Evoked potentials in the frog medulla to electrical stimulation of the glossopharyngeal nerve

Evoked potentials in the frog medulla to stimulation of the glossopharyngeal nerve appear on the ipsilateral side in a zone of limited area. They are recorded at depths not exceeding 2000 µ. Depending on their form the surface evoked potentials are divided into two groups, negative and positive—negative, differing from each other in their parameters and properties. During insertion of the microelectrode the phase of the negative potential is changed. The principal slow components of the responses reflect postsynaptic processes. The first fast wave of the evoked potential is regarded as the presynaptic component. Differences in the properties of the evoked potential recorded at different points are determined by the neuromorphological heterogeneity of the structures of the primary center.     

Response of respiratory neurons of the medulla oblongata to the septum stimulation in hypoxia

In the oxygen deficiency conditions, we studied influence of irritation of ventral (BNST), lateral (LSN) and medial (MSN) nuclei of the septum on the impulse activity of the bulbar respiratory neurons and on respiration. Phases of hypoxia were the model of experiment. In conditions of normal atmospheric pressure, the electrical stimulation of BNST, LSN and MSN nuclei of the septum exerted inhibiting as well as activating influence with the inhibiting influence prevailing. In difficult conditions of hypoxia (7.5-8 thousand meters) on the reduction of the impulse activity of neurons, stimulation of septum nucleuses induced uncharacteristic reactions of those neurons.     

Representation of the lateral line organs in the skate cerebellum

The representation of the lateral line (LL) organs in the cerebellum was studied in acute experiments on skates. It was concluded from analysis of the origin of the various components of the evoked potential (EP) that the EP to stimulation of the LL nerves consists of a fast negative—positive presynaptic wave and a slower biphasic postsynaptic response. The projection zones of each of the LL nerves coincide in the region of the auriculum and posterior lobe. The existence of two functionally different types of LL representation, exhibited as diffuse and local projections, was demonstrated. Their presence is regarded as providing a basis for the integrative activity of the cerebellar structures connected with mechanical and electrical receptors of the LL.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 192–200, March–April, 1972.     

Behavioural and cardiovascular responses to electrical stimulation of the medulla oblongata of the cat

Effects of stimulation of the nucleus tractus solitarii, the dorsal motor nucleus of the vagus, the nucleus reticularis paramedianus, and the nucleus cuneatus were studied in free-moving cats. Stimulation of the medullary nuclei that are known to be involved in the central nervous control of cardiovascular functions might activate preprogrammed motor responses such as licking and sniffing, and induce complex behavioural response patterns such as sleep or flight reaction. Moreover, both lever-pressing for rewarding brain stimulation, and eating in food deprived cats might be modulated by these stimulations. In a shuttle box the cats showed no tendency toward shuttling during stimulation, except the stimulation of the nucleus reticularis paramedianus which produced aversion. The cardiovascular and respiratory effects varied parallel with the behavioural responses. It is concluded that the medullary nuclei related to visceral functions are capable of affecting somatomotor behaviour either directly on the motor system, or by inducing complex response patterns in which somatomotor and visceral responses are integrated.     

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.     

Evoked potentials to electrical stimulation of the facial nerve in the carp tectum mesencephali

Tectal evoked potentials to stimulation of the facial nerve, containing afferent fibers of nonolfactory chemoreception, in the carp are positive evoked potentials with a latent period of 5 to 25 msec which show no phase shift as the microelectrode is advanced to a depth of 600 µ. Depending on the amplitude and latency of evoked potentials seven active zones differing in one or both parameters were distinguished in the ipsilateral tectum mesencephali. The role of impulses from the medulla in the mechanism of tectal evoked potentials to facial nerve stimulation is proved by differences in latent periods and disappearance of the tectal response (although it is preserved in the primary center) after severance of connections between the two parts of the brain. Descending influences from the tectum on the primary center were found: its extirpation disturbs evoked potential generation in several parts of the medullla, so that they either disappear completely or their parameters are modified.A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 39–46, January–February, 1976.     

Evoked potentials in the parietal cortex in response to stimulation of the posterolateral nucleus of the thalamus in kittens of different ages

In kittens of the first month of postnatal life, studies have been made of the evoked potentials in the parietal cortex elicited by stimulation of the posterior lateral thalamic nuclei. It is suggested that within the first days of life the EPs result mainly from the electrical activity of the deep (V-VI) layers of the cortex. This suggestion is confirmed by a significant increase in the velocity of the rising phase and the decrease of the duration of the EPs in the deep layers in newborn animals, as well as partial inversion of the negative wave of the EP at the level of these layers in 1-week kittens. Total depth of the median layers in 1-week kittens is twice less than that in 1 month old ones. To the end of the 2nd week, the input of the activity of the median layers into total activity increases: the focus of partial inversion of the negative wave of the EPs is translocated upward to the border of layers II-III. In 1-month kittens, the general pattern of the EPs in the parietal cortex is the same as in adult cats.     

The effect of the lateral reticular nucleus of the medulla oblongata on the cerebellar cortex

It was established as a result of a laminar analysis of evoked potentials (EP) in the paramedian lobe of the cerebellum of unanesthetized cats that in response to stimulation of the lateral reticular nucleus (LRN) excitation of granulosa cells develops which is not accompanied by excitation of Purkinje cells. Destruction of the lateral nucleus leads to a considerable decrease in the "diffuse" component of the EP which develop during stimulation of the somatic nerves. The results obtained show that the afferent pathway whose fibers innervate granulosa cells of a special type, which have been previously described, passes through the LRN. These cells have extensive receptive fields and do not directly affect the activity of Purkinje cells. A hypothesis is proposed on the basis of the results obtained and data in the literature that the extensive receptive fields of the LRN cells and of the granulosa cells innervated by them are due to interneuronal connections within the lateral nucleus.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Laboratory on the Use of Mathematical Methods in Biology, Moscow University. Translated from Neirofiziologiya, Vol. 2, No. 6, pp. 581–586, November–December, 1970.     

Evoked potentials during the elaboration of a conditioned reflex to hippocampal stimulation in rats

In experiments on 9 rats, the study of evoked potentials (EPs) of the CA1 field of the dorsal hippocampus to stimulation of its symmetrical part serving as a signal of drinking conditioned reflex (CR) showed that during reflex elaboration, the amplitude of the main EP components significantly decreased; CR did not appear when the population spike (PS) was absent in the hippocampal response. PS always accompanying CR was not specific only of it, it was also recorded at other behavioural reactions. Changes of fascia dentata EPs in the process of CR elaboration to stimulation of its symmetrical part consisted in decrease of the initial negative wave and increase of the positive one. The obtained data point to a significant reconstruction of excitatory and inhibitory inputs to the hippocampus and fascia dentata under the influence of conditioned activity.