[Plastic changes in responses of chemo- and electro-excitable membranes of a cortical neurons following orthodromal tetanization]. / Plasticheskie izmeneniia otvetov khemo- i élektrovozbudimoi membran korkovogo neirona posle ortodromnoi tetanizatsii.

Orthodromic tetanization produces in the turtle visual cortex two types of reversible plastic changes of electrical responses: facilitation and depression. Posttetanic facilitation is attended with reversible enhancement of evoked postsynaptic potentials and APs; the excitability of the electroexcitable membrane increases: the critical level of depolarization of the evoked spike shifts in the negative direction and its threshold potential decreases. Posttetanic depression is accompanied by a reversible decrease of the amplitude of evoked postsynaptic and spike potentials; the excitability of the electroexcitable membrane decreases: the critical level of depolarization of the evoked spike shifts in the positive direction, and its threshold potential increases. Reversible changes of excitability of the spike generating membrane following tetanization testify to the existence of an active mechanism of spike discharge change.

[Electrophysiologic analysis of the representation of the somatosensory system in the dogfish midbrain tectum]. / Elektrofiziologicheskii analiz predstavitel'stva somatosensornoi sistemy v kryshe srednego mozga akuly.

Evoked responses in the dogfish tectum opticum were studied during electrical stimulation of the spinal cord, its dorsal roots and ramus ophthalmicus of the facial nerve. Recordings were obtained from different depth as well as from different points on the tectum surface. Evoked responses could be detected mainly on the contralateral side of the tectum opticum either as slow positive (spinal cord stimulation) or negative-positive (facial stimulation) waves which were preceeded by one or two fast, probably, presynaptic deflections and followed by a very slow low-amplitude negative wave. The evoked responses possessed the properties of tectal postsynaptic responses, being somatotopically distributed on the surface and reversely represented in the inner part of the tectal lamina. Projections of different inputs were widely overlapped, but specific areas of maximal activity were presented. These findings evidence that the tectum opticum performs a double function: a primary projecting and an integrative centre.

[Changes in cortical neuron input resistance and the stimulation threshold of its electroexcitable membrane by a depolarizing current during the habituation process]. / Izmenenie vkhodnogo soprotivleniia korkovogo neirona i poroga razdrazheniia ego élektrovozbudimoi membrany depoliarizuiushchim tokom v protsesse privykaniia.

The habituation of neurones in the turtle visual cortex is accompanied by changes in their input resistance and in the threshold of stimulation of their electro-excitable membrane by depolarizing current. Input resistance of the neurone during monotoneous stimulation decreases throughout habituation and increases following an alien stimulus. The threshold becomes higher if the current acts as a monotoneous stimulus and gets lower if it acts as an alien stimulus. Input resistance of a habituated neurone and its threshold are restored after alien stimulation and spontaneously--after interruption. These changes are specific to the stimulation, appear during its action, and are reversible. They form postsynaptic mechanisms of habituation.

[Mechanisms of habituation of the electroexcitable membranes of cortical neurons]. / Mekhanizmy privykaniia élektrovozbudimoi membrany korkovogo neirona.

Habituation of the cortical neurone response is attended with change in the membrane excitability generating peak potentials. Excitability of spontaneous AP trigger zones increases non-specifically. This is due to a non-specific depolarization shift of the membrane potential during habituation. Excitability of the trigger zones of AP evoked by a monotonous stimulus, decreases: the depolarization critical level shifts in the positive direction and the threshold potential increases. Excitability of the trigger zones of AP elicited by an extrastimulus, enhances: the depolarization critical level shifts in the negative direction and the threshold potential decreases. Excitability changes of trigger zones of evoked AP during habituation are specific, local, reversible and resulting from changed electrogenic properties of the zones: they are underlying the change in the response of the neurone electrically excitable membrane in the process of habituation.

[On--off impulse activity of carp retina amacrine cells]. / Impul'snaia aktivnost' on--off amakrinovykh kletok setchatki karpa.

