Automaintenance in guinea pigs: effects of feeding regimen and omission training

Behavior maintained by stimulus-reinforcer pairings was examined. Guinea pigs maintained at 85 per cent of free-feeding weights reliably contacted a retractable lever presented before delivery of a single piece of guinea-pig chow or a 45-milligram guinea-pig pellet. When animals were given free access to one food and received the second food preceded by the lever, contact responses persisted. Such responses seldom occurred when a single food was freely available and was also delivered after lever presentation. Introduction of an omission training (negative automaintenance) procedure, in which lever contacts resulted in lever retraction and prevented food delivery, strongly reduced lever contacts. Observation indicated that mouthing the food cup, instead of the lever, became the prominent behavior during the prefood stimulus under the omission training procedure.     

Effects of prompting and reinforcement of one response pattern upon imitation of a different modeled pattern

Twelve preschool children participated in a study of the effects of explicit training on the imitation of modeled behavior. The responses trained involved a marble-dropping pattern that differed from the modeled pattern. Training consisted of physical prompts and verbal praise during a single session. No prompts or praise were used during test periods. After operant levels of the experimental responses were measured, training either preceded or was interposed within a series of exposures to modeled behavior that differed from the trained behavior. Children who were initially exposed to a modeling session immediately imitated, whereas those children who were initially trained immediately performed the appropriate response. Children initially trained on one pattern generally continued to exhibit that pattern even after many modeling sessions. Children who first viewed the modeled response and then were exposed to explicit training of a different response reversed their response pattern from the trained response to the modeled response within a few sessions. The results suggest that under certain conditions explicit training will exert greater control over responding than immediate modeling stimuli.     

Note on aversion learning to the shape of food by monkeys

Vervet and grivet monkeys were repeatedly tested eating bar- and circle-shaped cookies. One subject was always injected with lithium immediately after eating cookies with the circle shape and learned to avoid the circular cookies while continuing to eat the bar-shaped cookies. Another subject received similar treatment except that lithium injections were always delayed 30 minutes after access to the circle-shaped cookies. She also acquired a discriminative aversion. Aversion learning was not observed with 60-minute delayed toxicosis or with lithium injections administered unpaired with access to the cookies. The two types of cookies differed only in shape, and conditioning and test sessions were conducted in total darkness to preclude the use of visual cues. Therefore, the avoidance observed in subjects conditioned with immediate and 30-minute delayed toxicosis represents a conditioned aversion to the shape of the cookies as revealed by tactile cues. These findings illustrate that monkeys can learn to select food on the basis of tactile stimuli when such stimuli are conditioned with delayed aversive stimulation.     

Impact of outpatient non-myeloablative haematopoietic stem cell transplantation in quality of life vs. conventional therapy

The role of outpatient hematopoietic stem cell transplantation (HSCT) as a therapeutic tool has been strengthened significantly because of the increasing number of patients undergoing this treatment. Due the very nature of this procedure, one of the aspects that should not be overlooked is the quality of life (QOL) of patients undergoing HSCT. Thus, one must consider not only health status after treatment, but also, the psychosocial implications for the patient. This is an observational, longitudinal, and prospective study to assess QOL in patients undergoing outpatient HSCT vs. similar patients receiving medical treatment (MxTx). By applying the COOP/WONKA charts on five occasions (pre-HSCT/initial, post-HSCT/first month, and at 3, 6, and 9 months), thirty-eight patients were analysed, 19 with HSCT and 19 with MxTx with no differences in age, gender or diagnosis. The initial survey found significant differences only in pain perception, which was higher in the HSCT group (p = .08); at the first month, there was a greater tendency for feelings of depression or anxiety in the HSCT group (p = .016), with more limitations in social (p = .003) and daily (p = .044) activities. From 3 months post-HSCT, the results were very similar. The differences persisted only in the area of social activities. Four patients developed graft-versus-host disease with no significant difference in the scores obtained compared to other transplant patients at 3, 6, and 9 months (p = .26) of follow-up.     

Instrumental conditioning of aggressive behavior in rats

A method has been developed for bringing an aggressive response under stimulus control. It was found that the number of conditioned aggyessive responses was maximal when low-weight target rats were used. The latencies of the conditioned responses toward target animals of 124 gm were significantly lower than those toward animals of 221 and 284 gm. The application of an extinction procedure on the conditioned aggressive response substantially increased the total number of emitted aggressive responses.     

