RESUMEN

The purpose of this study was to determine whether an entire experimental situation, and not an individual single stimulus, could be employed to generate a conditioned response. Experiments were conducted on four adult cats. Each cat was conditioned in two different experimental environments (Situation I and Situation II), which consisted of two compartments that differed with respect to color, shape and illumination. Experiments were carried out separately on each cat; experimental sessions, which lasted 30 min, were conducted two or three times a week. Two cats (Nos. 1 and 2) were first trained during 15 sessions in Situation I, and then during 15 subsequent sessions in Situation II. During each session in Situation I, electrical stimulation, which was applied to the basal forebrain area (BFA), evoked a slow-wave EEG pattern; in addition, the animals would close their eyes and lie down (i.e., they exhibited typical presleep behavior). After three to five sessions, this behavior began to appear as soon as the cats were introduced into the experimental compartment, even before stimulation was applied. In a further series of sessions, the cats were placed for 15 sessions in Situation II, wherein stimulation was applied to the lateral hypothalamus (LH). Stimulation of the LH evoked a desynchronized EEG pattern that was accompanied by excitatory behavior. In the other two cats (Nos. 3 and 4), the animals were first trained for 15 sessions in Situation II; subsequently, they were trained for 15 sessions in Situation I. Finally, a test of cross-stimulation was performed. Stimulation of the BFA (which was previously used in Situation I) was applied, one time only, to cats 1 and 2 in Situation II; stimulation of the LH (which was previously used in Situation II) was applied, once only, to cats 3 and 4 in Situation I. In both cases, the animals did not exhibit any of the previously observed behavioral reactions or EEG patterns of activity. The preceding results confirm our hypothesis that, in each situation, a conditioned reaction was established in response to the totality of the experimental environment.

Asunto(s)

RESUMEN

Two Warsaw medical students, Jerzy Konorski and Stefan Miller, having read I.P. Pavlov's works on conditional reflexes, informed him in a 1928 letter that they had discovered a new type of conditioning. A previously neutral stimulus preceded the passive lifting of a dog's paw which then was followed by feeding; this stimulus then evoked the spontaneous raising of that paw. Pavlov responded informing them that their conditioning of motor responses expanded his theory of higher nervous activity, but that their conditioning paradigm-that they named CRII-did not differ fundamentally from the Pavlovian conditioning paradigm. The replication of the Warsaw experiment in Pavlov's laboratory failed to provide unequivocal results. From 1931 to 1933, Konorski, working in Pavlov's Leningrad laboratory, further explored the parameters of CRII. Pavlov insisted that the conditioning of motor movements differs from the conditioning of other sensory analyzers only in that, on the neural level, the motor analyzer is both afferent, that is, perceptive, and efferent, that is, responsive. Konorski was not convinced, and he subsequently maintained that the two conditioning paradigms were fundamentally different.

Asunto(s)

RESUMEN

Experiments were conducted on three chronic unanesthetized, undrugged cats. Electrical stimulation of the basal forebrain area (BFA) resulted in presleep behavior (i.e., the cats would sit or lie down, and EEG spindles would arise). After several sessions (conducted twice a week), two of these cats began to exhibit presleep behavior almost immediately after entering the experimental compartment, even before the application of BFA stimulation. The third cat often ate some food (which was always present in the compartment) before showing presleep behavior. When stimulation was withheld during an extinction procedure, the cats still exhibited presleep behavior in the absence of stimulation during several sessions. We conclude that repeated BFA stimulation led to conditioning of the stimulation effects, that is, the presleep behavior that was evoked by the environmental situation alone, without BFA stimulation or any other intermittent stimulus.

Asunto(s)

RESUMEN

This article describes the pioneer research of Jerzy Konorski on voluntary motor conditioned reflexes type II (CRIIs or instrumental CRs). Some of his publications on topics such as four varieties of CRIIs, switching, and ability of transformation (plasticity) of CRIIs are briefly summarized. Konorski's theoretical views including criticism of some of Pavlov's interpretations are also presented. A few events connected to Konorski's scientific activities are mentioned.

