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Apontamentos para o estudo do desamparo aprendido
Abstract
O presente texto destaca alguns aspectos conceituais, metodológicos e teóricos relacionados ao estudo do desamparo aprendido com o objetivo de nortear o pesquisador iniciante no tema. Essas considerações são fundamentadas em trabalhos experimentais com sujeitos não humanos, formuladas a partir da perspectiva comportamentalista radical. São abordados criticamente os conceitos de controle e incontrolabilidade, o delineamento experimental triádico que caracteriza essas pesquisas, a definição do efeito comportamental em estudo, as principais hipóteses explicativas e a sua proposição como modelo animal de depressão. Algumas hipóteses alternativas são também apontadas em função do seu potencial de incentivo para novos estudos. Dois problemas encontrados nos estudos da área são destacados: 1) a suposição da “expectativa” como variável independente e 2) o uso ambíguo do termo “desamparo aprendido”, tanto para designar o efeito comportamental como uma das hipóteses que o explicam. Espera-se que o texto contribua para que analistas do comportamento iniciantes possam estabelecer procedimentos e interpretações rigorosos dos resultados obtidos, possibilitando o avanço na compreensão do desamparo aprendido. Palavras-chave: Desamparo aprendido, controle, incontrolabilidade, modelo animal, depressão.
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Este estudo investigou se a exposição a diferentes contingências de reforçamento positivo, antes do tratamento com choques incontroláveis, pode impedir o desenvolvimento do desamparo aprendido em ratos (efeito de imunização). Foram manipulados cinco grupos de ratos Wistar (n= 8). Sujeitos de três grupos foram submetidos a sessões de reforçamento positivo (CRF, FR6 ou múltiplo-concorrente FR 6/Extinção), seguidas de uma sessão de choques incontroláveis e outra de teste de fuga. Sujeitos de outro grupo foram expostos apenas a sessões de choques incontroláveis e teste de fuga, sendo que os animais do grupo restante foram expostos apenas à sessão de teste de fuga. Os resultados no teste mostraram que apenas os animais submetidos previamente aos choques incontroláveis apresentaram dificuldade na aprendizagem de fuga (desamparo aprendido). Contudo, aqueles expostos inicialmente ao reforçamento positivo tiveram reduzido o efeito dos choques incontroláveis, independente da contingência utilizada. Esses resultados sugerem que a exposição repetida ao reforçamento positivo pode produzir o efeito de imunização.
Palavras-chave: desamparo aprendido; efeito de humanização; controle aversivo.
Foram realizados dois experimentos com o objetivo de investigar o desamparo aprendido e a imunizaçâo, em ratos, em funçâo do nível de atividade motora da resposta a ser aprendida: "saltar" e "focinhar", classificadas como de alta e baixa atividade, respectivamente. No experimento 1, os animáis foram subrnetidos a duas sesssões, sendo na primeira expostos a choques incontroláveis ou nenhum choque, e na segunda submetidos a urna contingéncia de fuga com as respostas de saltar ou focinhar. No experimento 2, os sujeitos foram submendos a trĕs sessões: na pnmeira receberam choques controláveis (resposta de focinhar), choques incontroláveis ou nenhum choque; na sesssâo seguinte, metade dos animais de cada grupo foi exposta a choques incontroláveis e metade a nenhum choque; na terceira sesssâo, todos os animais foram submetidos a urna contingĕncia de fuga com a resposta. de saltar. Os resultados mostraram dificuldade de aquisiçáo da resposta de fuga em todos os grupos previamente expostos a choques incontroláveis (desamparo), mas a primeira experiĕncia prévia com controle impediu o aparecimento deste efeito (imunizaçáo). Os resultados mostraram igual nível de desamparo nos testes com respostas de alta e baixa atividade motora. Além disso, o treino de fuga com resposta pouco ativa imunizou os sujeitos contra o desamparo. Estes resultados sâo discutidos considerando-se as hipóteses do desamparo aprendido e da inatividade aprendida.
