Wanda Wyrwicka

Instrumental Conditioning of Sensorimotor Cortex EEG Spindles in the Waking Cat

Abstract The spontaneous occurrence of a 12–20 cps slow-wave spindle recorded from sensorimotor cortex in waking food-deprived cats was systematically reinforced by presentation of milk. This specific EEG pattern was detected by a filter-relay system, the discharge of which was capable of activating the feeding apparatus within an experimental behavior chamber. After several sessions, with 50 reinforcements per session, this sensorimotor rhythm appeared more frequently and demonstrated a regular temporal pattern of occurrence. The consistent behavioral correlate of this EEG response was the assumption of stereotyped postures, characterized by a complete cessation of spontaneous activity. Withholding milk reinforcement resulted in a considerable enhancement of the sensorimotor rhythm during the initial period of extinction. Such changes were not observed, however, when other patterns of sensorimotor cortex electrical activity were reinforced in a similar manner. We conclude that, in the present experiments, it was possible to establish a conditioned sensorimotor cortex slow-wave response of the instrumental type, and that this sensorimotor rhythm has functional significance as a conditioned “central state” related to the inhibition of phasic motor behavior.

Post-reinforcement EEG synchronization during alimentary behavior

Abstract 1. 1. Cats were trained to manipulate a lever which delivered small amounts of liquid food (milk-broth) from a dispenser. Discrete periods of EEG synchronization were observed coincident to the development of this simple instrumental response. 2. 2. Slow wave synchronous activity in the EEG replaced low voltage fast activity when the animals received positive reinforcement. These “spindles” did not appear if the animals were not reinforced. They could be abolished by thalamic electrical stimulation at arousal parameters or by novel auditory stimuli, even though these internal and external stimuli were not intense enough to alter the behaving pattern of the cats in the instrumental situation. 3. 3. Water substituted for the milk-broth reward in a food deprived animal resulted in a disappearance of the post-reinforcement cortical synchronization. 4. 4. The EEG synchronization previously described during prolonged alimentary behavior was also observed in our animals under these circumstances. 5. 5. The presentation of a sensory stimulus in association with the delivery of larger amounts of food resulted in the classical conditioning of this synchronization. Extinction of the conditioned synchronization was also achieved. The prolonged presentation of a non-reinforced CS resulted in the reappearance of a synchronization, which, in this case, was associated with the extinction of an alimentary response.

Acceptance of high concentration saccharin solutions by cats after hypothalamic lesions.

Abstract Twenty cats with monopolar electrodes implanted bilaterally in the posterior, lateral or rostral hypothamus were deprived of water and trained to press a lever to obtain distilled water or to press another lever to obtain saccharin solution. It was found that the cats initially preferred saccharin solution over distilled water, but when concentration of saccharin in solution was higher than 2.0–3.0% most animals refused to accept it and drank only distilled water. Bilateral hypothalamic lesions made through the implanted electrodes resulted in acceptance of saccharin solutions of high concentrations (5–7%), although a considerable decrease in the intake of both distilled water and saccharin solution was observed during several weeks after lesions. The strongest effect was found in those cases in which lesions involved medial forebrain bundle, zona incerta, and fields of Forel.

Effect of electrical stimulation of the dorsal nucleus of the vagus nerve on gastric acid secretion in cats.

Abstract Electrical stimulation of 3 to 9 V, 100 impules/s 1-ms duration/impulse, applied to the right or left dorsal motor nucleus of the vagus nerve (DNV) produced a significant increase in volume, acidity, and gastric acid output in 14 cats under sodium pentobarbital anesthesia. The increase in acid output occurred during the first 15 min of stimulation or immediately after the stimulation and in some cats lasted for the next 30 min to more than 2 h. In no case did the stimulation within the DNV evoke a decrease in gastric acid secretion. Similar electrical stimulation in sites outside the DNV had no effect on gastric acid secretion. Motor effects such as opening of the mouth, movements of the tongue and whiskers, and salivation were observed to occur randomly during stimulation at sites both inside and outside the DNV zone and were not correlated with changes in gastric acid secretion. After recovery from the acute experiment, two cats were tested under chronic conditions. Electrical stimulation with low voltage applied to the previously effective electrode tips repeatedly produced an increase in the volume of secretion in one cat and an increase in both volume and acidity of secretion in the other cat. This study provided further evidence that the DNV is a secretomotor center.

Forebrain inhibitory mechanisms: conditioning of basal forebrain induced EEG synchronization and sleep.

