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.     

Organization of the afferent input in the rabbit superior colliculus

The organization of the afferent input into the superior colliculus was investigated in unanesthetized curarized rabbits. The afferent signal reaches the rabbit superior colliculus via at least two groups of fibers with mean conduction velocities of 3 and 6 m/sec. The components C₁ and C₂ of the evoked potential reflect postsynaptic unit activity arising after the arrival of impulses along these groups of fibers. This is confirmed by investigation of the shape of the evoked potential after stimulation of different points of the afferent pathway, data on conduction velocities, and comparison of single unit activity with the phases of evoked potential. The presence of components of this potential with short latent periods is evidence of predominance of the direct retinotectal input in the rabbit, a fact which may be connected with the lissencephalic type of brain development.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 281–289, May–June, 1977.     

Spatial configuration of rabbit superior collicular evoked response to punctiform afferent stimulation

Evoked potentials arising in the rabbit superior colliculus in response to punctiform stimulation of the receptive field were studied. This response has only negative polarity at the focus of maximal activity and does not exhibit reversal of the potential which is a characteristic feature of the response to diffuse stimulation. The evoked potential was recorded at depths of between 0.1 and 0.9–1.0 mm from the collicular surface, corresponding to the stratum griseum superficiale. The response disappeared when the stimulating spot was shifted through 4–6° away from the optical position. It is suggested that evoked potentials to punctiform stimulation can give more complete information on the location of different synapses.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 441–450, September–October, 1979.     

Functional organization of the tectothalamic section of the transcollicular visual afferent channel

On the basis of the results of electrical stimulation of the optic tract and upper layers of the superior colliculus in cats anesthetized with pentobarbital maps were compiled of the distribution of evoked potentials of the posterior thalamic nuclear complex, including the pulvinar and n. lateralis posterior, posterior, suprageniculatus, and lateralis dorsalis. Functional projections of the superior colliculus and optic tract to the posterior thalamus were shown to differ from each other. In response to stimulation of the superior colliculus the distribution of projections was more regular than to stimulation of the tract. Fibers running from the optic tract occupy a smaller territory than fibers from the superior colliculus. It is suggested that the transcollicular afferent channel of the visual system is not reduced in the course of evolution but, on the contrary, it acquires connections with the younger thalamic formations of the brain and assume more complex functions.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 10, No. 4, pp. 355–359, July–August, 1978.     

Hypothalamic influences on unit activity in the cat superior colliculus

Experiments on immobilized unanesthetized cats showed that hypothalamic stimulation effectively modified spontaneous unit activity and activity evoked by photic stimulation in the superior colliculus. Long-latency responses, often with a tonic type of formation, were predominant. Meanwhile, definite differences were found in the character of influences from different regions of the hypothalamus. Stimulation of the anterior hypothalamic region and lateral hypothalamus led more frequently to inhibition of spontaneous activity, often expressed as the development of initial inhibition, especially during stimulation of the lateral hypothalamus. Definite modulation of spontaneous activity of cyclic type also developed. Influences from these structures on activity evoked by photic stimulation were chiefly facilitatory and modulating in character. Stimulation of the ventromedial nucleus could produce inhibitory and facilitatory effects equally on activity of tectal neurons, with a tendency for the frequency of manifestation of facilitation to increase when a series of stimuli was used. The mechanisms of triggering and realization of hypothalamic influences on activity in the superior colliculus are discussed.Ivano-Frankovsk State Medical Institute, Ministry of Health of the Ukrainian SSR. Translated from Neirofiziologiya, Vol. 11, No. 6, pp. 560–568, November–December, 1979.     

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.     

Control of conduction of afferent impulses across the lateral geniculate body by the side of the superior colliculus in alert rabbits

On alert rabbits it was shown that the stimulation of the superior colliculus inhibit visual evoked potential both of the ipsi- and contralateral geniculate body. Besides, the suppression of amplitude of the contralateral geniculate body's evoked potential was more significant than amplitude of the ipsilateral geniculate body's evoked potential. On the basis of the obtained results the authors suppose that superior colliculus is involved in organization of the effect of saccadic suppression of lateral geniculate body's visual responses.     

