Sustained potential shifts in the toad tectum reflect prey-catching and avoidance behavior.

Sustained potential shifts (SPS) were recorded for 10 s from the surface of the optic tectum of toads presented with live prey and moving artificial prey stimuli. On the anterior tectal surface, a negative SPS was followed by a positive wave; the converse was true for the posterior tectum. Some animals were immobilized, and they exhibited a monophasic negative SPS in the anterior tectum and a positive wave in more posterior regions. The number of orienting responses made by toads to moving "wormlike" stimuli was reflected in the amplitude of the SPS, as was avoidance to stimuli in an "antiworm" configuration. Behavioral activity was most closely related to the negativity of the SPS recording. The SPS of toads responding to live prey showed no direct time relationship between the SPS and behavior, suggesting that the SPS reflects sensory or decision-making activity rather than the consequent behavior.

Dendritic and sustained shifts in potential to electrical stimulation of the anuran tectal surface.

1. Recordings of dendritic potentials and sustained potential shifts (SPS) were made from the brain of immobilised frogs during surface tectal electrical stimulation. 2. Single pulses evoked dendritic responses; trains caused decay of dendritic responses on the background of the evoked SPS. 3. The tectal surface SPS declined with distance from the stimulating electrode. 4. The negative surface SPS declined with tectal depth to ca 300 microns, then reversed polarity and increased in amplitude with depth up to 700 microns.

Posttetanic potentiation of primary response and late negative wave in the somatosensory region of the cortex of the cat.

The experiments were carried out on cats under nembutal anesthesia. Stimulation of the ventroposterolateral nucleus of the thalamus or the white matter by a single stimulus elicited a primary response in the middle layers of the somatosensory cortex, and after it, a late negative wave, the duration of which reaches 40-70 msec. This potential does not have dipole reflection on the surface of the cortex and is apparently generated primarily by stellate cells. As a result of the tetanization of the ventroposterolateral nucleus or the white matter, a sharp increase in the amplitude of the late negative wave is observed, i.e., its posttetanic potentiation, while the primary response changes to a significantly lesser degree. Posttetanic potentiation is observed for 2-2.5 h. Posttetanic potentiation of the late negative wave is probably governed by processes occurring at the level of the middle layers of the cerebral cortex.

[Negative change in the potential of the cat cerebral cortex after transcallosal stimulation]. / Otritsatel'nyi sdvig potentsiala kory mozga koshki pri transkallozal'nom razdrazhenii.

The slow negativity (SN) evoked with rhythmic transcallosal stimulation in anesthetized cats is generated in the upper layers of the cortex. The amplitude and duration of SN increased after the application of tetraethylammonium solution to the surface of the cortex. The SN seems to reflect mainly the glial depolarization.

[Changes in the concentration of extracellular potassium in the cerebral cortex with different parameters of electrical stimulation]. / Izmeneniia kontsentratsii vnekletochnogo kaliia v kore mozga pri raznykh parametrakh ee élektricheskogo razdrazheniia.

In anesthetized cats, a recording macroelectrode, a K+-sensitive microelectrode and a stimulating electrode were placed on the surface of the suprasylvian gyrus. As the duration or intensity of stimulus increased, the amplitude of K+-potential reflecting the changes in the extracellular concentration of K+ ions (delta [K+]o) was augmented, while the half time of decay decreased. delta [K+]o also increased when the number of stimuli increased. Repetitive tetanic stimulation resulted in impairment of the effect also in the case when [K+]o following the preceding stimulus, reached the initial level. K-potential started to decay in the course of prolonged tetanic stimulation; impairment of the neuronal activity is supposed to underlie this event.

[Slow electrical potentials arising after the initial response in the somatosensory cortex of the brain of the cat upon stimulation of the ventroposterolateral nucleus of the thalamus]. / Medlennye élektricheskie potentsialy, voznikaiushchie posle pervichnogo otveta v somatosensornoi oblasti kory mozga koshki pri razdrazhenii ventroposterolateral'nogo iadra talamusa.

Experiments were carried out on cats under pentobarbital anaesthesia. A single electrical stimulus applied to the VPL nucleus evoked in g. sigmoideus posterior a primary response, followed by delayed negative wave and slow negativity. Generation of these potentials was accompanied by three spike-like deflections in the subcortical white matter. The delayed negative wave was generated in the middle layers of the cortex and was not reflected on its surface. The slow negativity correlated with a transient increase in extracellular potassium concentration. It is suggested that the delayed negative wave reflects the excitation of stellate cells, slow negativity--mainly glial depolarization. The generation of three mentioned responses is connected with the arrival of excitation to the cortex via three systems of afferent fibres projecting from the VPL nucleus to the somatosensory cortex.

[Non-synaptic inhibition in the cortex of the cat]. / O nesinapticheskom tormozhenii v kore mozga koshki.

Experiments were carried out on cats under pentobarbital anaesthesia. Two stimulating electrodes (S1 and S2), a recording macroelectrode and K+-selective microelectrode were placed on g. suprasylvius. A strong stimulus applied through S1 elicited slow negativity (SN) and increase in [K+]o. At that time the dendritic potential (DP) evoked by stimulation through S2 was depressed. The depression of DP correlated with the voltage of SN and with the level of [K+]o. It is suggested that DP depression is caused by presynaptic action of K+ ions.

[Changes in the concentration of extracellular potassium and the slow negative potential in the somatosensory area of the cortex in response to stimulation of the ventroposterolateral nucleus of the thalamus in the cat]. / Izmeneniia kontsentratsii vnekletochnogo kaliia i medlennyi otritsatel'nyi potentsial v somatosensornoi oblasti kory pri razdrazhenii ventroposterolateral'nogo iadra talamusa koshki.

A single electrical stimulus applied to the VPL nucleus with intensity, strong enough to elicit in gyrus sigmoideus posterior slow negativity following the primary response, caused a local increase in [K+]0 reaching 0.2 mM. On the basis of this finding it is supposed that the slow negativity reflects mainly depolarization.

[Changes in the concentration of intracellular potassium and the phenomenon of dendritic potential depression against a slow negative potential background in the cat cerebral cortex]. / Izmeneniia kontsentratsii vnekletochnogo kaliia i fenomen ugneteniia dendritnogo potentsialav na fone medlennogo otritsatel'nogo potentsiala kore mozga koshki.

Two stimulating electrodes (S1 and S2), a recording macroelectrode and a K+-selective microelectrode were placed on g. suprasylvius of cat. A stimulus applied through S1 elicited slow negativity and an increase in [K+]0. At this time the dendritic potential evoked by stimulation through S was depressed. The depression of the dendritic potential was found to correlate with [K+]0.

[Changes in the extracellular potassium concentration and the slow negative potential in the cerebral cortex]. / Izmeneniia kontsentratsii vnekletochnogo kaliia i medlennyi otritsatel'nyi potentsial v kore mozga.

Changes of potassium concentration in the extracellular space ([K+]0) of the g. suprasylvius of cat cerebral cortex were recorded by means of K+ selective microelectrodes; the electrical field potential was recorded simultaneously. Under deep anesthesia a single electrical stimulus, applied to the cortical surface, at intensity enough to elicit the slow negativity, caused a local increase of [K+]0 reaching 0.1-1.5 mM. The time course of the K+ signal coincide with the course of the slow negativity. It is supposed that the slow negativity reflects glial depolarizaion arising under the action of K+ ions.