Uncontrollable stress can have a profound effect on an organism's ability to respond effectively to future stressful situations. Behavior subsequent to uncontrollable stress can vary greatly between individuals, falling on a spectrum between healthy resilience and maladaptive learned helplessness. It is unclear whether dysfunctional brain activity during uncontrollable stress is associated with vulnerability to learned helplessness; therefore, we measured metabolic activity during uncontrollable stress that correlated with ensuing inability to escape future stressors. We took advantage of small animal positron emission tomography (PET) and 2-deoxy-2[¹⁸F]fluoro-D-glucose (¹⁸FDG) to probe in vivo metabolic activity in wild type Sprague Dawley rats during uncontrollable, inescapable, unpredictable foot-shock stress, and subsequently tested the animals response to controllable, escapable, predictable foot-shock stress. When we correlated metabolic activity during the uncontrollable stress with consequent behavioral outcomes, we found that the degree to which animals failed to escape the foot-shock correlated with increased metabolic activity in the lateral septum and habenula. When used a seed region, metabolic activity in the habenula correlated with activity in the lateral septum, hypothalamus, medial thalamus, mammillary nuclei, ventral tegmental area, central gray, interpeduncular nuclei, periaqueductal gray, dorsal raphe, and rostromedial tegmental nucleus, caudal linear raphe, and subiculum transition area. Furthermore, the lateral septum correlated with metabolic activity in the preoptic area, medial thalamus, habenula, interpeduncular nuclei, periaqueductal gray, dorsal raphe, and caudal linear raphe. Together, our data suggest a group of brain regions involved in sensitivity to uncontrollable stress involving the lateral septum and habenula.
Learning and Complex Behavior is a book that describes basic biobehavioral processes and explores their implications for complex human behavior. Basic processes (4 chapters) include natural selection, selection by reinforcement, generalization, discrimination, conditioned reinforcement, schedules of reinforcement, and associated phenomena. Complex behavior (8 chapters) includes stimulus classes (“concepts”), attending, perceiving, remembering, imagining, problem solving, and verbal behavior together with related findings from neuroscience and neuropsychology. The website complements—but does not replace—the book. If you are considering purchase of the book, select the button labeled To buy book.
Supplemental material is added to the web site from time to time to keep the book current and to address additional topics. A complete listing of supplemental material is available by selecting the button labeled Supplemental Material. Because the principles rest upon well-established experimental findings, new findings in the Supplemental Material do not alter the approach fundamentally but permit their implications to be pursued more fully. The supplementary material for a given chapter is accessible through the web page for that chapter. Republishing the original book and adding supplemental material on the web site also has a practical value: It provides an updated and expanded book at approximately one-third the cost of a revised edition by the original commercial academic publisher. See http://lcb-online.org/ for more information
O objetivo do trabalho foi testar a hipótese de que a interpretação do tempo de imobilidade (desamparo aprendido ou adaptação) pode variar conforme o modelo utilizado (teste da natação forçada ou estresse por natação). Foram analisados o tempo de imobilidade (TI) e a mobilização de glicogênio de ratos submetidos à natação em dois protocolos: estresse por natação (EN) e teste da natação forçada (TNF). Também comparamos os efeitos da desipramina e diazepam. Os experimentos foram filmados para análise do TI. Os ratos, após a sessão de natação, foram sacrificados e amostras do fígado e músculos foram preparadas para quantificação do glicogênio. O TI foi menor no EN comparado ao TNF (p=0,001). As concentrações de glicogênio hepático dos grupos foram diferentes entre si (controle>EN>TNF; p<0,05). Nos músculos gastrocnêmio e sóleo, as concentrações de glicogênio foram menores no EN comparado ao controle e TNF (p<0,05). O TI do grupo tratado com desipramina e diazepam também foi mensurado. A desipramina diminuiu o TI no TNF, sem alterá-lo no EN. O diazepam aumentou o TI no EN sem alteração no TNF. Concluímos que o EN e o TNF induziram respostas fisiológicas e comportamentais distintas e representam situações diferentes para o animal.
