Correlation between activities of neurons of sensorimotor and visual cortices after forming a hidden focus of excitation (defensive dominanta) in cortical representation of a forelimb in rabbits

The interaction between neurons of sensorimotor and visual cortices was investigated by cross-correlation analysis. In this interaction, we examined the role of sensorimotor neurons responding to light. In rabbits with a hidden focus of excitation, neurons of the sensorimotor cortex responding to light significantly more often formed correlation joints with cells of the visual cortex than neurons not responding to light. On the other hand, neurons of the visual cortex significantly more often formed correlation joints with neurons of the sensorimotor cortex not responding to light.     

Correlated activity of neurons in the sensorimotor cortex of rabbits in the state of defensive dominanta and "animal hypnosis"

A hidden excitation focus (dominanta focus) was produced in the rabbit's CNS by threshold electrical stimulation of the left forelimb with the frequency of 0.5 Hz. As a rule, after the formation of the focus, pairs of neurons with prevailing two-second rhythm in their correlated activity were revealed both in the left and right sensorimotor cortices (with equal probabilities 29.3 and 32.4%, respectively). After "animal hypnosis" induction, the total percent of neuronal pairs with the prevalent dominanta-induced rhythm decreased significantly only in the right hemisphere (21%). After the termination of the "animal hypnosis" state, percent of neuronal pairs in the right cortex with prevailing two-second rhythm significantly increasead if the neurons in a pair were neighboring and decreased if they were remote from each other. Similar changes after the hypnotization were not found in the left cortex. Analysis of correlated activity of neuronal pairs with regard to amplitude characteristics showed that for both the right and left hemispheres, the prevalence of the two-second rhythm was more frequently observed in crosscorrelation histograms constructed regarding discharges of neurons with the lowest spike amplitude (in the right hemisphere) or the lowest and mean amplitudes (in the left hemisphere) selected from multiunit records.     

Responses of rabbit visual cortical neurons to intracortical electrical stimulation

Responses of rabbit visual cortical neurons to single and repetitive intracortical electrical stimulation were investigated. The stimulating electrode was located 0.7–1.2 mm away from the recording electrode. Response thresholds to single stimulation were as a rule 150–180 µA, whereas to series of stimuli they were 30–60 µA. The latent period to the first spike averaged 5–15 msec but the probability of the initial discharge was very low, namely 3–6%. With an increase in current intensity the duration of the initial inhibitory pause was increased in half of the neurons responding to it, whereas in the rest it was unchanged. After presentation of series of stimuli spontaneous activity was enhanced for a short time (4–6 sec). In about half of the cells the same kinds of discharge dynamics were observed in response to repetitive stimulation (frequency 0.25 Hz) as in responses to light, but more neurons with sensitization of discharge and fewer "habituating" neurons took part in responses to electrical stimulation. It is postulated that stimulation of a given point of the visual cortex evokes excitation of a local neuron hypercolumn and inhibition of neighboring cell columns.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 15, No. 4, pp. 412–419, July–August, 1983.     

Time and space distribution of coincident impulses in closed neural circuits in the sensorimotor cortex of the rabbit (the rhythmical defensive dominanta)

In the course of analysis of the conjugate unit activity of simultaneously recorded neurons in the sensorimotor cortex of rabbits, 22 closed neural circuits consisting of 3 or 4 neurons were considered. In the model of the defensive dominanta, 1-3 weeks after imposing rhythmic (2 s) activity to a rabbit, the distribution of coincident impulses was analyzed in real time. It was found out that the events when the coincident impulses of neural pairs were generated with two-second intervals could be shifted in time and space over a closed circuit of neurons in one direction. Two-second intervals between the coincident impulses of the neighboring pairs could be conjugate, i.e. the end of one interval in one pair coincided with the beginning of a two-second interval in the next pair. Conjugate intervals of the neighboring neural pairs could promote a pass-through of the information on the stimulus properties over the closed neuronal circuit, thus completing a full cycle. The longest passes-through lasted from 10 and 12 s. Also, more intricate variants of the information transfer were revealed. Thus, not only passes-through of the two- second intervals between the neuronal pairs were observed, but also, coincident impulses repeatedly occurred with this interval in some of the pairs of the circuits. The longest transitions lasted 16 and 22 s.     

