Characteristics of the late A-response of vasoconstrictor neurons in cats decerebrated at different brain stem levels]

In cats decerebrated at the level of the rostral border of the midbrain (the mesencephalic animals) and in those decerebrated at different pontine levels, including the ponto-bulbar junction level, and the most rostral parts of the medulla oblongata (the "pontine" animals), or more caudal parts (the bulbar animals), single stimulus of the tibial nerve A-fibres elicited a late response in the renal nerve consisting of excitatory and inhibitory components. The excitatory component was relatively small or absent in 53% of the "pontine" animals, in 42% of the mesencephalic animals, and in 18% of the bulbar animals. The "pontine" animals had the most active and most excitable system of the inhibitory component generation. However, the signs of a comparatively more powerful inhibitory component of the A-afferent action of the vasoconstrictor neurones in the "pontine" animals were not as constant as to explain completely the transition of somatic A-afferent hypertensive reflexes into the hypotensive ones, occurring in separating the ponto-bulbar structure and the rostral parts of the medulla oblongata from the mesencephalon.     

Model of generation and propagation of impulses in neurons]

A model for the generation and propagation of impulses in nervous tissues was developed. The dynamic properties of the model were studied by analytic and quantitative-analytical methods.     

Responses of somatic cortical neurons during the conditioned placing reflex in cats

Unit activity was studied in areas 3 and 4 during the conditioned placing reflex in cats. Responses of somatic cortical neurons in this case were shown to develop comparatively late — 80–100 or, more often, 200–450 msec after the conditioned stimulus. In the motor cortex responses preceded movement by 50–550 msec, whereas in the somatosensory cortex they usually began simultaneously with or after the beginning of the movement. Judging from responses of somatic cortical neurons, the placing reflex is realized by the same neuronal mechanism as the corresponding voluntary movement. The differential stimulus and positive conditioned stimulus, after extinction of the conditioned placing reflex, evoked short-latency spike responses lasting 250–350 msec in the same neurons as took part in the reflex itself. In these types of internal inhibition, responses of the neurons were thus initially excitatory in character. Participation of the neurons in the conditioned placing reflex and its extinction, disinhibition, and differentiation, is the result of a change in the time course of excitatory processes and is evidently connected with differential changes in the efficiency of the various synaptic inputs of the neuron.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 392–401, July–August, 1982.     

Patterns of early and late discharges in somatotopically identified precentral neurons in awake monkeys in response to somatic inputs.

Extracellular recordings were made of single neurons in precentral cortex of awake monkeys. These neurons were somatotopically identified with respect to their responses to inputs from single joints or their somatic surround. Many of these neurons exhibited early (less than 50 ms) and late (greater than 50 ms) discharges in response to flexion or extension torques delivered about the wrist. With the monkey in a mode requiring opposition to the injected torque, all responsive neurons showed a parallel excitatory or inhibitory modification in the early and late discharges. This was true both for cells identified as wrist (flexion-extension) neurons and those identified as nonwrist (flexion-extension) neurons. These findings indicate that the reflex and voluntary components of percentral discharge invariably show a congruent functional response to a torque disturbance, for this particular instruction set.     

Brain science: from the very small to the very large

We still lack a clear understanding of how brain imaging signals relate to neuronal activity. Recent work shows that the simultaneous activity of neuronal ensembles strongly correlates with local field potentials and imaging measurements.     

Predicting the genome response of the somatic cells of divers to hyperoxic medium]

Cytogenetical consequences of high oxygen pressure action (HOB) have been studied in professional and nonprofessional divers after deepening. Blood samples of subject from both groups were treated with HBO in vitro to compare individual reaction of the somatic cells genome to HOB. The present study reveals that HBO increases the level of chromosome aberrations, and individual response to HBO differs. There is a correlation between the level of chromosome aberrations in vivo and in vitro. This indicates that blood treatment in vitro can reveal the sensitivity of the genome in human before HBO treatment. According to the data in vitro 2 groups of the genome response to HBO: up to 20% and higher than 20% aberrations are distinguished.     