Embora a literatura relativa à análise do comportamento descreva as relações que envolvem controle aver-sivo, esse termo não é, em si, defi nido claramente. O presente texto visa analisar conceitualmente o que signifi ca “controle” e que fatores o caracterizam como “aversivo”. O termo “controle” é analisado funcio-nalmente, considerando-se as probabilidades relacionais envolvidas nas relações operantes e respondentes. Destaca-se a característica de bi-direcionalidade do controle na interação organismo/ambiente, o que ca-racteriza essa relação como dinâmica e responsável pela renovação contínua do comportamento e pela sua individualidade. A análise dos fatores que caracterizam o controle é feita a partir das operações e seus efeitos comportamentais, bem como da natureza dos estímulos envolvidos nas relações nomeadas como aversi-vas. Conclui-se que nenhum desses fatores permite a caracterização objetiva do agrupamento das relações aversivas. Sugere-se que o maior desenvolvimento de estudos experimentais sobre respondentes encobertos (respostas “emocionais”) pode ser um fator que ajude a tornar mais objetiva essa classifi cação.
Reviews the literature which examined the effects of exposing organisms to aversive events which they cannot control. Motivational, cognitive, and emotional effects of uncontrollability are examined. It is hypothesized that when events are uncontrollable the organism learns that its behavior and outcomes are independent, and this learning produces the motivational, cognitive, and emotional effects of uncontrollability. Research which supports this learned helplessness hypothesis is described along with alternative hypotheses which have been offered as explanations of the learned helplessness effect. The application of this hypothesis to rats and man is examined. (114 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Reviews S. F. Maier and M. E. Seligman's (see PA, Vol 56:Issue 1) learned helplessness hypothesis and uses a 2-process reinforcement theory to explain 5 "critical" studies which Maier and Seligman stated were unanswerable from an S-R (stimulus-response) position. (27 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Presents a behavioral analysis of depression which includes a discussion of avoidance, escape, and reinforcement parameters. The decreased frequency of many kinds of positively reinforced activity is seen as the common denominator among depressed persons. Basic behavioral processes which contribute to or reduce the frequency of a person's conduct are discussed, including changes in the environment, schedules of reinforcement, and suppressed anger. Implications of a behavioral analysis for research and verbal interaction with the therapist are discussed. It is concluded that behavioral and clinical concepts can be combined as a method of uncovering the actual events of psychopathology and therapy. (16 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Three experiments, with a total of 112 male albino Holtzman rats, explored whether inescapable shock of long duration and moderate intensity (LoShk) produces an avoidance-escape deficit (interference effect) by causing animals to learn to respond less actively or by causing them to learn to be "helpless." Exp I shows that if Ss given LoShk were subsequently tested in an avoidance-escape "nosing" response that required little motor activity, they learned and performed better than no-shock controls. Exp II verified that the same LoShk treatment that led to this better performance would indeed interfere with subsequent avoidance-escape acquisition in those test situations that have previously been used to demonstrate the interference effect, that is, the 3-response leverpress, 2-response shuttle, and single-response barrier jump. In Exp III, using triplets in the classical avoidance-escape, yoked, and control animal paradigm, it was shown that yoked Ss performed more poorly than either avoidance-escape or control Ss on a subsequent 3-response leverpress task but performed better on the nosing avoidance-escape task. Results are compatible with the idea that animals acquire the tendency to be inactive as a result of exposure to long-duration, moderate-intensity, inescapable shock. Results are incompatible with the idea that animals learn "helplessness." (20 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
2 experiments demonstrated that the effects of prior exposure to inescapable shock on the subsequent acquisition of an escape response in rats is determined by the nature of the contingency that exists between responding and shock termination during the escape learning task, and not by the amount of effort required to make the response or the amount of shock that the S is forced to receive during each trial. Exp I, using 48 male Simonsen rats, showed that inescapably shocked Ss did not learn to escape shock in a shuttle box if 2 crossings of the shuttle box were required (fixed ratio, FR, -2) to terminate shock, but did learn this FR-2 response if a brief interruption of shock occurs after the 1st crossing of the FR-2. Exp II with 72 Ss showed that inescapably shocked Ss learned a single-crossing escape response as rapidly as did controls, but were severely retarded if a brief delay in shock termination was arranged to follow the response. Results are discussed in terms of the learned helplessness hypothesis, which assumes that prior exposure to inescapable shock results in associative interference. (15 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Notes that learned helplessness-the interference with instrumental responding following inescapable aversive events-has been found in animals and man. The present study tested for the generality of the debilitation produced by uncontrollable events across tasks and motivational systems. 