Unit responses of the cat lateral geniculate bodies to visceral and somatic stimulation

Acute experiments on cats anesthetized with pentobarbital and immobilized with Diplacin or Listhenon showed that electrical stimulation of the vagus, splanchnic, pelvic, and sciatic nerves and also of the mesencephalic reticular formation induces either a prolonged change in the frequency of unit activity or phasic responses of single units of the lateral geniculate body. During stimulation of the visceral nerves tonic changes in unit activity were predominant, whereas phasic responses were found more often during somatic stimulation. Most neurons tested responded to all types of stimulation used and only 15–18% responded only to the specific stimulus: photic stimulation of the receptive field. The results suggest that interaction of visceral, somatic, and sensory-specific excitation takes place on single neurons of the lateral geniculate body.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Ivano-Frankovsk Medical Institute. Translated from Neirofiziologiya, Vol. 5, No. 3, pp. 246–252, May–June, 1973.     

Changes in neuronal responses of area 7 of cat cerebral cortex to unconditioned and conditioned stimulation under the effects of external stimuli

The effects of external stimuli (ES) and feeding motivations on area-7 neuronal impulse responses (IR) elicited by unconditioned and conditioned stimulation in alert cats were investigated. In untrained cats, preliminary (by 1 sec) action of ES resulted in the disappearance of impulse responses to electrical stimulation of the forepaw (EFS) in the first (no more than five-eight) executions; the responses gradually reappeared and in subsequent executions reestablished their former magnitude. The emergence of feeding motivation excitation in the cats, elicited by food presentation, also promoted disappearance of the initial responses to EFS; these were reestablished only after the cats were quieted. In conditioned-reflex cats, the action of the ES, which had been suppressed after onset of the reflex, as well as lowering of initial feeding motivation level (caused by natural satiation of the cats or by change in quality of the reinforcing food item), led to increase in latent periods (by 50–250 msec) and prolongation of neuronal responses to the conditioning stimulus (CS); but these parameters were unchanged during performance of trained movements. Neuronal response lag time to the action of the CS was defined by ES delivery time and by level of feeding excitation in the cats. The reason for the variation of neuronal responses to unconditioned and conditioned stimulation in the parietal cortex is assumed to be associated with variation in exteroreceptive attention level of cats under the effects of stimuli and altered metabolism.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 564–574, September–October, 1991.     

Synaptic responses of medulla oblongata neurons to stimulation of the spinal stepping atria in the cat

Synaptic responses of medulla oblongata (bulbar) neurons to microstimulation of stepping points in the spinal dorsolateral funiculi were recorded in decrebrate cats. Upon stimulation of the stepping point both in the ipsi- and contralateral funiculi, 40% of the neurons generated synaptic responses; the remaining cells responded to stimulation of only one stepping point. A part of the bulbar neurons responds to stimulation of stepping points both at the C₂ and Th₁₂ level. The latent periods of the synaptic responses of the bulbar neurons to stimulation of the stepping point at the C₂ level were in the 2–10 msec range. The data obtained indicate that bulbar neurons, along with propriospinal neurons, can participate in evoking locomotion upon stimulating the stepping point.Institute of Information Transmission Problems, Academy of Sciences of the USSR, Moscow. M. V. Lomonosov State University, Moscow. Translated from Neirofiziologiya, Vol. 23, No. 3, pp. 328–333, May–June, 1991.     

Response properties of cat AMLS neurons to optic flow stimuli

Spiral and translation stimuli were used to investigate the response properties of cat AMLS (anteromedial lateral suprasylvian area) neurons to optic flow. The overwhelming majority of cells could be significantly excited by the two modes of stimuli and most responsive cells displayed obvious direction selectivity. It is the first time to find a visual area in mammalian brain preferring rotation stimuli. Two representative hypotheses are discussed here on the neural mechanism of optic flow analysis in visual cortex, and some new viewpoints are proposed to explain the experimental results.     

Somatosensory cortical unit responses in the waking cat to afferent stimuli

Extracellular and intracellular responses of 183 neurons in the primary projection area of the somatosensory cortex to electrical and tactile stimulation of the skin on the contralateral fore limb and to stimulation of the ventro-posterolateral thalamic nucleus of the ipsilateral hemisphere were studied in chronic experiments on cats. Spike responses to afferent stimuli are subdivided into three types: initial with a latent period of under 60 msec; initial followed by late responses with a latent period of over 60 msec; late with a latent period of over 60 msec. In addition another group of neurons responding to peripheral stimuli in the interval between the initial and the late response was identified. In nearly all cases the initial responses to peripheral stimulation had the form of a series of spikes, unlike responses to thalamic stimulation. It is concluded from the durations of the latent periods of these responses that about 70% of neurons in the primary projection area are activated mono- and disynaptically in response to peripheral stimulation; consequently, the intracortical spread of excitation in this zone is restricted.     

