, taken together with data on their neurotransmitter contents, show that they function as inhibitory interneurons.     

Long-Term Potentiation and Evoked Spike Responses in the Cingulate Cortex of Freely Mobile Rats

Long-term potentiation of synaptic efficiency is regarded as a major candidate for the role of the physiological mechanism of long-term memory. However, the limited development of concepts of the cellular and subcellular characteristics of the induction of long-term potentiation in animals in conditions of free behavior does not correspond to the importance of this question. The present study was undertaken to determine whether the characteristics of potentiation in the cingulate cortex in response to stimulation of fibers of the subiculo-cingulate tract are truly long-term, i.e., develop through all known phases and last at least 24 h, in freely moving animals. In addition, the study aims included identification of the effects of application of blockers of different types of glutamate receptors on the development of long-term potentiation and identification of the characteristics of spike responses of single cingulate cortex neurons to stimulation of the subiculo-cingulate tract. Long-term potentiation, lasting more than 24 h, was obtained in freely moving adult rats not treated with GABA blockers. Injection of glutamate NMDA synapse blockers led to significant decreases in evoked cingulate cortex potentials in response to test stimulation. Activatory short-latency spike responses were characterized by a low probability of spike generation, and this increased with increases in the stimulation current. These data demonstrated that it is methodologically possible to compare, in freely moving rats, the involvement of individual neurons in the mechanisms involved in learning one or another type of adaptive behavior and the dynamics of their evoked spike activity during the formation of long-term potentiation.