Asunto(s)

RESUMEN

This article reviews studies of various authors on the phenomenon of "switching," which is observed in both classical and instrumental conditioning and consists in elicitation of different responses to the same conditional stimulus (CS) when it is applied in an environment different than the original one. The different responses include a decrease or an absence of the previously trained conditional response (CR), elicitation of an appetitive response instead a defensive one, or vice versa, as well as elicitation of two different instrumental CRs in the same trial. The studies suggest that, due to the repeated occurrence of CS in the same environment (E), also called "situation" or "context," associations are formed between CS and E. Consequently, the CR is elicited to a compound CS+E rather than to CS alone. When the CS is applied alone in a different E than the original one, the previously formed associations are inactive and the CR cannot be elicited; this leads to switching. Studies also suggest that E plays a dominant role in conditioning compared with that of CS alone, which often appears to be only a trigger for eliciting the response. However, CS tested in a different E may still produce some components of the previously acquired CR, such as a general fear behavior to an originally defensive CS or an approach behavior to an originally alimentary CS. The environmental stimuli can be considered the "determining" stimuli that determine the kind of reaction to be elicited, or "tonic" stimuli that increase the tonus in the brain but do not elicit the CR. The "determining" or "tonic" stimuli do not seem to be a special class of stimuli. Instead, they are stimuli that initially can produce the CR (e.g., intertrial CRs), but by being not reinforced they become partly inhibited; nevertheless, due to associations with the reinforcement, they still can produce some excitement related to it, thus facilitating the CR.

Asunto(s)

RESUMEN

The purpose of this study was to answer the question as to whether the food preferences of the young are dependent on the social influences or not. The experiments were conducted on female cats bearing electrodes implanted in the mid-lateral hypothalamus, and their weanling kittens. Each mother was given a self-stimulation test; the mothers which learned to press a lever for the hypothalamic stimulation reward were chosen for the experiment. Each mother, always 4 h food deprived before the session, was given a choice of meat pellets and banana slices. Eating bananas was rewarded by the hypothalamic stimulation whereas eating meat pellets was not; as a result, the mother concentrated only on eating bananas while ignoring meat pellets. In the following sessions one or two weanling kittens were always accompanying the mother during the session. It was found that 15 out of 18 weanling kittens used in this experiment joined the mothers in eating bananas. After separation from the mothers these kittens continued to choose bananas and ignore meat pellets when tested in the absence of the mother. Control kittens of the same age, which were never trained with the mother, refused to eat bananas. Similar results were obtained with other mother-kittens groups in which mashed potatoes or plain jellied agar were given instead of bananas. These results suggested that the food preferences of the weanling kittens were influenced by the mother's choice of food, even in the case when this food was unusual for the species.

Asunto(s)

Asunto(s)

RESUMEN

This article reviews the results of experimental studies on imitative behavior reported by various investigators, and then discusses the possible brain mechanisms responsible for this behavior. It was found that human infants in their first hours of life were already capable of spontaneous imitation of simple motor acts demonstrated by an adult, without previous training or reward; these observations suggest that imitative behavior is an innate process that can be considered an unconditional reflex of imitation. It was also found that satiated animals resumed eating when they saw their companions eating. In the latter case, the imitative reflex triggered the previously acquired feeding behavior. Similar mechanisms could be responsible for the phenomenon of eating more in the presence of companions than in their absence, as well as that of preferring the food chosen by companions. When followed by a reward, the imitative act can be learned--that is, transformed into an instrumental conditional response; learning by imitation of simple motor acts was observed in animals, and that of complex motor acts was observed in children who had already achieved a certain developmental stage. In animals, learning complex motor tasks was facilitated by previous observation of a companion performing this task. In this case, the presence of the observer during the session could lead to habituation of the experimental situation and production of associations between this situation and stimuli or emotions related to the reward or punishment, and might result in more efficient learning later. The imitative behavior can be inhibited by stimuli producing responses antagonistic to the act of imitation.

Asunto(s)

RESUMEN

The purpose of this study was to gather anatomical data concerning sites for self-stimulation in the lateral hypothalamus in the cat. The study was conducted on 25 adult cats. In each cat, one to three monopolar stimulating electrodes were implanted bilaterally in the lateral hypothalamus in a region between sections Fr 10.0 and Fr 13.0, L 2.0 and L 5.0, and H -2.0 and H -6.0. A reference electrode was placed in the calvaria over the frontal sinus. Twenty-two of these cats learned to press a lever when each press was rewarded by a brief (0.3 s) electrical stimulus (2.0 to 7.0 V, 100/s, 1 ms duration per pulse) delivered to the hypothalamus. Postmortem anatomical analysis of the brains revealed that most of the positive rewarding sites were located in a midlateral hypothalamic zone, which included the medial forebrain bundle, and were localized to section Fr 11.5, between L 2.0 and L. 5.0, and H -3.0 and H -5.5.