The late excitatory responses of the motor cortex neurons in the cat to stimulation of the pyramidal tract

Under conditions of partial suppression of GAMKA-dependent cortical inhibition in the motor cortex of anesthetized cats, a weak electrical stimulation of the pyramidal tract evoked the late slow (50-200 ms) excitatory reactions in the motor cortex neurons similar to those previously recorded under the same conditions in response to stimulation of the parietal cortex. This finding favors the proposal that the late excitatory component of the cortico-cortical response reflects the repetitive activation of cortical neurons due to excitation spread via the system of cortical recurrent excitatory collaterals.     

Tuning for cruciform stimuli in visual cortex neurons of cat

In the primary visual cortex of an immobilized awake cat, nearly one-third of the neurons studied (8 out of 22) were found to respond to flashing cruciform light stimuli 1.5–4 times better than to single stimulations with the strips of preferred orientation. It is suggested that such neurons can detect angles and line intersections.Neirofiziologiya/Neurophysiology, Vol. 25, No. 5, pp. 362–364, September–October, 1993.     

Effects of stimulus parameters on cardiovascular responses to medullary stimulation in the cat

The results of this study indicated that when stimulus intensity, pulse frequency and train duration were varied the basic topography of the cardiovascular responses to medullary stimulation did not change, but was merely increased or diminished in magnitude. Pressor responses were usually obtained in conscious cats, and also narcosis produced reversal effect on rare occasions. It is suggested that the reversal in cardiovascular responses is probably locus specific, and the medullary loci yielding reversal effect are more limited than those eliciting consequently pressor responses.     

Effects of ketamine on neuronal epileptiform responses in the cat neocortex

The effects of ketamine, an antagonist of NMDA receptors, on the neuronal epileptiform responses evoked by applications of strychnine, penicillin, or bicuculline to the suprasylvian gyrus were studied in cats. Ketamine either exerted no effect, or slightly decreased interictal high-amplitude depolarizing shifts of the membrane potential and depolarizing afterpotentials, which appeared spontaneously or were evoked by intracortical stimulation. Repetitive electrical stimulation of the epileptogenic cortical regions resulted in the appearance of autogenerated ictal activity lasting up to several tens of seconds; this activity was produced against the background of a depolarization of neuronal membranes. After ketamine injections, such stimulations evoked no ictal activity in the neurons, or the discharges became much shorter. The results of our study show that the NMDA-dependent postsynaptic components play a more important role in the development of neocortical ictal activity compared with the interictal activity.Neirofiziologiya/Neurophysiology, Vol. 27, No. 1, pp. 32–35, January–February, 1995.     

Effect of psychostimulants on responses of neocortical neurons to afferent and subcortical stimuli

The effect of psychostimulants on unit responses of the pericruciate region of the cortex during sensory and subcortical stimulation was studied in experiments on 52 immobilized cats. Amphetamine (2 mg/kg) caused a definite increase in the number of spontaneously active cortical cells. Caffeine (40 mg/kg) had a weaker action. After administration of psychostimulants afferent stimuli more often induced tonic changes in the spontaneous unit activity. More polymodal neurons were found. Phasic responses were often facilitated but were recorded at the same frequency as in the control. Amphetamine and caffeine weakened inhibition of the unit discharges during stimulation of the caudate nucleus and potentiated activation caused by stimulation of the reticular formation. The character of interaction between sensory and reticular (caudate) stimuli was not modulated by the psychostimulants although its scale and intensity were varied. The possible role of the effects of amphetamine and caffeine in therapeutic psychostimulation is discussed.     

Reticular structures in the cat brain involved in startle reflexes to somatic stimuli of various modalities

Characteristics and reticular mechanisms of two types of late reflex responses, namely startle reflexes evoked by weak (tactile) and strong (high-threshold electrical stimulation of nerves) stimulation, were studied in cats anesthetized with chloralose. The peripheral and central organization of these responses, described as "tactile" and "spino-bulbo-spinal" reflexes, were subjected to comparative analysis. Definite rostro-caudal differentiation of the reticular structures involved in the formation of reflexes of these types was discovered with the aid of destructive lesions of the brain-stem reticular formation (RF). Reflexes of the first type relay mainly at the level of the pontine RF, whereas those of the second type relay mainly at the level of the medullary RF. This result was confirmed by reversible blockade of RF by injection of small doses of sodium chloride and procaine solutions into it. The functional significance of this differentiation of RF is discussed in the context of its motor and sensory functions.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 380–390, May–June, 1985.     