4 experiments with a total of 96 college students were simultaneously conducted: (a) pretreatment with inescapable, escapable, or control aversive tone followed by shuttlebox escape testing; (b) pretreatment with insoluble, soluble, or control discrimination problems followed by anagram solution testing; (c) pretreatments with inescapable, escapable, or control aversive tone followed by anagram solution testing; and (d) pretreatments with insoluble, soluble, or control discrimination problems followed by shuttlebox escape testing. Learned helplessness was found with all 4 experiments: Both insolubility and inescapability produced failure to escape and failure to solve anagrams. It is suggested that inescapability and insolubility both engendered expectancies that responding is independent of reinforcement. The generality of this process suggests that learned helplessness may be an induced "trait." (24 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
RESUMO – O desamparo aprendido tem sido definido como a dificuldade de aprendizagem apresentada por indivíduos que tiveram experiência prévia com estímulos aversivos incontroláveis. O objetivo deste trabalho é fazer uma revisão crítica dos estudos sobre o desamparo aprendido, com animais. Nessa análise, são considerados aspectos conceituais e metodológicos dos estudos em questão e as interpretações teóricas sobre esse efeito comportamental. Aborda-se a evolução histórica desses estudos, bem como alguns aspectos controversos das publicações que se acumularam ao longo de quatro décadas de pesquisa. A associação do desamparo aprendido com a depressão clínica é analisada criticamente, destacando-se a necessidade de maior rigor metodológico e conceitual nos estudos da área. Palavras-chave: desamparo aprendido; depressão experimental; controle aversivo; modelo animal de depressão.
A three-phase investigation of the effects of duration and number of inescapable shocks with rats was conducted. In the first
phase (shock treatment), separate groups were exposed either to 64 or 128 5-sec shocks or to 32, 64, or 128 10-sec shocks.
Measures of intrashock activity were found to be lower for the groups exposed to 64 or 128 10-sec shocks than for any other
group. In the second phase (Test Day 1), half of each group was tested for interference with FR 1, locomotor escape-avoidance
learning at either 24 or 168 h following cessation of shock treatment, using a control procedure that was designed to equate
groups for exposure to test shock. The results indicated that, relative to nonshock-treated controls, at each interval only
the groups previously given 64 or 128 10-sec shocks were impaired in terms of escape frequency. However, all groups given
at least 64 shocks exhibited depressed intertrial responding at the 24-h, but not the 168-h, interval. In the final phase
(Test Days 2–4), the control procedure for equalizing test-shock exposure was discontinued and a pattern of interference effects
was observed in terms of escape-avoidance response latency that was identical to that reported for the escape frequency in
Phase 2. In general, these data were viewed as indicating that duration, but not total amount of shock, was a critical determinant
of behavior during inescapable shock and of the subsequent interference effect. Both effects of duration were regarded as
the product of a common associative process involving the learning of immobility tendencies to shock that served to compete
with later escape-avoidance responding.
In these experiments we examined discrimination learning in a water escape task following exposure to escapable, yoked inescapable, or no electric shock. Inescapable shock did not have an effect on swim speeds in any of the experiments. Inescapable shock interfered with the acquisition of a position (left-right) discrimination when an irrelevant brightness cue (black and white stimuli) was present. However, inescapable shock did not affect the acquisition of the position discrimination when the irrelevant brightness cue was removed. Inescapably shocked subjects showed facilitated learning relative to escapably shocked and nonshocked subjects when the brightness cue was included as a relevant cue. These data may resolve discrepancies between studies that did, and did not, find inescapable shock to interfere with the acquisition of discriminations. Moreover, they point to attentional processes as one locus of the cognitive changes produced by inescapable shock and suggest that exposure to inescapable shock biases attention away from "internal" response-related cues toward "external" cues.
Dogs were given discriminative Pavlovian fear conditioning to 2 tones; 1 was consistently reinforced with shock, the other was never reinforced. Prior to or subsequent to Pavlovian conditioning, Ss received instrumental avoidance-training to a visual signal. After Ss had reached an avoidance learning criterion and received Pavlovian conditioning, extinction test trials to all 3 stimuli were given. All Ss demonstrated immediate, discriminative transfer of control of the avoidance response. However, discriminativeness and persistence of transfer test responding were greatly influenced by whether Pavlovian conditioning had preceded or followed instrumental avoidance training. Control groups delimited conditions for obtaining immediate, discriminative transfer of control of avoidance responding.