Asunto(s)

RESUMEN

Thirsty cats, offered a choice between distilled water and quinine solution, preferred the latter to distilled water and accepted quinine concentrations greater than those they accepted in control sessions when drinking quinine solution was rewarded by hypothalamic stimulation, whereas drinking distilled water was not. When the same stimulation rewarded drinking distilled water only, the cats switched to distilled water and refused quinine solutions at concentrations even less than those previously accepted in control sessions. It was concluded that drinking quinine solution was an instrumental response which secured the desirable hypothalamic stimulation.

Asunto(s)

RESUMEN

Anorexia nervosa (AN) can be considered a result of complex instrumental conditioning. It is postulated that in healthy nonsatiated individuals, the sight and smell of the preferred food, acting as a conditioned stimulus (food CS), activates a memory pattern of associations "eating--desirable sensory input" (approach pattern). This leads to the instrumental reaction of eating which is reinforced by sensory satisfaction. In victims of AN, in addition to the approach pattern the food CS activates another pattern of associations consisting of such components as "eating--obesity--failure" and " noneating --thinness--success" (avoidance pattern). The establishment of the avoidance pattern depends on such factors as social preferences and pressures to be slim, inborn dispositions, and personal psychological problems. If the activation of the avoidance pattern prevails over the activation of the approach pattern, the individual refrains from eating. The refusal to eat is here an instrumental avoidance reaction; its performance is reinforced by satisfaction derived from successful self-control and losing weight. A prolonged activation of the avoidance pattern leads to malnutrition and ultimately to death. In cases in which the approach pattern and the avoidance pattern are frequently activated simultaneously to the same degree, a neural conflict may develop. In a variation called "bulimia nervosa," an activation of the approach pattern alternates with the activation of the avoidance pattern. First, overeating takes place; it is reinforced by oral-gastric satisfaction. Then, the avoidance reaction of self-induced vomiting or purging follows; it is reinforced by satisfaction derived from preventing weight gain.

Asunto(s)

RESUMEN

Social influences on drinking ethanol solution were studied in two cats ("drinkers") who voluntarily drank small amounts of 10% ethanol solution in milk and three other cats ("nondrinkers") who served as companions to the drinkers. A 15-minute session was conducted daily in a compartment divided into two even parts with a transparent Plexiglass partition. The cats were introduced to the compartment either singly or in pairs. Each pair consisted either of two drinkers or one drinker and one nondrinker. Each cat of the pair was placed in one part of the compartment; the cats could see each other, but they could not make physical contact. Each drinker was offered 10% ethanol solution in milk, while each nondrinker was given plain milk, and the amount of consumption was measured. A series of five to ten sessions with a drinker was followed by a series of sessions with a nondrinker or with no companion. There were a total of 13 series of sessions for each drinker. A statistical analysis of the data showed that, in most series, the mean amount of consumption of ethanol solution was significantly higher in the presence of a companion (either drinker or nondrinker) than in its absence.

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The mechanisms involved in avoidance behavior are discussed. It is assumed that the conditioned stimulus (CS) activates the memory pattern of associations related to the former applications of the unconditioned stimulus (US) and, as a result, produces an undesirable sensory state. This activates another memory pattern of associations related to the avoidance response and the postponement of the US. The performance of the avoidance response discontinues the CS, resulting in inactivation of the first memory pattern; this leads to a removal of the undesirable sensations, i.e., to an improvement in the sensory state. It is suggested that avoidance behavior obeys the same general rules which apply to approach (appetitive) behavior. In both approach and avoidance behavior the instrumental response provides a desirable sensory change (due to obtaining of the desired US in approach behavior and the postponement of the undesired US together with the discontinuation of CS in avoidance behavior). In 'both cases the response gradually extinguishes when its performance no longer provides the sensory "better-being".

Asunto(s)

RESUMEN

Experiments were carried out on cats fitted with a gastric fistula. In one group of 6 cats basal gastric secretion, and in another group of 7 cats pentagastrin induced gastric secretion was collected two or three times a week during a 2 hr session. The sessions were conducted either in a "harness" situation where the cat's movements were restricted, or in a "cage" situation where the cat was unrestricted and could move freely. It was found that in four of 6 cats in the basal secretion group and in five of 7 cats in the pentagastrin induced secretion group, gastric acid output was significantly higher in sessions in harness than in sessions in cage. These differences in acid output were due to acidity rather than volume of secretion. It was hypothesized that restriction of the animal's movements in the harness could evoke a "reflex of freedom" which, however, could not be accomplished because of the confinement. This could evoke a neural conflict eventually leading to functional disturbances in the autonomic system. This, in turn, resulted in changes in gastric acid secretion.

Asunto(s)

Asunto(s)

Asunto(s)