缰核痛相关神经元对伤害性刺激和吗啡的反应

目的:观察缰核痛相关神经元对经典镇痛药吗啡的反应,了解缰核的痛觉属性.方法:实验在浅麻醉下的成年大鼠进行.通过脑室插管微量注射,或经五管微电极电泳吗啡、纳络酮、八肽胆囊收缩素(CCK-8)等,并记录缰核内痛相关神经元的单位放电.结果:在内侧缰核、外侧缰核记录的痛相关神经元放电,又可分为痛兴奋性神经元和痛抑制性神经元.在缰核微电泳吗啡后,痛兴奋性神经元以抑制反应为主,痛抑制性神经元以兴奋反应为主.微电泳纳洛酮可以翻转吗啡对缰核的作用.在吗啡耐受大鼠腹腔注射吗啡10 mg/kg,LHb痛相关神经元表现为镇痛效应的数量远大于MHb痛相关神经元的,表明外侧缰核受吗啡的作用程度高于内侧缰核.对吗啡耐受大鼠脑室注入CCK拮抗剂后,再由腹腔注射吗啡,可减弱对吗啡的耐受程度.反之,在腹腔注射吗啡(10 mg/kg)10 min后,侧脑室注射CCK-8(15 ng/10μl),CCK-8可拮抗吗啡对LHb的镇痛作用,但对MHb的拮抗作用不明显.结论:缰核的痛兴奋性神经元和痛抑制性神经元对伤害性(痛)刺激敏感而不易发生适应.其中外侧缰核神经元对吗啡的敏感性高于内侧缰核神经元.     

The responses of auditory ventral-cord neurons ofLocusta migratoria to vibration stimuli

Summary Most of the auditory neurons in the ventral nerve cord ofLocusta migratoria carry information not only from the tympanal organs but also from the subgenual organs (vibration sensors). Six of the eight neuron types studied electrophysiologically respond to at least these two modalities. Artificial sounds (white noise and pure tones varying in frequency and intensity) and sinusoidal vibration (200 Hz with an acceleration of 15.8 cm/s₂ or 2000 Hz and 87 cm/s₂) were used as stimuli.Complex excitatory and/or inhibitory interactions of the signals from both tympanal organs form the discharge patterns of auditory ventral-cord neurons in response to stimulation with air-borne sound. Normally the input of the ipsilateral sense organ dominates. The response patterns of these same neurons elicited by vibration stimuli are formed differently, as follows: (1) the sensory inputs of all subgenual organs are integrated in the responses of the ventral-cord neurons; in a single neuron they have either excitatory or inhibitory effects, but not both. (2) The more legs vibrated, the larger is the response. (3) The subgenual organs in the middle legs are most effective, those in the hind legs least so. (4) Ipsilateral vibration has more effect than contralateral.The six auditory neurons react to vibration combined with air-borne sound in different ways. The B neuron is the only one inhibited by vibration stimuli. The G neuron has been studied more intensively; because its anatomical arrangement and the location of the endings of the subgenual receptor fibers are known, it could be inferred from effects of transection of the connectives that interneurons are interposed between receptor cells and the G neuron.Part of the program Sonderforschungsbereich 114 (Bionach) Bochum, under the auspices of the Deutsche Forschungsgemeinschaft, with the support of the Slovenic Research Society (RSS)     

Effects of food motivation on spike activity of cat somatic cortex neurons

Spike response to unconditioned electrocutaneous stimulation was investigated in cortical neurons of areas 3 and 4 in untrained hungry cats during heightened excitation motivated by food presentation and when at rest. This reinforcement led to changed background activity level, reduced intensity of the initial stages of spike response, and disappearance of late neuronal response. Neuronal response of the same cortical area to a conditioned stimulus (a clicking sound) during reduced food motivation (the animals being sated during the course of the experiment) was also studied under the effects of instrumental feeding reflex. Coordination between the timing of neuronal response and their corresponding movements was discovered from comparing response pattern accompanying the execution of paw-placing (conditioned reflex and intersignal) movements and those recorded at different levels of food-induced excitation, as well as a similarity between these reactions. It was found that the initial stages of neuronal response to a conditioned signal only occurred during contraction of the brachial biceps muscle, while coordination between their timing and that of EMG changes was dependent on the animal's degree of satiation. Findings indicate the possibility of food-induced excitation substantially influencing spike response pattern in somatic cortex neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 725–735, November–December, 1987.