Polarization and spectral sensitivity of single photoreceptors of the domestic cricket

The polarization and spectral sensitivity of single photoreceptors ofAcheta domesticus L. was measured. The morphological characteristics of the cricket rhabdome satisfy the conditions for a symmetrical model, for which the polarization sensitivity of a single photoreceptor is identically equal to the dichroism of a single microvillus. Characteristic curves of spectral sensitivity of all photoreceptors measured (24 cells) were similar and had two maxima: the principal at 500 nm and a secondary peak at 360 nm, characteristic of a pigment such as rhodopsin in the rods of the vertebrate retina. The mean value of polarization sensitivity measured was 2.28 ± 0.85 (mean ± standard deviation, 70 cells), suggesting the existence of slight preferential orientation of the dipole moments of the rhodopsin molecules along the axes of the microvilli.I. N. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Institute of Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 483–490, September–October, 1979.     

Changes in distribution of synaptic vesicles in endings of cones during electrical stimulation of the retina

Conditions (hypoxia) were chosen under which, judging from the reduction in the responses of the horizontal cells to electrical stimulation of the retina, mediator is exhausted in the presynaptic endings of the photoreceptors. Under these circumstances a number of "small" synaptic vesicles were shown to be reduced in those parts of the cones which are in direct contact with presynaptic membranes. No significant changes were found in the total number of "small" vesicles in the cone endings.Institute for Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 8, No. 6, pp. 620–623, November–December, 1976.     

Effect of background illumination on evoked potentials of the visual system in the turtle

We discovered an enhancing effect of background illumination on amplitude and total duration of electrical reactions of the tectum of the midbrain and pallial thickening in response to a flash and electrical stimulation of the optic nerve. This effect is analogous to the phenomenon of photic potentiation known for the visual system of mammals. Changes of evoked potentials in the contralateral pallial thickening and tectum were fairly stable and survived throughout the course of the entire period of illumination (up to 30 min). The effect was intensified with an increase of illumination intensity. Intensification of response on the part of the tectum and pallial thickening during steady illumination was accompanied by a weakening of slow background electrical activity. During the action of background illumination, the excitability of the tectum rose considerably with direct electrical stimulation. The influence of prolonged illumination on responses of the tectum and pallial thickening was more clearly detected at submaximal strengths of stimulation of the optic nerve or tectum. All of the effects of photic potentiation are confined to centers contralateral to the illuminated eye. This indicates the absence of diffuse effects on excitability of the turtle brain.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 1, No. 2, pp. 219–224, September–October, 1969.     

Sensory interaction in the snailHelix lucorum

The activity of hair cells of statocysts inHelix lucorum was investigated by means of intra- and extracellular recording, applying appropriate stimulation of the organs of balance, optic photoreceptors, and the chemoreceptors of the optic tentacle bulb. Mechanical stimulation of the statocysts evoked a firing reaction in the hair cells as a result of generator potentials occurring at the receptors. The amplitude of generator potentials was proportional to the intensity of the reaction. Stimulating the optic photoreceptors by switching on a light produced a spike response in the hair cells with a short latency of 0.3–2 sec. The latent period of this response was inversely proportional to the intensity of the light. Appropriate stimulation of the chemoreceptors of the optic tentacle bulb caused a faint spike response with a long latent period of 20–40 sec in the hair cells. Illumination and stimulation of the chemoreceptors produced an inhibitory response in the form of bursts of IPSP in 2 out of more than 50 hair cells.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 17–26, January–February, 1986.     

Parameters of photic stimulation and characteristics of thermal response in the white rat cerebral cortex

The dynamics of the localized thermal response produced in the cerebral cortex when a retinal photic stimulation pattern is established were studied through the unopened skull during acute experiments on white rats using techniques of thermovision and digital image processing. The relationship was evaluated between amplitude, time course, and spatial characteristics of response on the one hand and stimulus size, position on the retina, focus, duration, quantity, and frequency of presentation on the other. A discussion follows of the properties, significance, and underlying mechanisms of the thermal effects discovered.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 332–340, May–June, 1985.     