Features of evoked potentials in the cerebellar cortex of rabbits

We investigated evoked responses of the cerebellar cortex of rabbits under Nembutal or chloralose anesthesia to stimulation of the sciatic, brachial, and vagus nerves. The parameters of evoked potentials (E Ps), together with features of their distribution throughout the cerebellar cortex, enabled us to divide them provisionally into three types. Evoked potentials of the first type have a latent period of 5–10 msec and a two-phase or more complex shape. Evoked potentials of the second type have a latent period of 10–23 msec and include from one to four components. Evoked potentials of the third type are discharges with long latent periods (20–50 msec) and consist of a series of slow sinusoidal oscillations. Appearance of an initial electronegative component is characteristic of EPs of the cerebellar cortex of rabbits, especially those of the second and third types. Evoked potentials of the first type are local.N. I. Pirogov Vinnitsa Medical Institute. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 73–80, July–August, 1969.     

Depression of evoked potentials in rat thalamic ventro-basal complex and somatosensory cortex after reticular stimulation

Experiments on unanesthetized rats immobilized with D-tubocurarine showed that electrical stimulation (100/sec) of the central gray matter and the mesencephalic and medullary reticular formation considerably depressed potentials in the somatic thalamic relay nucleus and somatosensory cortex evoked by stimulation of the forelimb or medial lemniscus. The mean threshold values of the current used for electrical stimulation of these structures did not differ significantly and were 70 (20–100), 100 (20–120), and 120 (50–200) µA, respectively. On comparison of the amplitude-temporal characteristics of inhibition of evoked potentials during electrical stimulation of the above-mentioned structures by a current of twice the threshold strength, no significant differences were found. Immediately after the end of electrical stimulation the amplitude of the cortical evolved potential and the post-synaptic components of the thalamic evoked potential was 50–60% (P<0.01) below the control values. The duration of this depression varied from 0.5 to 1 sec. An increase in the intensity of electrical stimulation of brain-stem structures to between three and five times the threshold led to depression of the presynaptic component of the thalamic evoked potential also. Depression of the evoked potential as described above was found with various ratios between the intensities of conditioning and testing stimuli.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 8, No. 5, pp. 467–475, September–October, 1976.     

Cortical distribution of photic evoked potentials

Short-latency evoked potentials (EPs) of the primary response (PR) type, recorded to flashes over wide areas outside the visual cortex, reflect the true arrival of visual impulses in these areas and are not the result of the passive spread of the EPs over the brain tissue. The EPs do not disappear after extirpation of the visual cortex in "nonvisual" areas of the neocortex. They continue to arise also after division of the internal capsule sparing its posterior third. EPs are no longer recorded after division of the posterior third of the internal capsule. It is concluded from these results that the spread of impulses evoked by photic stimulation, not only into the visual areas, but also into other areas of the posterolateral thalamic nuclei.S. M. Kirov Medical Institute, Gor'kii. Translated from Neirofiziologiya, Vol. 2, No. 5, pp. 482–487, September–October, 1970.     

Retrieval of delayed evoked potentials after amygdaloid stimulation

The effect of amygdaloid stimulation on retrieval of delayed evoked potentials recorded in the cortex, mesencephalic reticular formation, lateral geniculate body, and hippocampus was investigated in unanesthetized curarized cats. Delayed evoked potentials were produced to 10–400 combinations of flashes and hypothalamic stimulation and consisted of potentials arising in response to a conditioned stimulus after a delay equal to the interval between it and the unconditioned stimulus. Amygdaloid stimulation facilitated the retrieval of these potentials if they had first been extinguished or had not appeared during initial testing.Institute of Physiology, Academy of Medical Sciences of the USSR, Siberian Branch, Novosibirsk. Translated from Neirofiziologiya, Vol. 8, No. 3, pp. 300–304, May–June, 1976.     

