[Morphophysiologic study of reticulo-cortical pathways in the rabbit]. / Morfofiziologicheskoe izuchenie retikulo-korkovykh putei u krolikov.

The character of functional connections between the midbrain reticular formation (RF) and the neocortex was studied in rabbits. Unit activity was recorded in sensorimotor cortex by extracellular microelectrode during RF stimulation. Short-latency neuronal reactions were found presumably identified as monosynaptic responses. Results of the studies of anterograde degeneration of myelinic fibers and axonal terminals after electrocoagulation of the RF carried out with the help of electronic microscope allowed to suppose that there were few (less than 0.5 per cent) monosynaptic connections between the RF and the sensorimotor cortex. The main forms of direct connections between these structures were axo-dendritic (situated at the dendritic trunk) and axosomatic synapses at the neurones of the sensorimotor cortex.

[Morphofunctional changes in the synapses of the rabbit sensomotor cortex during the summation reflex]. / Morfofunktsional'nye izmeneniia sinapsov sensomotornoi kory krolika pri summatsionnom reflekse.

Synapses of the sensorimotor cortex were studied during summation reflex in chronic experiments on rabbits. Structural changes in presynaptic and postsynaptic components of axodendritic synapses were revealed which are considered as an increase in the functional activity of the synaptic apparatus. The most pronounced response was observed in the postsynaptic matrix, which consisted in a considerable thickening of postsynaptic membranes in a number of axodendritic synapses. It is assumed that the postsynaptic membrane of axodendritic synapses is one of the earliest links structurally fixing the traces of the obtained information.

[Evoked responses and impulse activity of the neocortex during the startle response following stimulation of the midbrain reticular formation]. / Vyzvannye otvety i impul'snaia aktivnost' neokorteksa vo vremia vzdragivaniia pri stimuliatsii retikuliarnoi formatsii srednego mozga.

The stimulation of the mid-brain reticular formation (RF) by single electrical stimuli caused a reticulo-cortical response (RCR) with 2.5--3 msec latency, composed of early (negative-positive complex) and late components. An interconnection is shown between the neuronal response and the formation of different phases of the surface RCR. The neurones of the upper cortical level took part in the response mainly during the development of the negative RCR phases. The appearance of the early positive potential was accompanied by an increase in the frequency of the background activity in the cells of the lower cortical layers. The neurones with initial inhibitory response to the RF stimulation changed their activity in the period of the early RCR components: a considerable part of neurones in the lower layers reduced their spike activity during the development of the short-latency negative oscillation.

[Ultrastructural changes in rabbit sensomotor cortex synapses following stimulation of the reticular formation]. / Ul'trastrukturnye izmeneniia sinapsov sensomotornoi kory krolika pri razdrazhenii retikuliarnoi formatsii.

Ultrastructural changes in the synapses of sensorimotor cortex caused by short and protracted stimulations of mid-brain reticular formation with single electric pulses were studied in rabbits. The observed submicroscopic shift in synaptic apparatus is regarded as a process of enhancing the activity of the sensorimotor synaptic apparatus with involvement of new interneuronal connections. Structural-functional changes in the synaptic apparatus occured at all levels of the sensorimotor cortex, with the predominance of this process at the upper level (layers I-IV); this is probably due to the greater representation of non-specific afferent endings in the upper cortical layers.

[Transformation of the synaptic apparatus of the rabbit sensorimotor cortex following creation of a polarization dominant]. / Perestroika sinspticheskogo apparata sensomotornoikory krolika pri sozdanii poliarizatsionnoi dominanty.

Ultrastructural transformations of axo-somatic and axo-dendritic synapses of the rabbit sensorimotor cortex were studied during: 1) polarization of the cortical surface with a DC anode and 2) the setting up of a polarization motor dominant. A comparison between the structural characteristics of the examined region of the cerebral cortex of the two groups of animals revealed transformations in the synaptic apparatus, which may be regarded as a result of the formation of a temporary connection: an increase in the number of axo-dendritic synapses with considerably thickened postsynaptic membranes; an increase in the number of axonic terminals with a concentration of synaptic vesicles and mitochondria content. The indicated changes were more pronounced in the deep layers of the sensorimotor cortex.