Generalization of defensive conditioned reflexes elaborated to electrical stimulation of the lateral hypothalamus (LH) was studied in four dogs with electrodes implanted in various structures of the limbic system. Electrocutaneous stimulation was switched off when the dog lifted the foreleg to a definite level. Generalization of the conditioned reflex was manifested in different degrees when testing different formations of the limbic system, or testing one and the same structure, but at different stages of conditioning. Two types of generalization were found: the first one--a well pronounced motor reaction, by its latency, level and duration of lifting the foreleg similar to movements appearing in response to the conditioned stimulus; and the second one--low amplitude or short-term movements differing from conditioned ones. The first type of generalization was observed in response to stimulation of LH, contralateral to the point of signal stimulation, of the ventromedial hypothalamic nucleus, the mammillary bodies and the basal, lateral and to a lesser degree, the central nucleus of the amygdaloid complex; the second type--in response to stimulation of the ventral hippocampus, the medial and lateral septum nuclei.

Amygdala↗

PubMedDate not supplied

[Instrumental defensive conditioned reflexes to electric stimulation of the hypothalamus in dogs].

An instrumental defensive conditioned reflex to electrical stimulation of the lateral hypothalamus (LHS) was elaborated in seven dogs with electrodes implanted in different structures of the limbic system. Electrocutaneous stimulation was disrupted by a lift of the foreleg to a certain level. The conditioned reflex developed slowly: it appeared at the 15th to 35 th pairing, became stable by the 120--150th pairing of stimuli and reached a 60--90% level. Extinction of the conditioned reflex took 70--80 presentations of the conditioned stimulus without reinforcement. As LHS turned into a signal of electrocutaneous stimulation, the typical reactions to it weakened; in particular, searching movements and sniffing virtually disappeared, while licking movements appeared much more seldom both during the action of the conditioned stimulus and in the intervals between stimuli pairings.

Amygdala↗

PubMedDate not supplied

[The autonomic component of food and defensive conditioned reflexes acquired to bursts of light and electrostimulation of the limbic structures and the basal ganglia].

Alimentary and defensive instrumental conditioned responses (CRs) to light flashes, electrical stimulation of the dorsal hippocampus and the nucleus caudatus were elaborated in seven dogs. These CRs were tested by electrostimulation of the limbic structures and the basal ganglia. Motor and vegetative components of CRs were compared. If there occurred an instrumental movement during the conditioned stimulus the heart rate increased with a high probability. If there were no movement the heart rate increase approached the level of significance only in five dogs of seven. The heart rate always increased in the positive generalization tests while in the negative ones the heart rate either decreased or increased to a lesser degree.

Animals↗

PubMedDate not supplied

[The similarity and difference between dogs assessed by the indices of the summary electrical activity of the frontal cortex, hippocampus, amygdala and hypothalamus].

Eight dogs were bilaterally implanted with stainless steel electrodes in dorsal and ventral hippocampi (DHp, VHp), basolateral amygdala (BLA), lateral hypothalamus (LH) and with silver spherical electrodes in the frontal cortex (FC). The EEG of these structures was recorded in the state of wakefulness without any stimulation. Rhythmical activity in the theta (4.4 +/- 0.05 Hz) and alpha (10.7 +/- 0.2 Hz) ranges was revealed in all the dogs. Rhythm of the beta-2 range (22.4 +/- 0.1 Hz) was recorded in four, and that of the beta-3 (37.8 +/- 0.5 Hz) only in two of the animals. The mean frequency of the theta-rhythm recorded in the LH was higher (p < 0.001) than that in the VHp and AMB. The spectral density in the theta range was higher in the VHp than that in the other structures (p < 0.01). The same values for the DHp and AMB were higher that for the LH (p < 0.001) and FC (p < 0.01). The spectral densities in the right DHp and VHp were higher than in the symmetrical left derivations (p < 0.001). The dogs were different in the expression of specific rhythms, their frequency and power. These characteristics depended on the degree of emotional excitation and motor activity of the dogs during recording of the electrical activity.

Amygdala↗

PubMedDate not supplied

[The effect of anxiolytics and an anxiogen on the electrical activity of the frontal cortex and limbic structures of dogs with different nervous system properties].

The influence of benzodiazepine anxiolytics (diazepam, medazepam, nozepam) and anxiogen corasole on the electrical activity of the dorsal hippocampus, frontal cortex, basolateral amygdala, and lateral hypothalamus was studied in 8 dogs with implanted electrodes. The anxiolytics decreased anxiety and reduced the theta-rhythm frequency in all the structures under study. The effect was most pronounced in the dorsal hippocampus. The excitable dogs with initially more frequent theta rhythm turned to be less sensitive to diazepam than more calm animals with prevailing inhibition. The higher dose of diazepam was necessary for excitable dogs to obtain the same electrophysiological effect. At the end of the drug action, the theta-rhythm power significantly increased in the dorsal hippocampus in all the animals, and in the excitable dogs it increased also in the frontal cortex. Moreover, diazepam produced as decrease in the beta 2-frequency and increase in the frequency of the alpha-like rhythm. The anxiogen intake resulted in an increase in dogs' alertness and motor activity, accompanied by an increase in the theta-rhythm frequency. Anxiogen increased the frequency asymmetry of theta between hemispheres in the hippocampus and amygdala.

Animals↗