Laminar distribution of current sources in the rabbit superior colliculus during optic nerve stimulation

The electric field of evoked potentials developing in the rabbit superior colliculus in response to single electrical stimulation of the optic nerve was investigated. Regions of localization of sources and sinks of synaptic current creating the evoked potential were discovered by the current source density analysis method. Sinks with the shortest latency appeared in the depth of str. griseum superficiale, after which activity created by two dipoles appeared: The sink of one dipole was located in the upper part of str. griseum superficiale, the sink of the other in the lower part. The sinks thus found corresponded in their temporal characteristics and location to the principal components of the combined evoked potential. On the basis of these data the order of activation of the various systems of fibers and synapses responsible for evoked potential formation can be traced.     

Transthalamic conduction of visual impulses to the cortex and subcortical forebrain structures in turtles

The thalamic relays for the conduction of impulses arising during photic stimulation of the eyes and electrical stimulation of the tectum in the general cortex, hyperstriatum (the dorsal ventricular ridge), and the striatum proper were studied in the turtleEmys orbicularis. Acute experiments on immobilized animals showed that anodal polarization temporarily and destruction of n. rotundus irreversibly suppress the main negative wave of the responses to tectal stimulation and to flashes in the hyperstriatum, whereas the corresponding responses in the general cortex still persist. Polarization and destruction of the lateral thalamic region, including the lateral geniculate body, have the opposite effect: responses in the hyperstriatum to photic and tectal stimulation are virtually unchanged whereas those in the general cortex disappear, except their late components. Preceding single stimulation of the tectum or n. rotundus depresses responses in the hyperstriatum evoked by flashes. However, during stimulation of the lateral thalamic region, combined potentials and single unit responses appear in the hyperstriatum and interact with responses evoked by tectal stimulation. It is concluded that the main pathways in turtles which supply visual information to the general cortex and hyperstriatum differ: the former relay in the lateral thalamic region, the latter in n. rotundus, although some overlapping of their projections in the hyperstriatum and striatum is possible.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 486–494, September–October, 1977.     

Effects of stimulating the superior colliculus on motoneurons of the neck muscle in the cat

Postsynaptic potentials produced by stimulating three sites of the midbrain superior colliculus were examined in motoneurons innervating the sternocleidomastoid, the trapezius, and the platysma cervical muscles in anesthetized cats. Stimulating the ipsilateral colliculus produced EPSP in the motoneurons as well as action potentials with a latency of 1.5–3.5 msec, averaging 2.6 ± 0.1 msec. Stimulation of the contralateral colliculus evoked EPSP with a latency of 1.5–3.2 msec and averaging 2.1 ± 0.1 msec together with IPSP with latency ranging from 2.6 to 5.0 msec. It is postulated that these postsynaptic responses are both monosynpatic and bisynaptic in nature. This type of synaptic action is assumed to be one of the mechanisms responsible for coordinated head movements produced by tectofugal impulses.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 2, pp. 197–202, March–April, 1986.     

The synaptic distribution of the retinal input in the superficial layers of the guinea-pig superior colliculus

An evoked potential consisting of four postsynaptic components was recorded in the guinea-pig superior colliculus following electrical stimulation of the contralateral optic nerve. This potential was generated in response to the activation of four populations of optic nerve fibres with different conduction velocities. Current source-density analysis revealed that the two slower conducting fibre populations synapse in the upper third of the stratum griseum superficiale on dendrites whose cell bodies appear to be found in the lower part of this layer and in the stratum opticum. The two faster conducting populations synapse deeper, near the border of the stratum griseum superficiale and stratum opticum, on neurons with cell bodies that may lie towards the upper part of the stratum griseum superficiale. The locations of these postsynaptic sites correspond to the layers in which the optic nerve terminates as revealed by neuroanatomical tracing techniques. Furthermore, neurons of the shape and orientation predicted by the current source-density analysis were found in the superficial layers by using the Golgi-Cox technique.     