Properties of spontaneous and light-evoked spikes of the "on--off" amacrine cells of the carp retina were studied. It was assumed that the dendrites of amacrine cells generated spike potentials and conducted them to the cell body. The data obtained suggest that the dendrites of amacrine cells have many spike-generation zones and that the transient depolarization component of the amacrine response to light is the compound spike consisting of many separate spikes generated in different parts of the dendritic arborization of cells. Possible functional role of dendritic spikes is discussed in respect to morphological properties of the "on--off" amacrine cells of the teleost fish retina.

[Rhythmic activity of central portions of the cat visual analyzer during different forms of behavior]. / Ritmicheskaia aktivnost' tsentral'nykh otdelov zritel'nogo analizatora koshki pri nekotorykh formakh povedeniia.

Synchronized EEG activity of visual cortex and some other parts of the brain was recorded in cats during milk licking. The frequency range, cortico-subcortical topography and some conditions of its appearance and blockade were analyzed. It was found, that this activity consisted of two rhythms with frequencies of 6--9 and 9--15 c/s and was strongly influenced by visual conditions. By come parameters it also differed from EEG of drowsiness and light sleep. Possible mechanisms and localization of pacemakers of this activity was discussed as well as its similarity to human alpha rhythm.

Responses and properties of receptive fields of neurons in the visual projection zone of the pigeon hyperstriatum.

Unit responses in the hyperstriatal region of the pigeon forebrain to the action of various visual stimuli were investigated. Particular attention was paid to the discovery of retinotopic projection in the Wulst region. It was shown that as the electrode was advanced in the caudal direction in the zone of visual projection of the hyperstriatum the receptive fields of the neurons recorded shifted in the opposite direction in the visual field. The receptive fields of neurons of the ventral and dorsal hyperstriatum lie higher in the visual field and are larger in diameter than those of neurons of the accessory hyperstriatum. Unit responses in the visual projection zone of the Wulst depend on the intensity of illumination, size, and speed and direction of movement of the test objects across the receptive field. The functional role of the retino--thalamo--telencephalic system in visual interpretation in birds is discussed and it is suggested that the Wulst region is comparable with the striatal and also with the frontal regions of the mammalian cortex.

[Postsynaptic excitation and inhibition in neurons of the general cortex of turtles during presentation of moving stimuli]. / Postsinapticheskoe vozbuzhdenie i tormozhenie v neironakh obshchei kory cherepakhi pri pred"iavlenii dvizhushchikhsia stimulov.

Reactions to moving stimuli were studied in the turtle general cortex. The evoked potentials, synaptic nature of their components and mechanism of their generation were analysed. The evoked potentials was negative-positive. The negative part consisted of fast negative complexes and a slow negative wave. These negative components reflected EPSP generated in the dendrites of the main cortex neurons. A rhythmical oscillation in the evoked potential started after the initial fast negative complex. The negative waves of this oscillation reflected EPSP and the positive waves, IPSP being generated also in the dendrites of the main cortex neurons. They had probably a recurrent generation mechanism. The positive wave of the evoked potential reflected dendritic IPSP in the main neurons.

[Postsynaptic mechanism of habituation of turtle cortical neurons to moving stimuli]. / Postsinapticheskii mekhanizm privykaniia korkovykh neironov cherepakhi k dvizhushchimsia stimulam

An investigation was made into the change in the amplitude of evoked potentials and intracellular slow potentials of the turtle general cortex units in response to a periodic movement of a monotonous stimulus, a black band, across the visual field. The recorded depression of responses possesses all the properties of habituation. The first presentations of the monotonous stimulus produce a generalized habituation, gradually replaced by a selective habituation to the monotonous stimulus, as the number of stimulations increases. It has been shown that it is possible to disinhibit the amplitudes of the evoked potentials and intracellular slow potentials of cortical neurones to moving black bands which form part of the monotonous stimulus. A conclusion has been drawn that habituation of the turtle cortical units to moving stimuli is due to a postsynaptic mechanism.