Cortical network activity before behavioral reaction and before its omission in rabbits with defensive dominanta

Defensive dominanta was formed in rabbit CNS. Activity of the cortical neuronal network was investigated in these rabbits in the state of quiet wakefulness and in the intervals between the presentations of testing stimulus (light flashes). Statistical analysis of spike trains revealed some distinctions in neuronal functional organizations in the excitation focus (sensorimotor cortex) and in the visual cortex in the states of quiet wakefulness, before the movement of the paw, and before the omission of the reaction. The evidence of different roles in the network activity of sensorimotor neurons that responded and not responded to light was obtained.     

Comparative analysis of the morphochemical changes in the visual and sensorimotor cortical neurons of rats exposed to taftsin

White rats were treated with a single administration of immunostimulator tuftsin (Thr-Lys-Pro-Arg, in the dose 300 mcg/kg b. w.). By interferometry protein content and concentration and the area of neuron cytoplasm and nucleus were assessed 15 minutes after injection, significant alterations in protein content and cellular area were detected in one type neurons of visual and sensomotor cortex. A possible interrelation is discussed between tuftsin action and the functional activity of neurons, and between the level of their protein metabolism and establishment of emotional and motor response.     

Immunolocalization of TASK-3 (KCNK9) to a subset of cortical neurons in the rat CNS

Tandem pore domain (2P) K channels constitute the most diverse family of K channels and are responsible for background (leak or baseline) K currents. Of the 15 human 2P K channels, TASK-1, TASK-2, and TASK-3 are uniquely sensitive to physiologic pH changes as well as being inhibited by local anesthetics and activated by volatile anesthetics. In this study polyclonal antibodies selective for TASK-3 have been used to localize its expression in the rat central nervous system (CNS). TASK-3 immunostaining was found in rat cortex, hypothalamus, and hippocampus. Double immunofluorescent studies identified a discrete population of TASK-3 expressing neurons scattered throughout cortex. Using immunogold electron microscopy TASK-3 was identified at the cell surface associated with synapses and within the intracellular synthetic compartments. These results provide a more finely detailed picture of TASK-3 expression and indicate a role for TASK-3 in modulating cerebral synaptic transmission and responses to CNS active drugs.     

Dynamics of light intensity detection by visual cortical neurons in cats

The dynamics of the intensity function of 32 neurons in area 17 of the visual cortex to photic stimuli of optimal size, shape, and orientation flashing in the center of the receptive field was studied by the time slices method, with a step of 10 or 20 msec, in unanesthetized, curarized cats. All neurons tested showed instability of their intensity function reflected in characteristics of successive fragments of the response: It changed both in preferred intensity and in width of the intensity range within which the neuron generated an above-threshold response. In 72% of cases the preferred intensity for the neuron changed successively during the 4–200 msec after the beginning of stimulation by 4–36 dB from greater toward lesser brightnesses, but later it changed more rapidly (in 20–60 msec), rising again apparently in a jump. In four cases the response optimum was shifted up the intensity scale from its initial value by 10–20 dB. Analysis showed that the observed effects are the simple result of the shape of the relationship between temporal characteristics of the response (latent period, time taken to reach the maximum, and time of ending of the burst) to photic stimulus intensity. The possible functional role of these effects for dynamic time coding of information on brightness of photic stimuli by visual cortical neurons is discussed.     

Comparative analysis of discharge frequency of right and left sensorimotor cortical neurons in rabbits during tonic immobility

Multiunit activity was recorded in left and right sensorimotor cortex of rabbits in the state of tonic immobility. After the first immobilization session, the discharge frequency changed in 47% cells in the right hemisphere: 30% decreased their frequency, and 17% increased. In the left hemisphere, only 18% cells changed their discharge frequency (13% decreased and 5% increased). Reciprocal changes in discharge frequency could be observed in the neighboring neurons (recorded by the same electrode). Several days later, after the second immobilization session, the interhemispheric difference in the number of neurons, whose activity changed, almost disappeared (21% neurons in the right and 24% neurons in the left hemispheres). The relationship between the number of cortical neurons, which increased and decreased their activities in the state of "hypnosis" also became similar in the right and left hemispheres. A suggestion about the involvement of cortical neurons in organization of the state of "animal hypnosis" was made.     