预期错误在恐惧记忆更新中的作用与机制

依据错误驱动的学习理论,行为预期结果与实际结果之间的不匹配即预期错误(Predictionerror,PE)是学习产生的驱动因素。作为显著性信息中的一种,预期错误和物理显著性、惊讶、新异性等存在信息加工阶段的不同,与记忆更新的关系也有差异。近年来,记忆再巩固干预范式(reconsolidation interference)被证明可用于人类条件性恐惧记忆的更新,其中记忆提取激活阶段所包含的预期错误起到了引发记忆“去稳定”、开启记忆再巩固的关键作用。在促进恐惧记忆更新的行为机制上,PE被认为是记忆去稳定的必要非充分条件。记忆提取必须包含适量的PE,但其引发的是记忆去稳定、消退还是中间状态,还需结合记忆本身性质确定。在促进恐惧记忆更新的神经机制上,杏仁核、导水管周围灰质(PAG)、海马均在PE探测和计算过程中具有重要作用;前额叶皮层(PFC)及其亚区在PE开启记忆再巩固过程中扮演了重要角色。上述过程又受到神经系统中特定神经递质的重要调节,尤其是多巴胺能和谷氨酸能。未来研究应进一步探索基于PE计算模型的量化研究,整合PE与其他边界条件的交互作用,考察不同类型显著性在记忆再巩固中的作用等;并亟...     

Learning strategies during fear conditioning

This paper describes a model of fear learning, in which subjects have an option of behavioral responses to impending social defeat. The model generates two types of learning: social avoidance and classical conditioning, dependent upon (1) escape from or (2) social subordination to an aggressor. We hypothesized that social stress provides the impetus as well as the necessary information to stimulate dichotomous goal-oriented learning. Specialized tanks were constructed to subject rainbow trout to a conditioning paradigm where the conditioned stimulus (CS) is cessation of tank water flow (water off) and the unconditioned stimulus (US) is social aggression from a larger conspecific. Following seven daily CS/US pairings, approximately half of the test fish learned to consistently escape the aggression to a neutral chamber through a small escape hole available only during the interaction. The learning curve for escaping fish was dramatic, with an 1100% improvement in escape time over 7 days. Fish that did not escape exhibited a 400% increase in plasma cortisol and altered brain monoamine response to presentation of the CS alone. Elevated plasma cortisol levels represent classical fear conditioning in non-escaping fish, while a lack of fear conditioning and a decreased latency to escape over the training period in escapers indicates learned escape.     

Evidence for associative learning in newly emerged honey bees (Apis mellifera)

The honey bee is a model organism for studies on the neural substrates of learning and memory. Associative olfactory learning using sucrose rewards is fast and reliable in foragers and older hive bees. However, researchers have so far failed to show any significant learning in newly emerged bees. It is generally argued that in these bees only part of the brain structures important for learning are fully developed. Here we show for the first time that newly emerged honey bees are capable of associative learning, if they are sufficiently responsive to sucrose. Responsiveness to sucrose, which can be measured using the proboscis extension response (PER), increases with age. Newly emerged bees are on average very unresponsive to sucrose. We show that if newly emerged bees displaying a PER to 10% sucrose or lower sucrose concentrations are conditioned to an odour, they show significant associative learning and early long-term memory. Nevertheless, the level of acquisition is still lower than in foragers. The general assumption that newly emerged honey bees are incapable of associative learning must therefore be reconsidered. Further, our study suggests that an age-dependent increase in responsiveness to rewarding stimuli is directly related to the development of early learning abilities. The decisive influence of responsiveness to rewarding stimuli in associative learning of newly emerged bees has far reaching consequences for studies on the development of associative learning capabilities in insects and vertebrates.     

TRANSFER OF AVERSIVE RESPONDENT ELICITATION IN ACCORDANCE WITH EQUIVALENCE RELATIONS

The present study investigates the transfer of aversively conditioned respondent elicitation through equivalence classes, using skin conductance as the measure of conditioning. The first experiment is an attempt to replicate Experiment 1 in Dougher, Augustson, Markham, Greenway, and Wulfert (1994), with different temporal parameters in the aversive conditioning procedure employed. Match‐to‐sample procedures were used to teach 17 participants two 4‐member equivalence classes. Then, one member of one class was paired with electric shock and one member of the other class was presented without shock. The remaining stimuli from each class were presented in transfer tests. Unlike the findings in the original study, transfer of conditioning was not achieved. In Experiment 2, similar procedures were used with 30 participants, although several modifications were introduced (formation of five‐member classes, direct conditioning with several elements of each class, random sequences of stimulus presentation in transfer tests, reversal in aversive conditioning contingencies). More than 80% of participants who had shown differential conditioning also showed the transfer of function effect. Moreover, this effect was replicated within subjects for 3 participants. This is the first demonstration of the transfer of aversive respondent elicitation through stimulus equivalence classes with the presentation of transfer test trials in random order. The latter prevents the possibility that transfer effects are an artefact of transfer test presentation order.     

Beyond awareness and resources: Evaluative conditioning may be sensitive to processing goals

Evaluative conditioning (EC) is often regarded as an automatic affective learning process. Yet, recent empirical evidence suggests that EC may actually be sensitive to contingency awareness and to the availability of attentional resources. Here, we examine for the first time a third horseman of EC automaticity: processing goals. Specifically, we had participants engage an EC task after completing a task known to elicit the goal of processing either the perceptual similarities or the perceptual differences between stimuli. EC was predicted and found to be larger in the former (similarity-focus) than in the latter (difference-focus) condition. This finding provides original evidence that EC is sensitive to the processing goal activated in participants as they encode the CS-US pairings. The theoretical implications of this finding are discussed.