The psychological syndrome of learned helplessness is a uniquely modern phenomenon, deeply rooted in cultural concepts of personal power and security. This timely and valuable work examines learned helplessness with reference to the salient emphases in contemporary culture of individuality and personal control. An indispensable reference of interest to a broad spectrum of researchers in psychology.
Acceptance and commitment therapy (ACT) is one of several new cognitive and behaviour therapies that are now being referred to as the ?third wave? of behaviour therapy. It seeks to promote acceptance of unwanted private experiences through the application of various mindfulness strategies. This chapter tries to show the application of ACT treatment to the case of Gail, a 48-year-old woman with a long history of repeated episodes of depression. First, it introduces a case conceptualization framework that helps to ?describe? Gail's strengths and weaknesses from an ACT perspective. The chapter then demonstrates various ACT interventions suggested by the case conceptualization process. It also describes how an ACT therapist would adjust course on the basis of Gail's response (or lack of response) to an ACT clinical intervention. Finally, the chapter explains that there are obviously many nuances in the application of ACT that cannot be properly addressed.
Aversive events occur frequently in the life histories of all organisms. Long-lasting behavior pecularities, emotional illnesses, and anomalies of perception and thinking are attributed to such events. Apart from genetic or constitutional variables that might lead to individual differences in reactivity to aversive stimuli, there are a host of environmental variables that help to understand such individual differences. Two such environmental variables are the predictability and controllability of aversive events. This chapter reviews some of the behavioral and physiological consequences of aversive events that are either unpredictable, uncontrollable by a subject, or both. Unpredictable painful events turn out to be more distressing than are predictable ones. They generate more ulcers and intensify subjective reports of painfulness and anxiety. Both people and animals choose, if given the choice, predictable painful events over unpredictable ones. Uncontrollable painful events can interfere with an organism's ability later to solve problems to escape or avoid these events. They can lead to a phenomenon labeled “helplessness.” The chapter discusses the current status of research and theory concerning these phenomena. It describes a two-dimensional representation of the operations involved in instrumental training and Pavlovian conditioning. The chapter further reviews a number of theoretical interpretations of the effects of uncontrollable shocks on subsequent escape/avoidance learning and discusses the theoretical interpretations of the effects of unpredictable shocks on behavioral and physiological responses: the preparatory response hypothesis and the safety signal hypotheses.
Resumo: O desamparo aprendido pode ser deinido como uma diiculdade de aprendizagem encontrada em sujeitos que tiveram uma história prévia com estímulos incontroláveis. No estudo desse fenômeno com humanos, alguns aspectos especíicos relacionados ao controle experimental podem interferir na obtenção e na análise dos dados, entre eles: o estímulo em-pregado na fase de tratamento, a tarefa utilizada na fase de teste (geralmente a resolução de anagramas) e, inalmente, a condição de incontrolabilidade e as questões éticas relacionadas a ela. Estes aspectos foram discutidos criticamente no presente trabalho, considerando suas implicações na análise dos dados. Palavras-chave: desamparo aprendido em humanos, questões metodológicas, anagramas, questões éticas.
Abstract: Learned helplessness can be deined as a diiculty in learning found in subjects who had a history with uncontrollable stimuli. In the study of this phenomenon in humans, some speciic aspects related to experimental control can interfere with the data acquisition and data analysis. hose aspects are: the stimulus employed in pretreatment; the task used in testing (generally anagram solution testing); and, inally, the uncontrollability condition and its ethical issues. hose aspects were critically discussed in this article, taking into account their implica-tions for data analysis.
Presents an animal model of how learned helplessness may manifest itself as depression and anxiety. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
A series of four experiments investigated a number of parameters reported to produce “helplessness” in rats. Consistent differences
in escape behavior were not found between inescapably shocked and restrained rats when a FR 1 shuttling response was used.
Escape latencies also did not differ between groups when a reduced shock intensity was employed during escape training in
FR 2 procedure or when an increased FR 3 response was employed during escape training. Findings are discussed in terms of
the robustness of the failure-to-escape phenomenon from which “helplessness” in the rat is inferred.