Responses of visual cortical neurons in cats to local stimulation of the receptive field center of varied intensity

On-responses of primary visual cortical neurons to local photic stimulation of the receptive field center by stimuli of scotopic and mesopic ranges of intensity were investigated in dark-adapted curarized cats. Only phasic excitation (type I) was observed in 16% of cells studied, phasic and prolonged excitation with phasic inhibition between them (type II) was observed in 68%, and prolonged inhibition (type III) alone in 16% of cells. The thresholds of phasic excitation in the neuronal responses lay between 0.7 and 2200 trolands (td) and coincided with thresholds of activation of the cone system, whereas thresholds of prolonged excitation lay within the range 0.02–9 td and coincided with thresholds of rod inputs. Inhibitory effects were manifested as phasic inhibition observed on peristimulus histograms, disturbances of the monotony of the responses versus stimulus intensity curve, and also as prolonged inhibition in on-responses. All inhibitory effects were observed in the mesopic range of intensities (0.7–2200 td) and were connected with functioning of the cones.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 359–366, July–August, 1982.     

Formation of a defensive conditioned reflex to an acoustic stimulus in rabbits after early visual deprivation

The formation of a defensive conditioned reflex to sound has been studied in rabbits raised from birth up to 30 days of life in dark. It was shown that, as compared with control animals of the same age, elaboration of reflex to sound takes place in them in shorter times periods and with less pairings. This corresponds to changes in electrographic manifestations of conditioning: increased amplitude and reduced peak latency of evoked potentials to acoustic stimuli in the auditory and sensorimotor cortical zones. The data obtained testify to enahcned functional activity of the auditory cortex, apparently due to a compensatory enhancement of impulse activity coming from the intact receptors of the auditory apparatus. It has been assumed that the observed functional changes appearing in the cortical end of the signal analyser (auditory zone); in response to sound, following visual deprivation, are a consequence of an early nature training of synaptic structures with regard to perceptionof impulses of acoustic modality.     

Responses of neurons in cat visual cortex with sensitivity to bar and cross-like figure

In the cat primary visual cortex (area 17) the response magnitude and latency were studied in 280 neurons sensitive to bar or cross-like-figure. Under natural conditions half of the studied 195 cells preferred bar (first group) or cross (second group). In the first group responses to both figures were near equal, while in the second one cross evoked much stronger response. Response latencies with the optimal bar in the first group were shorter than in the second group and longer to a cross than to a bar while in the second group they were considerably shorter to a cross than to bar. Under local blockage of GABA-ergic inhibition by microiontophoretic application of bicuculline about one-fourth of 85 neurons generated greater responses and were bar-sensitive irrespective to presence or absence of inhibition. Other neurons were cross-sensitive at least in one of the conditions (with and/or without of inhibition). They responses grew under bicuculline action relatively more than in the first group. Significance of the data obtained for tuning to image features and temporal succession of their detection is discussed.     

Responses of medullary neurons to moving visual stimuli in the common toad

The concept of coded 'command releasing systems' proposes that visually specialized descending tectal (and pretectal) neurons converge on motor pattern generating medullary circuits and release--in goal-specific combination--specific action patterns. Extracellular recordings from medullary neurons of the medial reticular formation of the awake immobilized toad in response to moving visual stimuli revealed the following main results. (i) Properties of medullary neurons were distinguished by location, shape, and size of visual receptive fields (ranging from relatively small to wide), by trigger features of various moving configural stimulus objects (including prey- and predator-selective properties), by tactile sensitivity, and by firing pattern characteristics (sluggish, tonic, warming-up, and cyclic). (ii) Visual receptive fields of medullary neurons and their responses to moving configural objects suggest converging inputs of tectal (and pretectal) descending neurons. (iii) In contrast to tectal monocular 'small-field' neurons, the excitatory visual receptive fields of comparable medullary neurons were larger, ellipsoidally shaped, mostly oriented horizontally, and not topographically mapped in an obvious fashion. Furthermore, configural feature discrimination was sharper. (iv) The observation of multiple properties in most medullary neurons (partly showing combined visual and cutaneous sensitivities) suggests integration of various inputs by these cells, and this is in principle consistent with the concept of command releasing systems. (v) There is evidence for reciprocal tectal/medullary excitatory pathways suitable for premotor warming-up. (vi) Cyclic bursting of many neurons, spontaneously or as a post-stimulus sustaining event, points to a medullary premotor/motor property.     