Unit activity in the superior colliculus after removal of corticofugal control

Changes in spontaneous and evoked unit activity in the superior colliculus of the cat were studied after unilateral blocking of corticofugal connections. Functional characteristics of the cells were compared in the intact and disconnected colliculus. In neurons on the side of the operation the spontaneous firing rate was reduced and responses to photic stimulation were virtually completely abolished: only 7.1% of collicular cells on the side of the operation responded to adequate stimulation. Effective mechanisms of corticofugal control, modulating the relaying of the efferent volley in the tectal neurons, evidently function in the superior colliculus.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 54–61, January–February, 1978.     

Two types of binocular convergence of visual information in the cat superior colliculus

During binocular stimulation of different sectors of the retina the amplitude of the two first postsynaptic components of the evoked potential in the superior colliculus to the second stimulus varies with the time delay between the testing and conditioning stimuli. Correlation is shown between the form of the evoked potential arising in response to the conditioning stimulus and the character of convergence of visual impluses in the superior colliculus. Qualitative differences are found in binocular interaction between sensory impulses depending on the way in which the conditioning impulses reach the region of the superior colliculus tested. An attempt is made to assess interaction between sensory volleys in the superior colliculus quantitatively.Institute of the Brain, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 2, pp. 133–137, March–April, 1973.     

Two types of lateral inhibition in the frog retina

Two independent types of lateral inhibition were distinguished in experiments on the frog eye in which the effects of pharmacological agents on the electroretinogram were studied: proximal or picrotoxin-sensitive, and distal or strychnine-sensitive. Distal lateral inhibition (at distances up to 1.5 mm) is the familiar type already well investigated and based on a spike mechanism of transmission of the inhibitory signal. The proximal (up to 400 µ) picrotoxin-sensitive inhibition has a different mechanism of transmission, not dependent on spikes. The localization of the two types of lateral inhibition in the synaptic layers of the frog retina is discussed.Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 5, pp. 549–555, September–October, 1981.     

Recovery cycles of mass evoked potentials of different levels of the visual system following electrical stimulation of the optic nerve

Recovery cycles of mass evoked potentials of the optic tract, lateral geniculate body, optic radiation, and primary projection area of the visual cortex were investigated in amytal-anesthetized cats following electrical stimulation of the optic nerve (in some experiments, optic radiation) by paired short stimuli of supraliminal intensity. The recovery of the amplitude and time characteristics of all components of the mass responses to a testing stimulus applied to the nerve at different intervals after an identical conditioning stimulus was studied. The responses of all portions of the visual system (except the retina) were recorded simultaneously, which made it possible to compare the changes of their reactivity arising after the first stimulus under rigorously identical conditions. It was shown that at the upper levels of the visual system the exaltation phase of the recovery cycle and the depression phase following it become increasingly more pronounced and protracted. Depression is especially pronounced in the visual cortex, which maximally affects the recovery of the late components of the mass response. Under the experimental conditions the processes of successive inhibition in the cortex were more pronounced than at the lower levels. There are grounds to assume that the depression of the cortical responses is partially due to pre- and partially postsynaptic inhibition.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 3, pp. 251–259, May–June, 1970.     

Neurophysiological analysis of postnatal development of corticostriate connections in rabbits

Evoked potentials were recorded in the caudate nucleus of adult rabbits and young rabbits aged 2–30 days in response to stimulation of the ipsilateral motor cortex. The response of the caudate nucleus in the adult rabbit consisted of a positive-negative complex with latent period of 3–5 msec. Maximal amplitude of the response was observed in the dorsorostral region of the nucleus. As the recording electrode was inserted deeper, the amplitude of the response gradually decreased but without reversal of its polarity. Responses of the caudate nucleus to stimulation of the motor cortex were recorded as early as on the 3rd day after birth. These responses were indistinguishable in configuration from responses of the nucleus of adult rabbits. Their latent period was about 10 msec. Between the 16th and 20th day after birth the latent period of the response decreased considerably — from 9 to 5 msec, and by the 30th day of life it had reached its definitive value. With age the amplitude of the response increased but the threshold of stimulation decreased, The results indicate early functional maturation of connections of the motor cortex with the caudate nucleus and they agree with the results of morphological investigations of the structural development of the afferent systems of this nucleus.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 284–289, May–June, 1982.     