Influence of food motivation on neuronal response of the cat somatic cortex during instrumental reflex

Spike activity in neurons of areas 3 and 4 was investigated in experiments on cats during the conditioned reflex response of placing the paw on a support both before and after feeding ad libitum. Ingestion of a feed consisting of a rapidly absorbed glucose dairy mix did not prevent the reflex taking place if the animals' favorite food was used as reinforcement. Background activity increased in two-thirds of the neurons after the feed; the tonic constituent of neuronal response declined substantially and repeated contraction of the biceps occurring at the same rate as locomotor movements disappeared. Difference in latency of response produced by the conditioned stimulus in the same neurons before and after feeding measured 50–300 msec during the experiment. Measurements of latency of placing motion remained largely unchanged. Changes in the latency of neuronal spike response were thus found to be interrelated with the intensity of the animal's motivational excitation. It is suggested that fluctuations in degree of food motivation lead to changes in cortico-subcortical relationships responsible for initiation and performance of conditioned movements in these animals.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 646–653, September–October, 1987.     

Swallowing reflex and brain stem neurons activated by superior laryngeal nerve stimulation in the mouse

The purpose of the present study was to identify vagal subnuclei that participate in reflex swallowing in response to electrical stimulation of the left superior laryngeal nerve (SLN). SLN stimulation at 10 Hz evoked primary peristalsis, including oropharyngeal and esophageal peristalsis, and LES relaxation. It also induced c-fos expression in interneurons in the interstitial (SolI), intermediate (SolIM), central (SolCe), dorsomedial (SolDM) and commissural (SolC) solitary subnuclei. Neurons in parvicellular reticular nucleus (PCRt) and area postrema (AP) and motoneurons in the semicompact (NAsc), loose (NAl), and compact (NAc) formations of the nucleus ambiguus and both rostral (DMVr) and caudal (DMVc) parts of the dorsal motor nucleus of vagus were also activated. The activated neurons represent all neurons concerned with afferent SLN-mediated reflexes, including the swallowing-related neurons. SLN stimulation at 5 Hz elicited oropharyngeal and LES but not esophageal responses and evoked c-fos expression in neurons in SolI, SolIM, SolDM, PCRt, AP, NAsc, NAl, and DMVc but not in SolCe, NAc, or DMVr. These data are consistent with the role of SolI, SolIM, SolDM, NAsc, NAl, and DMVc circuit in oropharyngeal peristalsis and LES relaxation and SolCe, NAc, DMVc, and DMVr in esophageal peristalsis and LES responses.     

Brain stem insufficiency in acute ischemia and cerebral hemorrhage]

Consciousness disorders are closely related to the general dysfunction of the brain stem, and called by some authors brain stem insufficiency. To evaluate the degree of brain stem dysfunction, an original scale has been elaborated. Each group of brain stem functions are scored. Consciousness being the most important symptom of the brain stem insufficiency is scored about 50% in a 63-score scale. Scores are used to achieve the most objectivity in the clinical monitoring of the brain stem insufficiency. Its utility was examined in 75 patients with either ischemia or cerebral hemorrhage. Patients of both groups with severe insufficiency below 33 scores and persisting over 24 hours had no chance to survive. The authors suggest that the scores may successfully be used in the clinical monitoring of all disorders producing consciousness disturbances. Survival of patients with brain stem insufficiency in the course of cerebral ischemia or hemorrhage depends on the degree and duration of the brain stem insufficiency.     

The modulation of the pulse activity of neocortical neurons during a conditioned reflex]

Spontaneous and evoked activity of neurons in the sensorimotor cortex was recorded in cats with learned conditioned placing reaction before, during, and after the iontophoretic application of synaptically active substances. It was shown that apart from direct excitatory effect on the cortical neurons during its application, glutamate (Glu) exerted some modulatory influence on unit activity in subsequent 20 min. Noradrenaline suppressed the background and evoked activity through beta 1 adrenoreceptors. Activation of beta 2 adrenoreceptors by metaproterenol was accompanied by facilitation of the background and evoked activity during application and 10-20 min after. The joint application of Glu and metaproterenol improved facilitation of neuronal responses evoked by conditioned stimuli. Application of levodopa, like Glu, increased the background and evoked activity of many sensorimotor cortical neurons. The joint effect of Glu and levodopa was not substantially more intensive than the changes produced by the isolated application of any of these substances. A nonselective blocker of DA1 and DA2 receptors haloperidol either increased or did not change the background and evoked activity of some cortical neurons. In contrast to isolated application of Glu, simultaneous application of Glu and haloperidol to neocortex suppressed the neuronal responses associated with conditioned movements. The results suggest that the Glu-induced potentiation is substantially realized through molecular mechanisms common for Glu and dopamine, probably, through Gi-proteins. The conclusion is drawn that the adrenergic and dopaminergic inputs to neocortical neurons are involved in the Glu-mediated plastic changes in the cortex during conditioning.