Responses of medullary neurons to moving visual stimuli in the common toad

Summary Intracellular recording and labeling of cells from the toad's (Bufo bufo spinosus) medulla oblongata in response to moving visual (and tactual) stimuli yield the following results. (i) Various response types characterized by extracellular recording in medullary neurons were also identified intracellularly and thus assigned to properties of medullary cell somata. (ii) Focussing on monocular small-field and cyclic bursting properties, somata of such neurons were recorded most frequently in the medial reticular formation and in the branchiomotor column but less often in the lateral reticular formation. (iii) Visual object disrimination established in pretectal/tectal networks is increased in its acuity in 4 types of medullary small-field neurons. The excitatory and inhibitory inputs to these neurons evoked by moving visual objects suggest special convergence likely to increase the filter properties. (iv) Releasing conditions, temporal pattern, and refractoriness of cyclic bursting neurons resemble membrane characteristics of vertebrate and invertebrate neurons known to play a role in premotor/motor activity. (v) Integrating functions of medullary cells have an anatomical correlate in the extensive arborizations of their dendritic trees; 5 morphological types of medullary neurons have been distinguished.Abbreviations A stripe moving in antiworm configuration - (W) moving in worm configuration - S square - BMC branchiomotor column - EPSP excitatory postsynaptic potential - IPSP inhibitory postsynaptic potential - RetF medullary reticular formation - RF receptive field - M neurons response properties of medullary neurons - T neurons classes of tectal neurons - TH neurons classes of thalamic/pretectal neurons - tr.tb.d. tractus tecto-bulbaris directus - tr.tbs.c. tractus tecto-bulbaris et spinalis cruciatus     

Role of cortical inhibition in heterosensory interaction of neurons of the cat sensorimotor cortex

Background and evoked neuronal activity in the cat sensorimotor cortex was recorded under a-chloralose anesthesia. Pairs of heterogeneous stimuli were applied, spaced at intervals of 0, 100, 200, 300, and 400 msec. A clicking sound, flashing light, and electroshock to the contralateral forepaw were used as stimuli. Partial or complete blockade of response to test stimuli presentations spaced 100–200 msec apart were observed when using stimulation of varying modality. The greatest test response was recorded at interstimulus intervals of 200–300 msec. Intracellular mechanisms of heterosensory interaction were investigated by applying the inhibitory transmitter antagonist picrotoxin microiontophoretically to the test cell to produce local attenuation of inhibitory effects. This substance also reduced the duration of blockage following the conditioning stimulus and the occurrence of peak level test response at a lower interstimulus interval than in the controls. Either a consistent increase in the number of spikes per response at one of the interstimulus intervals or a uniform reinforcement in unit response to several different interstimulus intervals were observed in a proportion of the cells. The contribution of intracortical inhibitory influences to the mechanisms of heterosensory interaction on neurons of the cat sensorimotor cortex is discussed in the light of our findings.A. A. Ukhtomskii Institute of Physiology, A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 19, No. 2, pp. 147–156, March–April, 1987.     

Responses to pulsed light stimuli in a pulmonate slug (Limax pseudoflavus)

The phase changes in the activity rhythm of the pulmonate slug Limax pseudoflavus caused by light pulses (30 min, 10,000 lux) in otherwise dark conditions were recorded using time lapse cinematography and tipping aktographs. From the timing of the pulse relative to an individual activity cycle a phase response curve was constructed. Phase delays occurred when the pulse was administered in the early subjective night and subjective day, phase advances were recorded during the mid and late subjective night.
The effects of two pulses (30 min, 10,000 lux) forming symmetric and asymmetric skeleton photoperiods were also recorded and related to the phase response curve. Both stable and unstable entrained states were found, the condition being dependent upon the relative timing of the two pulses and the previous activity onset. It was also shown that there was a time lag between the light pulse and its expressed phase setting effect. Thus phase setting is not instantaneous as with some insects.     

Responses of secondary sensomotor cortical neurons to electrodermal and acoustic stimulation in waking cats

Unit responses in the second somatosensory cortical projection area (SII) to clicks and electric shocks applied to the contralateral limb were investigated in chronic experiments on cats. In response to specific stimulation for the cortical region studied the discharge frequency of 75% of neurons increased, spontaneous activity of 18% was reduced in frequency or the discharges ceased altogether, and 25% of cells did not respond. In response to "nonspecific" stimulation (clicks) 30% of neurons were activated; the discharge of 25% of cells was inhibited and 45% did not respond. The results of investigation of intersensory convergence of stimuli from different sensory systems showed that a high proportion (55%) of SII neurons give bimodal responses. Another 18% of neurons give a specific response to both adequate and inadequate stimulation. It is suggested that the presence of polysensory convergence of SII neurons and of short pathways for the conduction of sensory information, and also the ability of neurons to acquire polysensory properties during stimulus presentation are evidence of the important role of this cortical region in conditioning.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 453–459, September–October, 1977.