Effect of stimulation of hypothalamic preoptic region on activity in single fibers of the rabbit optic tract

The statistical characteristics of spontaneous activity and activity evoked by flashes in single fibers of the optic tract were compared before and after stimulation of the preoptic region of the hypothalamus in rabbits immobilized with listhenon. Analysis of the results shows that the effect of high-frequency stimulation of the hypothalamic preoptic region correlates with the character of responses to flashes recorded from fibers of the optic tract. More often stimulation of the hypothalamic preoptic region led to an increase in the spontaneous discharge frequency in the optic tract fiber and to facilitation of the response to flashes. Responses of phasic type to flashes with a short latent period (42 msec), consisting of a long series of spikes, and responses of tonic type with a long latent period (155 msec) were facilitated to a greater degree. Responses of phasic type to flashes with a short latent period (35 msec), consisting of a short series of spikes, usually were not facilitated after stimulation of the hypothalamic preoptic region. The results suggest the presence of influences of complex character on the rabbit retina from the preoptic region of the hypothalamus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neiorofiziologiya, Vol. 10, No. 5, pp. 494–503, September–October, 1978.     

Localization and characteristics of parasympathetic preganglionic neurons in the sacral spinal cord

Antidromic responses of parasympathetic preganglionic neurons (PPN) in the sacral spinal cord evoked by stimulation of the pelvic nerve were studied in acute experiments on anaesthetized and immobilized cats by means of extracellular recording technique. The conduction velocities for preganglionic axons were calculated from the latency of these responses. It was shown that the upper limits of the conduction velocities for sacral parasympathetic axons extended the range (limit 12–15 m/sec) previously described: The velocities varied from 0.9 to 30.5 (mean 11.3±0.47) m/sec. According to the axonal conduction velocities the PPN were divided into four groups: the first group with conduction velocities from 0.9 to 3.0 m/sec; the second — 4.0–12; the third — 13–21; and the fourth group — 21–30 msec. PPN of the second group quantitatively prevailed — 57.6%, those of the third group represented 29.9%, and those of the first and fourth groups 6.8 and 6.2% of the total amount of PPN, respectively. Relative topic specialization of the second and third PPN groups was revealed. The density of PPN distribution in the intermediolateral region was higher in the second group than in the third one, while in ventral parts of the ventral horn concentration of the third PPN group was higher than that of other groups. The functional significance of PPN from the third group with fast-conducting axons (the conduction velocities correspond to those of group B fibers) is discussed.Translated from Neirofiziologiya, Vol. 25, No. 1, pp. 39–45, January–February, 1993.     

The Impact of Spatial Incongruence on an Auditory-Visual Illusion

Background

The sound-induced flash illusion is an auditory-visual illusion – when a single flash is presented along with two or more beeps, observers report seeing two or more flashes. Previous research has shown that the illusion gradually disappears as the temporal delay between auditory and visual stimuli increases, suggesting that the illusion is consistent with existing temporal rules of neural activation in the superior colliculus to multisensory stimuli. However little is known about the effect of spatial incongruence, and whether the illusion follows the corresponding spatial rule. If the illusion occurs less strongly when auditory and visual stimuli are separated, then integrative processes supporting the illusion must be strongly dependant on spatial congruence. In this case, the illusion would be consistent with both the spatial and temporal rules describing response properties of multisensory neurons in the superior colliculus.

Methodology/Principal Findings

The main aim of this study was to investigate the importance of spatial congruence in the flash-beep illusion. Selected combinations of one to four short flashes and zero to four short 3.5 KHz tones were presented. Observers were asked to count the number of flashes they saw. After replication of the basic illusion using centrally-presented stimuli, the auditory and visual components of the illusion stimuli were presented either both 10 degrees to the left or right of fixation (spatially congruent) or on opposite (spatially incongruent) sides, for a total separation of 20 degrees.