Abstract There is evidence suggesting that EEG synchronization and sleep are capable of becoming associated with specific sensory stimuli through the process of conditioning. In some preliminary experiments it was found that the EEG and behavioral patterns induced by basal forebrain stimulation could be evoked by a tone which had been paired in time with electrical stimulation of this area in the cat. The present experiments are concerned with a closer examination of this conditioning. Adult cats were surgically prepared for chronic study with stimulating electrodes lowered bilaterally into the basal forebrain synchronizing area and the intralaminar thalamic nuclei with recording electrodes placed diffusely in the calvarium over the cerebral cortex. After recovery, these animals were placed in an observation chamber and presented with a fixed interval conditioning sequence of tone followed by basal forebrain stimulation. A conditioned EEG synchronization accompanied by behavioral manifestations of sleep developed rapidly to the tone when either low- (5 cycle/sec) or high- (150 cycle/sec) frequency stimulation in the basal forebrain was used as the unconditioned stimulus. Generalization of the conditioned response was observed when tone frequencies were changed, and discrimination developed in relation to a different tone paired with high-frequency (alerting) stimulation of intralaminar thalamic nuclei. A relationship between the frequency of basal forebrain stimulation and that of the conditioned EEG synchronization was also observed. These findings support the conclusion that important functional connections exist between the basal forebrain synchronizing areas and the cerebral cortex.

Sensory regulation of food intake

Abstract Some observations suggest the existence of projections from the receptors of the oral cavity and the stomach to the brain areas known to be related to feeding. Sensations produced by eating food may originate in these structures. A suggestion is made that the shortterm regulation of food intake is directed by oro-gastric sensations which may vary depending on the conditions of the internal environment.

The sensory nature of reward in instrumental behavior

Improvement in the sensory state, or “better-being,” achieved either through obtaining desirable sensations or through escaping undesirable sensations, is considered the essential value which maintains the instrumental behavior. This value may vary depending on such factors as the intensity of the stimulus producing sensations, the effects of its previous occurrence, and the changes in the internal and external environment. Methods of evaluation of sensory “better-being” by means of measuring instrumental, autonomic and EEG responses are discussed.

Imitation of mother’s inappropriate food preference in weanling kittens

Experiments were performed on four mother cats and their 22 kittens from 7 litters. Each mother was trained to eat banana or mashed potato in the presence of meat pellets in order to get a hypothalamic stimulation reward. Eighteen of twenty-two weanling kittens which accompanied the mother during the session imitated the mother in eating banana or potato and ignored meat pellets. The imitation of the mother started not earlier than at 35 days of age and in most kittens (10 of 18) began between 49 and 56 days of age. The kittens which ate banana or potato with the mother also ate that food when tested alone after weaning at 9 to 27 weeks of age, either during 10 min sessions in the experimental compartment or during 24 hr tests in the home compartment. When banana was offered to 9 control 13–23 week old kittens (of three other mothers) who never before had eaten that food or had seen their mother eat it, 8 of them did not consume banana during three 24 hr tests. Some consumption, however, occurred in the ninth kitten during the third of these tests. It has been concluded that weanling kittens in the period of transition from maternal to independent feeding tend to imitate the mother in food preferences, even if the food chosen by the mother is unusual for their species. The food preferences acquired through the imitation of the mother may influence the food preferences at the later stages of life.

Conditioning of Induced Electroencephalographic Sleep Patterns in the Cat

Stimulation of the basal forebrain synchronizing area of the cat induces the behavioral and electroencephalographic manifestations of sleep. By pairing such stimulation with a neutral auditory stimulus we were able to evoke electroencephalographic synchronization and sleep preparatory behavior to the presentation of a tone, and to temporal factors associated with the conditioning procedure.

Effects of electrical stimulation within the hypothalamus on gastric acid secretion and food intake in cats.

Abstract The effect of electrical stimulation within the hypothalamus on gastric acid secretion was studied in 43 cats under both acute and chronic conditions. In a study on 36 cats anesthetized with sodium pentobarbital, gastric acid secretion induced by the iv infusion of pentagastrin was increased during and/or 15 to 75 min after stimulation in the anterior hypothalamus in 13 of 31 cats tested, and in the midlateral hypothalamus in 2 of 11 cats tested; no changes in acid secretion were found during or after stimulation in the medial hypothalamus in 11 cats tested. Seven cats in which stimulation in the anterior hypothalamus increased acid secretion were allowed to recover and were later tested under chronic conditions. In three of these cats stimulation of the previously effective sites repeatedly produced an increase in basal acid secretion. Similar stimulation in four other cats was effective in some sessions and ineffective in others. During a behavioral test all these cats showed the following effects of stimulation: restlessness, meowing, and and attempting to escape. None ate during stimulation, although occasional licking was observed. Another experiment was carried out on seven cats with electrodes implanted in the midlateral hypothalamus (six cats) or in the anterior hypothalamus (one cat). In these cats electrical stimulation produced approaches toward food and eating in the satiated state, without meowing or attempting to escape during a behavioral test. Basal gastric secretion was not increased during stimulation of the “feeding” sites, applied when the animals were hungry. In one of these cats electrical stimulation of another site, located in the anterior hypothalamus, produced an increase in acid secretion; cating was not evoked by stimulation of this site during the behavioral test. The present results seem to suggest that the hypothalamic regions related to gastric acid secretion are not identical to those related to eating.