Conditioned visual flight orientation in Drosophila: dependence on age, practice, and diet.
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Orientation preferences for visual patterns can be conditioned in tethered flies (Drosophila melanogaster) at the flight simulator. In a reversal conditioning procedure using heat as reinforcement, flies can be trained to successively prefer different flight orientations with respect to the patterns. As in many learning paradigms, conditioned responses are highly variable. Although during training most flies reliably avoid the heat and the corresponding flight orientations, in subsequent learning tests without heat some show no consistent preference for the permissive orientations. We have started to investigate the interindividual differences in learning performance and describe here three significant variables: the age of the animals, their experience in the flight simulator prior to the experiment, and the composition of the fly food. Flies learn more reliably at 3-4 days than at 1-2 days of age but learning indices do not increase further in even older flies. Learning is improved if flies are allowed to become familiar with the flight simulator before the start of the conditioning procedure. Most important, poor nutrition causes complete amnesia within three or four generations. The reverse shift from poor to nutritious food restores learning ability with an even longer delay. (+info)
Nonassociative and associative modification of head-waving produced by aversive tentacular stimuli in Aplysia.
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Head-waving, a spontaneously occurring exploratory and appetitive behavior of the marine mollusc Aplysia, provides an opportunity to examine mechanisms of learning expressed in a nonreflexive behavior. The present study explores nonassociative and associative forms of learned modification of head-waving produced using an aversive stimulus as reinforcement. Experiments on intact, freely behaving animals demonstrate that training with electric shock as an aversive unconditioned stimulus, delivered unilaterally to the anterior tentacles, produces a learned shift in head-waving behavior away from the side on which shock was applied. This behavioral change is a novel learned behavioral response that is influenced by the topographic location of an aversive stimulus. Furthermore, training with application of tentacle shock reinforcement, contingent upon the animal's head position, produces operant conditioning of head-waving. Thus, anterior tentacle shock is effective as an aversive reinforcer for both nonassociative and operant learning expressed in the head-waving behavior of Aplysia. (+info)
Conditioning method dramatically alters the role of amygdala in taste aversion learning.
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Although an important role for the amygdala in taste aversion learning has been suggested by work in a number of laboratories, results have been inconsistent and interpretations varied. The present series of studies reevaluated the role of the amygdala in taste aversion learning by examining the extent to which conditioning methods, testing methods and lesioning methods, influence whether amygdala lesions dramatically affect conditioned taste aversion (CTA) learning. Results indicated that when animals are conditioned with an intraoral (I/O) taste presentation, lesions of amygdala eliminate evidence of conditioning whether animals are tested intraorally or with a two-bottle solution presentation. Dramatic effects of amygdala lesions on CTA learning were seen whether lesions were made electrolytically or using an excitotoxin. In contrast, when animals were conditioned using bottle presentation of the taste, electrolytic lesions attenuated CTAs but did not eliminate them, and excitotoxic lesions had no effect. These results are consistent with the hypothesis that neural structures critical for CTA learning may differ depending on the extent to which the method of conditioned stimulus delivery incorporates a response component. (+info)
How pigeons discriminate the relative frequency of events.
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This study examined how pigeons discriminate the relative frequencies of events when the events occur serially. In a discrete-trials procedure, 6 pigeons were shown one light nf times and then another nl times. Next, they received food for choosing the light that had occurred the least number of times during the sample. At issue were (a) how the discrimination was related to two variables, the difference between the frequencies of the two lights, D = nf - nl, and the total number of lights in the sample, T = nf + nl; and (b) whether a simple mathematical model of the discrimination process could account for the data. In contrast with models that assume that pigeons count the stimulus lights, engage in mental arithmetic on numerons, or remember the number of stimuli, the present model assumed only that the influence of a sample stimulus on choice increases linearly when the stimulus is presented, but decays exponentially when the stimulus is absent. The results showed that, overall, the pigeons discriminated the relative frequencies well. Their accuracy always increased with the absolute value of the difference D and, for D > 0, it decreased with T. Performance also showed clear recency, primacy, and contextual effects. The model accounted well for the major trends in the data. (+info)
Value transmission in discrimination learning involving stimulus chains.
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Rats learned a series of reversals of a positional discrimination in which responses to one lever led to delayed food and responses to a second lever led to no food. Interpolated within the delays leading to the different outcomes were two-link stimulus chains. The pairing of each stimulus element with the delayed outcome of food or no food varied across reversals. Either stimulus element could have the same correlation with outcome as occurred on the preceding reversal or the opposite correlation as on the preceding reversal. New reversals were acquired more quickly when both stimulus elements had the same status as during the preceding reversal, and were acquired most slowly when both stimulus elements had the opposite status as that of the preceding reversal. The rate of learning was intermediate when only one of the stimulus elements had the same status as that during the preceding reversal. All of the data are compatible with an interpretation in terms of backward chaining of stimulus value. (+info)
Philosophical behaviorism: a review of things that happen because they should: a teleological approach to action, by Rowland Stout.
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Mentalistic terms such as belief and desire have been rejected by behavior analysts because they are traditionally held to refer to unobservable events inside the organism. Behavior analysis has consequently been viewed by philosophers to be at best irrelevant to psychology, understood as a science of the mind. In this book, the philosopher Rowland Stout argues cogently that beliefs and desires (like operants such as rats' lever presses) are best understood in terms of an interaction over time between overt behavior and its overt consequences (a viewpoint called teleological behaviorism). This book is important because it identifies the science of the mind with the science of overt behavior and implies that the psychologists best equipped to study mental life are not those who purport to do so but those who focus on the experimental analysis of behavior. (+info)
Operant responding for ethanol in rats with a long-term history of free-choice ethanol drinking.
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Wistar rats were allowed to drink ethanol in a two-bottle (water vs 2-8% v/v ethanol) and then in a three-bottle choice paradigm (water vs 8% ethanol vs 16% ethanol, v/v). After 7 months of free access to alcohol, the subjects were trained to respond for 8% ethanol in an operant procedure. No relationship was found between prior alcohol drinking and lever pressing for ethanol. (+info)
Long-term effects of postovulatory aging of mouse oocytes on offspring: a two-generational study.
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Aims of this study were to analyze the long-term effects of postovulatory aging of mouse oocytes on 1) reproductive traits of parental (F(0)) and first (F(1))-generation females (pregnancy rate, gestation length, litter size, perinatal death, and sex ratio of offspring) and 2) developmental and behavioral variables of F(1) and second-generation (F(2)) offspring (birth weight and weight gain during preweaning development, postnatal day of attainment of immediate righting, spontaneous motor activity, and passive and active conditioned learning ability). Hybrid (C57BL/6JIco x CBA/JIco) females were artificially inseminated at 13 h (control group) or 22 h (oocyte-aged group) after GnRH injection. Experimental (oocyte-aged group) F(0) females exhibited lower pregnancy rate, shortened gestation length, decreased litter size, higher perinatal death of their pups, and increased percentage of male offspring compared to control F(0) females. Postovulatory aging of oocytes was also associated with increased number of growth-retarded pups, delayed development of the righting reflex, and higher spontaneous motor activity and emotionality of F(1) offspring. Postovulatory aging of F(0) oocytes did not affect birth weight, weight gain during preweaning development, passive and active conditioned learning ability of F(1) offspring, or reproductive traits of F(1) females or developmental and behavior variables of F(2) offspring. (+info)