Interference with shuttle-box escape learning following exposure to inescapable shock is often difficult to obtain in rats. The first experiment investigated the role of shock intensity during escape training in the apparent fragility of the effect. Experiment 1A demonstrated that the magnitude of the interference effect was systematically related to shock intensity during shuttle-box testing. At .6 mA, a robust effect was obtained, whereas at .8 mA and 1.0, little or no deficit in the escape performance of inescapably shocked rats was observed. Experiment 1B demonstrated that the deficit observed in Experiment 1A depended upon whether or not rats could control shock offset. Experiment 2 suggested that preshock may suppress activity and that higher shock levels may overcome this deficit. Experiment 3 tested this as the sole cause of the escape deficit by requiring an escape response which exceeded the level of activity readily elicited by a 1.0-mA shock in both restrained and preshocked rats. In such a task, preshocked rats performed more poorly than did restrained controls. These results are consistent with the possibility that inescapable shock may, in addition to reducing activity, produce an associative deficit. Experiment 4 more clearly demonstrated that inescapable shock produces deficits in performance which cannot be expleined by activity deficits and which appear to be associative in nature. It was shown that inescapable shock interfered with the acquisition of signaled punishment suppression but not CER suppression. The theoretical implications of these data for explanations of the manner in which prior exposure to inescapable shock interferes with escape learning were discussed.
The present experiments were designed to study the influence of prediction and control of electric shocks on various aspects of immune function, and the possible intermediate role of glucocorticoid hormones. After two sessions of inescapable footshocks, the reactivity of splenocytes to concanavalin A was reduced by one third, This effect was completely reversed when each shock was preceded by a warning stimulus, even though the adrenocortical response was the same in both conditions. In another experiment, rats were submitted to ten sessions of continuous avoidance in a shuttle-box and a group of yoked animals received the same footshocks without any relationship to their shuttling behavior. Although yoked rats displayed a reduced reactivity of splenocytes to lectins, animals of the avoidance group had a reduced antibody response to sheep erythrocytes. In contrast, no difference was observed in the corticosterone or prolactin response. These data further support the importance of psychological factors on stress-induced changes in immune functions. Furthermore, they demonstrate that various aspects of the immune system are differentially affected by behavioral factors and the results argue against a major role for the adrenocortical system in mediating these changes.
1. Three sets of criteria are proposed for assessing animal models of human mental disorders: predictive validity (performance in the test predicts performance in the condition being modelled), face validity (phenomenological similarity) and construct validity (theoretical rationale).2. The problems inherent in each of these validation procedures are discussed, and their application to the learned helplessness model of depression is examined.3. It is concluded that whilst the model has good predictive validity, important questions about face validity remain unanswered, and construct validity has not yet been established.4. The distinctions between animal models and some related experimental procedures are also discussed.
Three experiments investigated the effects of restraint and of inescapable fixed duration preshocks on subsequent shuttlebox escape-from-shock learning. Fixed-intensity preshock, random-intensity preshock, and no-preshock conditions were included in each experiment. In Experiment 1, restraining the rat in a harness prior to escape training retarded escape acquisition. There was no effect of preshock. In Experiment 2, both restraint and high fixed-intensity (1.0 mA) preshock retarded escape acquisition, when escape training occurred either immediately or 24 hr after preshock. In Experiment 3, movement was punished by positively correlating preshock intensity with the rat's movement; this treatment retarded escape conditioning. No effects were found for low fixed-intensity or random-intensity preshock nor for a condition in which movement was rewarded during preshock. The retarding effects of restraint and certain types of preshock were explained in terms of interfering instrumental responses.
Eighteen animal models of depression are reviewed in relation to three sets of validating criteria. Of the 18 models, five could only be assessed for predictive validity, seven could be assessed for predictive and face validity, and six could potentially have predictive, face and construct validity. Some traditional models (reserpine reversal, amphetamine potentiation) are rejected as invalid; the models with the highest overall validity are the intracranial self-stimulation, chronic stress and learned helplessness models in rats, and the primate separation model.
Rats were given series of escapable shocks, identical inescapable shocks, or no shock. The subjects were reexposed to a small
amount of shock 24 hours later, after which an in vitro measure of the cellular immune response was examined. Lymphocyte proliferation
in response to the mitogens phytohemagglutinin and concanavalin A was suppressed in the inescapable shock group but not in
the escapable shock group. This suggests that the controllability of stressors is critical in modulating immune functioning.