On the transmission of signals in vertebrate retina in the presence and absence of impulses

The ability to transmit signals in the retina in the absence of impulses was tested by means of two agents (tetrodotoxin and procain) blocking the impulse transmission of stimuli. The slow potential (SP) and impulse discharge were recorded simultaneously from the optic nerve of the frog. Tetrodotoxin (0.5 µg/cm³) and procain (0.5–1%) introduced into the eye cup completely blocked impulses but had little effect on SP. Therefore, signals from the photoreceptors to the ganglionic cells can be transmitted in the absence of impulses. These data confirm also a conclusion drawn earlier that the SP originates as a result of electrotonic spread of the postsynaptic potentials (PSP) of ganglionic cells along the optic nerve. The agents blocking the impulse transmission of stimuli broke down the lateral inhibition between the "slow bipolars." Consequently, lateral inhibition spreads by means of the impulse mechanism in the transmission of signals. It is supposed that the interneurons participating in this spread are amacrine cells which possess the ability to generate impulses.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 5, pp. 536–543, September–October, 1970.     

Investigation of the mechanism of temperature sensitivity of the electroreceptors of ampullae of lorenzini

In experiments on Black Sea skates (Raja clavata), the potential of the receptor epithelium of the ampullae of Lorenzini and spike activity of single nerve fibers connected to them were investigated during electrical and temperature stimulation. Usually the potential within the canal was between 0 and –2 mV, and the input resistance of the ampulla 250–400 k. Heating of the region of the receptor epithelium was accompanied by a negative wave of potential, an increase in input resistance, and inhibition of spike activity. With worsening of the animal's condition the transepithelial potential became positive (up to +10 mV) but the input resistance of the ampulla during stimulation with a positive current was nonlinear in some cases: a regenerative spike of positive polarity appeared in the channel. During heating, the spike response was sometimes reversed in sign. It is suggested that fluctuations of the transepithelial potential and spike responses to temperature stimulation reflect changes in the potential difference on the basal membrane of the receptor cells, which is described by a relationship of the Nernst's or Goldman's equation type.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov, Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Pacific Institute of Oceanology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 67–74, January–February, 1980.     

Peculiarities of synaptic transmission between photoreceptors and horizontal cells

A previously advanced hypothesis, according to which the transmitter which depolarizes the membrane of horizontal cells is continually liberated in the dark, and ceases to be liberated in the light, is tested experimentally. The data presented show that a current acting on presynatic receptor endings evokes a depolarizing response in horizontal cells to short current impulses passing through the retina (anode on receptor surface, cathode in vitreous body). These receptor endings are depolarized, which evidently leads to liberation of the transmitter from the receptors. Experiments with electrical stimulation of the retina have shown that treatment of the retina with potassium cyanide disrupts synaptic transmission between the receptor and horizontal cell. A potential equal to their membrane potential is established in horizontal cells in bright light; this potential is evidently the true rest potential of these cells. The relative stability of the membrane potential of horizontal cells in light with change in temperature is evidence in support of this assumption. In the dark, the membrane potential increases considerably with increase in temperature; this effect is possibly due to a rise in the rate of decomposition of the depolarizing transmitter. Evidence in support of this hypothesis is the rise in steepness of the falling phase of the response of the horizontal cells to electrical stimulation observed on elevation of the temperature.Institute for Problems of Information Transmission of the Academy of Sciences of the USSR, and Institute of Higher Nervous Activity and Neurophysiology of the Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 79–86, January–February, 1970.     

Selectivity in the response of human cerebral neurons to visual stimuli at different angles of alignment

The neuronal activity of different nuclei of the thalamus and striopallidar complex was investigated in Parkinsonian patients with intracerebral electrodes chronically implanted in these structures for diagnostic and therapeutic purposes. Neuronal populations were discovered responding differently to the presentation of stimuli identical in all but angle of presentation, some of which responded solely to a single orientation and might therefore be thought of as displaying directional sensitivity. It is suggested that when motor and visual information converge within the above systems, a matching process takes place, together with an interaction relating to stability of visual perception.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad; Institute of Information and Automotive Sciences, Academy of Sciences of the USSR, Leningrad. Translated from Neirofizologiya, Vol. 19, No. 1, pp. 3–11, January–February, 1987.     

