[The overlapping in the striatum of the projection areas of corticofugal fibers from the somatosensory and motor regions of the rat cerebral cortex]. / Perekrytie v striatume oblastei okonchanii kortikofugal'nykh volokon iz somatosensornoi i motornoi zon kory mozga krysy.

The Fink-Heimer techniques were used to determine the neostriatal projections from cortical M1 and S1 physiologically identified representations of the forepaw. While corticostriatal fibres from S1 enter dorso-lateral parts of the neostriatum fibres from M1 penetrate the dorsal part of the neostriatum more rostrally. Both fibre groups pass in rostrocaudal direction to the globus pallidum, forming terminals on their way. Most of the fibre terminals of M1 projection are located laterally overlapping the zone of distribution of S1 fibre terminals in the neostriatum. Overlapping terminals of the corticofugal fibres of S1 and M1 in the lateral neostriatum can form a basis for interaction of somatosensory and motor impulses. It may be suggested that the role of the neostriatum in sensory integration is associated with certain features of the corticofugal fibre terminals distribution in it at all levels of development of the central nervous system.

[Connections of the representational area of the distal section of the forelimb in the rat sensorimotor cortex]. / Izuchenie sviazei oblasti predstavitel'stva distal'nogo otdela perednei konechnosti v sensomotornoi kore krysy.

Using horseradish peroxidase, studies have been made on the distribution of retrogradely labeled nervous cells in the sensorimotor cortex of rats. The enzyme was injected into electrophysiologically identified zone of representation of the distal part of the forelimb in areas S2 and S1. It was found that this zone in S2 contains afferent connections mainly from representation of the same extremity in S1 and only a few afferents from other areas of S1, S2 and M1 of the same hemisphere. Single labeled neurones were found in areas S2, S1 and M1 of the contralateral hemisphere. Representation of the forelimb in S1 receives mainly cortical afferents from the same region of S1 and from single cells of homologous zones S2 of the same and S1 of the contralateral hemisphere. Connections from S1 to S2 are more numerous than the opposite ones. In contrast to cats and monkeys, in rats afferent cortical fibers to zone S2 pass not only from the third layer, but also from the fifth and sixth layers of the cortex. It is suggested that during progressive development of the neocortex in mammals, the increase in the degree of separation of neurones (which give origin to corticofugal and cortical connections) among different layers of the cortex takes place.

[Correlation between the ipsi- and contralaterally directed nerve fibers from the C2 zone of the rat cerebral cortex]. / Sootnoshenie mezhdu ipsi- i kontralateral'no napravlennymi nervnymi voloknami iz zony C2 kory mozga krysy.

On frontal sections of the brain of albino rats, by means of peroxidase technique, studies have been made on peculiarities of distribution of cortical nervous fibers from somatosensory zone C2 in fugal and comissural directions. Horseradish peroxidase was administered electrophoretically in the focus of the response to electrical stimulation of the distal part of contralateral forelimb of the animal. The data obtained were compared with the results of the distribution of labeled fibers from other, more lateral and medial zones. Single retrogradely labeled cells in symmetrical (with respect to peroxidase application zones) C2 areas of contralateral hemisphere were found indicating the existence of single comissural connections between these parts of the brain cortex. It was established that among anterogradely labeled fibers emerging from the label zone in the focus of the response, comissural ones constitute 34-44%, whereas among fibers from the same zone outside the response focus their share increases up to 52-55%.

[Reactions of reticular formation neurons in the rat during functional suppression of the cortical representation of the extremity stimulated]. / Reaktsii neironov retikuliarnoi formatsii krys vo vremia funktsional'nogo vykliucheniia korkovogo predstavitel'stva stimuliruemoi konechnosti.

Responses of single neurons of the reticular formation were studied in the unanaesthetized immobilized rats. Local cooling of the cortical sensory representation of the stimulated forepaw evoked reversible changes in the responses of most studied units (60 of 86) in different nuclei of the reticular formation. The responses of 25 cells changed only during stimulation of the paw the sensory cortex of which was cooled. The changes of the other unit responses to the same stimulus were more strong (in 13 neurons) or almost equal (in 22 neurons) to the changes in responses to the stimulation of the another paw the sensory projection of which was not cooled. The data suggest that local alteration of the signal transfer in the cortex changes the conditions for the transfer of the same signal in the reticular formation.

[Effect of local cortical exclusion on evoked potentials in the reticular formation occurring in response to somatosensory stimulation]. / Vliianie lokal'nogo vykliucheniia kory na vyzvannye potentsialy v retikuliarnoi formatsii, voznikaiushchie v otvet na somatosensornoe razdrazhenie.

The evoked potentials in different nuclei of the reticular formation were studied in unanesthetized immobilized rats. Evoked potentials in response to electrical stimulation of the forepaw were registered under normal conditions and during cooling of the somatosensory cortex (S1) in the representation area of one the forepaws. It was found that evoked potentials in the reticular formation change according to the degree of depression of the cortex primary response to the same stimulus during cooling. The peak time of the main negative wave increased from 409-50 ms to 60-80 ms with simultaneous decrease of its amplitude up to complete depression during deep cooling of the cortex. The wave with peak latency 14 ms in the ventral reticular nucleus changed in some manner, but less. Parallel registered evoked potentials in response to the stimulation of another paw were preserved in the same points of the reticular formation without changes or they decreased in their value with preservation of their parameters. Thus, during cooling of the cortex there is a selective change in the reticular formation of that signal, the representation area of which in the cortex is depressed. Obviously, the normal development of both late and early components of reticular evoked potentials to the somatic stimuli requires the inflow of an additional corticofugal signal, formed by transformation of the same signal in the corresponding area of the somatosensory cortex.