Exposure to painful or stressful stimuli produces an analgesic reaction which can persist for 1-2 h post-stress. In the typical stress-induced analgesia study the subject is not permitted to alter or exert control over the aversive event to which it is exposed. That is, its behavior affects neither the duration or intensity of the event. The experiments reported here attempted to determine whether this inability of the subject to control the aversive event is an important determinant of stress-induced analgesia, or whether simple exposure to painful events is a sufficient condition for its production. In the first experiment rats were given either escapable electric shocks (the subject's behavior could terminate the shock), equal amounts of inescapable shock, or no shock. Tail-flick to radiant heat was assessed 30 min later. The group given inescapable shock was strongly analgesic, while the group given an equal amount of escapable shock was only mildly analgesic. Thus the controllability of the shock or the availability of a coping response determined the antinociceptive reaction which followed. The second experiment revealed that this differential effect of controllability on tail-flick responding is masked, shortly after the end of the shock session, by a transient analgesic effect of shock which is not sensitive to the controllability dimension. The implications of these results for stress-induced analgesia and the activation of opioid systems are discussed.
Selection by consequences is a causal mode found only in living things, or in machines made by living things. It was first
recognized in natural selection, but it also accounts for the shaping and maintenance of the behavior of the individual and
the evolution of cultures. In al three of these fields, it replaces explanations based on the causal modes of classical mechanics.
The replacement is strongly resisted. Natural selection has now made its case, but similar delays in recognizing the role
of selection in the other fields could deprive us of valuable help in solving the problems which confront us.
It has been shown that uncontrollable shocks that produce learned helplessness also produce long-term opioid analgesia if th animal is re-exposed to shock immediately before the test. The present study was conducted in order to investigate if this effect can be observed 24h after the uncontrollable shock treatment without re-exposure to shock, and if it is opioid mediated. Long-term analgesia was found in the absence of re-exposure to shock, and was prevented by an i.p. injection of naloxone (10mg/kg) administered 10min before the test. The learned helplessness effect produced by the same shock treatment was prevented by the administration of 10 and 20mg/kg of naloxone 10min before the shuttlebox test, but not by a lower naloxone dose (5mg/kg). These findings suggest that the shock re-exposure requirement proposed in previous studies is not crucial in determining the long-term analgesia, and that both the long-term analgesia and the learned helplessness effect produced by this shock treatment were opioid mediated.
Three experiments investigated learned helplessness in rats manipulating response requirements, shock duration, and intervals between treatment and testing. In Experiment 1, rats previously exposed to uncontrollable or no shocks were tested under one of four different contingencies of negative reinforcement: FR 1 or FR 2 escape contingency for running, and FR1 escape contingency for jumping (differing for the maximum shock duration of 10s or 30s). The results showed that the uncontrollable shocks produced a clear operant learning deficit (learned helplessness effect) only when the animals were tested under the jumping FR 1 escape contingency with 10-s max shock duration. Experiment 2 isolated of the effects of uncontrollability from shock exposure per se and showed that the escape deficit observed using the FR 1 escape jumping response (10-s shock duration) was produced by the uncontrollability of shock. Experiment 3 showed that using the FR 1 jumping escape contingency in the test, the learned helplessness effect was observed one, 14 or 28 days after treatment. These results suggest that running may not be an appropriate test for learned helplessness, and that many diverging results found in the literature might be accounted for by the confounding effects of respondent and operant contingencies present when running is required of rats.
Desamparo aprendido e imunização utilizando o jato de ar quente como estímulo aversivo em ratos
- M B Carvalho-Neto
- D V N Oliveira
- D C Ferreira
Carvalho-Neto, M. B., Oliveira, D. V. N., & Ferreira, D. C. (2021). Desamparo aprendido e imunização utilizando o jato de
ar quente como estímulo aversivo em ratos. Acta Comportamentalia, 29(3), 113-131
Efeitos da (im)previsibilidade de estímulos no desamparo aprendido: uma comparação entre machos e fêmeas
- M C Z Castelli
Castelli, M. C. Z. (2004). Efeitos da (im)previsibilidade de estímulos no desamparo aprendido: uma comparação entre
machos e fêmeas. [Tese de Doutorado, Universidade de São Paulo].
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