Conclusions/Significance

The sound-induced flash fission illusion was successfully replicated. However, when the sources of the auditory and visual stimuli were spatially separated, perception of the illusion was unaffected, suggesting that the “spatial rule” does not extend to describing behavioural responses in this illusion. We also find no evidence for an associated “fusion” illusion reportedly occurring when multiple flashes are accompanied by a single beep.     

Frühe Antwortkomponenten im photisch evozierten Potential beim Kaninchen und beim Menschen

Zusammenfassung Nach schwachen Lichtblitzen beginnt das ERG des Kaninchens mit einer Anzahl rascher Komponenten (Frequenz um 700 Hz). Unter photopischen Bedingungen (Rotblitze) können 11 solche Komponenten auftreten, anschließend folgen langsamere Schwankungen. Reizung mit einer hochfrequenten Blitzperiode (300–500 Hz) synchronisiert den Antwortrhythmus nach der 4.–7. Komponente, gleichzeitig wächst die Zahl der raschen Komponenten. In der photisch evozierten Rindenantwort des Menschen erscheinen Oszillationen um 180 Hz. Die Rindenantwort des Menschen kann schon nach 15,4 msec beginnen; die frühen Antwortkomponenten erscheinen oft erst nach längerer Sitzungsdauer.Die Befunde von Docampo et al. (1967), nach denen unter Nembutal die photisch evozierte Rindenantwort in der vorderen Sehrinde des Kaninchens zuin der hinteren abnimmt, konnten nicht bestätigt werden. Bei Nembutal-Dyspnoe trat eine Verkleinerung der Antwortkomponente II auf. Starke Elektronenblitze werden vom Auge weniger gut ausgenützt als schwächere.

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Early components in photic evoced potentials in rabbits and in man

Summary In the beginning of the ERG in rabbits dim light flashes evoke several fast components with a frequency of about 700 c. Photopic conditions, such as red light flashes elicit 11 fast components followed by slower deflexions. Stimulation with a high frequent period (300–500 c) of flashes sychronises and multiplies the oscillations of potential after the 4.–7. component. Periodic oscillations of about 180 c appear in the photically evoked response of human striate Area. Latencies as small as 15,4 msec were showed, especially in long lasting experiments. Docampo et al. (1967) have reported, that the photically evoked response increases in the anterior and decreases in the posterior striate Area of the rabbit, if the animal is treated by Nembutal. This is not confirmed by our experiments, which yielded only smaller amplitudes of component II in the state of dyspnoe caused by Nembutal. The eye utilises dim electronic flashes better than stronger ones.

     

Participation of nonsegmentary neurons of the spinal cord in execution of presynaptic control

Experiments were carried out on cats six days after complete transection of the spinal cord. Cord dorsum potentials (CDP) were recorded in the vicinity of the third lumbar segment during stimulation of the isolated dorsolateral funiculus (DLF). The CDP consist of a rapid monophasic potential (which apparently reflects antidromic excitation of the cells of Clarke's column) and two subsequent slow negative waves, which are replaced by a long positive oscillation. In form, time characteristics, and behavior during thythmic stimulation, this potential differs considerably from the CDP recorded during stimulation of the afferent nerves. The presence of a positive phase of the CDP indicates that stimulation of the DLF evokes primary afferent depolarization (PAD). Stimulation of the DLF causes inhibition of the CDP evoked by stimulation of the afferent nerve. The time course of this inhibition corresponds to the time course of presynaptic inhibition. It is demonstrated that stimulation of the afferent nerve (n. femoralis) inhibits slow components of the CDP evoked by stimulation of the DLF. This inhibition reaches a maximum at the 16th millisecond; its duration exceeds 300 msec. Stronger and more prolonged inhibition of the same components is observed when both the conditioning and the testing stimuli are administered to the DLF. Since primary afferents do not take part in CDP emergence during stimulation of the DLF, it may be hypothesized that the observed inhibition develops as a result of depolarization of interneuron axon terminals.Dnepropetrovsk State University. Translated from Neirofiziologiya, Vol. 2, No. 5, pp. 520–527, September–October, 1970.