Functional development of hippocampal mossy fiber synapses in rabbits

The course of functional maturation with age of mossy fiber synapses on pyramidal cells in areas CA_3,4 of the dorsal hippocampus was investigated by extracellular recording of focal potentials and single unit responses of the hippocampus to electrical stimulation of the dentate fascia in waking, unimmobilized rabbits aged from 1 to 14 days. After the 4th day of postnatal life focal potentials appeared in response to single stimulation, in the form of a biphasic short-latency wave, characteristic of responses of the mature hippocampus, accompanied by spike discharges with a latent period of 3 to 10 msec and inhibitory responses of the hippocampal neurons. During the next 10 days the amplitude of the focal potentials increased from several hundred millivolts, with the sharpest increase observed from the 4th through the 7th days. In early age periods global and unitary responses were shown to be capable of frequency potentiation and also of short-term after-potentiation.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 3, pp. 246–254, May–June, 1980.     

Effect of strychninization of the rabbit visual cortex on evoked activity in the lateral geniculate body

Changes in the parameters of responses of "low-frequency" and "high-frequency" neurons evoked in the lateral geniculate body by flashes or electrical stimulation of the optic nerve were investigated in immobilized and anesthetized rabbits after strychninization of the visual cortex. Under these conditions mainly an increase in the mean discharge frequency in the responses and a decrease in their latent periods were found in the "low-frequency" neurons, probable evidence of dominance of corticofugal facilitation. In most "high-frequency" neurons, on the other hand, the mean discharge frequency in the responses decreased and the latent periods were increased, evidence of dominance of corticofugal inhibition. It is suggested that reciprocal corticofugal influences exist on neurons connected with central and peripheral channels of the visual projection pathway.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow, Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 459–466, September–October, 1976.     

Retinopetal neurons and fibers in the lamprey

The structure of the retinopetal system was studied in the lamprey (Lampetra fluviatilis) using the horseradish peroxydase technique of axonal transport. Anterograde axonal transport within the retinofugal fibers had first been cut off by chemical destruction of the retina or severing the optic nerve, thereby enabling observation of retinopetal fibers unmasked by labeled visual afferents. Central neurons of the retinopetal systems could thus be distinguished bilaterally in the periventricular tegmental area of the midbrain and the mesencephalic reticular zone. Retinopetal fibers were traced in the structure of the axial optic tract.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Laboratory of Sensory Psychophysiology, Paris University VI, Paris, France. Translated from Neirofiziologiya, Vol. 17, No. 6, pp. 723–727, November–December, 1985.     

Effect of adequate stimulation on the discharge pattern of an isolated frog muscle spindle

Discharges from an isolated frog muscle spindle during mechanical stimulation of varied amplitude, velocity, and shape were investigated. The firing rate during a linear increase in strength of the stimulus is determined by its amplitude, whereas the change in firing rate is determined by the rate of increase of amplitude. With sinusoidal stimulation the firing rate apparently reproduces stimulus shape, i.e., the muscle spindle is sensitive not only to amplitude and velocity, but also to acceleration of the stimulus. Sensitivity to acceleration is most probably due to the change in threshold of appearance of action potentials observed during variation of the speed of stretching.P. K. Anokhin Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 426–433, July–August, 1976.     

Threshold and temporal characteristic of unit responses of the cat lateral geniculate body to electrical stimulation of the optic tract

Unit responses of the lateral geniculate body of the immobilized cat to electrical stimulation of the optic tract were studied. Responses of about 80 cells were compared and histograms of latencies and thresholds of their responses to electrical stimulation of their afferents were plotted. The distribution of the cells by latent periods was bimodal and by thresholds monomodal. Correlation was established between the various parameters of the cell reponses to electrical stimulation of afferents and to light. Correlation analysis showed that the cell population investigated is heterogeneous and consists of three groups.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 485–489, September–October, 1973.     

Changes in RNA content in neurons of the superior olivary complex during monaural and binaural stimulation

The character of binaural competitive connections at the level of the superior olive was investigated cytospectrophotometrically in cats. As a result of monaural stimulation for 2 h or binaural stimulation for 1.5 h by rhythmic noise signal the RNA content in the neurons of the ipsilateral and contralateral medial and lateral nuclei increased significantly. The volume of functioning neurons in the nuclei studied either increased or remained the same as in the control. The increase in the RNA content in neurons of both the ipsilateral and contralateral medial and lateral nuclei suggests a uniform distribution of binaurally converging connections on the neurons of these nuclei. The results also suggest that the accumulation of cytoplasmic RNA takes place in response not only to excitation, but also to inhibition.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 10, No. 1, pp. 67–74, January–February, 1978.