Attributions modulate immunization against learned helplessness in humans.

Conducted 3 experiments to determine the effect of global and internal attributions on immunization against learned helplessness. Exp 1 replicated the helplessness effect and its immunization. This immunization effect was weakened in Ss with global internal attributions about negative events and strengthened in Ss with specific and external attributions. In Exp 2, previous attributional style did not produce any effect on either immunization or helplessness. However, instructions to induce global internal attributions produced an enhanced helplessness effect. In Exp 3, global internal attributions induced by instructions during uncontrollability, but not during controllability, produced significant differences in the immunization effect. Immunization against helplessness was a function of a previous controllable experience, and attributions represented a vulnerability factor that modulated the actual influence of previous experiences on new tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The opioid/nonopioid nature of stress-induced analgesia and learned helplessness.

Investigated whether the same factors that activate the processes that produce escape interference might also activate processes leading to opioid stress-induced analgesia (SIA). Exposure to a variety of stressors produces a subsequent analgesic reaction that is sometimes opioid in nature (reversed by opiate antagonists and cross-tolerant with morphine) and sometimes nonopioid. In Exp I, 40 male albino rats were subjected to 20 min of intermittent footshock, 3 min of continuous footshock, tailshock on a VI schedule, or confinement only. Ss were given escape/avoidance training 24 hrs later. In Exp II, 36 Ss received SIA with a tail-flick apparatus. In Exp III, 40 Ss received inescapable tailshocks or confinement only. In Exp IV, 24 Ss received 2 sessions of footshock before tail-flick was assessed. Both of the opioids SIA procedures produced a learned helplessness effect as assessed by shuttlebox escape acquisition and an analgesia that was reinstatable 24 hrs later. The nonopioid procedures produced neither a learned helplessness effect nor a reinstatable analgesia. These data implicate the learning of uncontrollability in the activation of opioid systems. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned helplessness and immunization: Sensitivity to response–reinforcer independence in immunized rats.

Exps I and II, with 62 male Holtzman rats, examined the learned helplessness and immunization effects using a test in which appetitive responding was extinguished by delivering noncontingent reinforcers. Contrary to learned helplessness theory, "immunized" Ss showed performance virtually identical to that of Ss exposed only to inescapable shock and different from that of nonshock controls. Exp II suggested that the helplessness effect and the lack of immunization were not due to direct response suppression resulting from shock. In Exp III, in which the immunization effect was assessed in 28 Ss by measuring the acquisition of a response to obtain food when there was a positive response–reinforcer contingency, immunization was observed. Results cannot be explained on the basis of proactive interference and instead suggest that Ss exposed to the immunization procedure acquired an expectancy of response–reinforcer independence during inescapable shock. Thus, immunization effects may reflect the differential expression of expectancies rather than their differential acquisition as learned helplessness theory postulates. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DNA vaccination affords significant protection against feline immunodeficiency virus infection without inducing detectable antiviral antibodies

To test the potential of a multigene DNA vaccine against lentivirus infection, we generated a defective mutant provirus of feline immunodeficiency virus (FIV) with an in-frame deletion in pol (FIVDeltaRT). In a first experiment, FIVDeltaRT DNA was administered intramuscularly to 10 animals, half of which also received feline gamma interferon (IFN-gamma) DNA. The DNA was administered in four 100-microg doses at 0, 10, and 23 weeks. Immunization with FIVDeltaRT elicited cytotoxic T-cell (CTL) responses to FIV Gag and Env in the absence of a serological response. After challenge with homologous virus at week 26, all 10 of the control animals became seropositive and viremic but 4 of the 10 vaccinates remained seronegative and virus free. Furthermore, quantitative virus isolation and quantitative PCR analysis of viral DNA in peripheral blood mononuclear cells revealed significantly lower virus loads in the FIVDeltaRT vaccinates than in the controls. Immunization with FIVDeltaRT in conjunction with IFN-gamma gave the highest proportion of protected cats, with only two of five vaccinates showing evidence of infection following challenge. In a second experiment involving two groups (FIVDeltaRT plus IFN-gamma and IFN-gamma alone), the immunization schedule was reduced to 0, 4, and 8 weeks. Once again, CTL responses were seen prior to challenge in the absence of detectable antibodies. Two of five cats receiving the proviral DNA vaccine were protected against infection, with an overall reduction in virus load compared to the five infected controls. These findings demonstrate that DNA vaccination can elicit protection against lentivirus infection in the absence of a serological response and suggest the need to reconsider efficacy criteria for lentivirus vaccines.     

Identification and initial characterization of mSLK, a murine member of the STE20 family of kinases

Among 2099 uninfected subjects in phase I and II trials of candidate AIDS vaccines, 23 were diagnosed with intercurrent human immunodeficiency virus type 1 (HIV-1) infection. High-risk sexual exposures accounted for 17 infections, and intravenous drug use accounted for 6. Four subjects received placebo, 13 received a complete immunization schedule (> or = 3 injections), and 6 were partially immunized (< or = 2 injections). There was no significant difference between vaccine recipients and control groups in incidence of HIV-1 infection, virus load, CD4 lymphocyte count, or V3 loop amino acid sequence. In summary, 19 vaccinated subjects acquired HIV-1 infection during phase I and II trials, indicating that immunization with the products described is < 100% effective in preventing or rapidly clearing infection. Laboratory analysis suggested that vaccine-induced immune responses did not significantly affect the genotypic or phenotypic characteristics of transmitted virus or the early clinical course of HIV-1 infection.     

The efficacy of recombinant vaccines against hepatitis B and the results of their use in a schedule for pediatric prophylactic inoculations

The results of field clinical trials of Russian and American yeast vaccines against hepatitis B are presented. The study revealed that both vaccines were faintly reactogenic, safe and exhibited high immunological activity. After the full course of immunization following the schedule 0-1-2 months 92.5% and 97.5% of patients receiving, respectively. Russian vaccine "Combiotech" and American vaccine "H-B-Vax II" were found to have specific antibodies. The maximum effect was registered when the vaccines were introduced according to the schedule 0-1-6 months. Seroconversions were observed in 97.5% and 100% of the vaccinees receiving the Russian and American vaccines respectively, in the latter case the highest antibody level being observed. The use of the vaccines within the prophylactic immunization schedule showed that antibodies to hepatitis B appeared in immunized children in 93-100% of cases. Seroconversion indices and the levels of antibodies to diphtheria, tetanus, poliomyelitis and measles were statistically significant and were the same in children receiving only the vaccines according to the immunization schedule and in children immunized, in addition to these vaccines, against hepatitis B.     

Uncontrollable shock proactively increases sensitivity to response-reinforcer independence in rats.

Learned helplessness theory predicts that animals exposed to inescapable shock acquire an expectancy of response-reinforcer independence, which proactively interferes with learning of response-reinforcer dependence. The theory also predicts that this expectancy can increase sensitivity to subsequent instances of response-reinforcer independence. Two experiments, with 42 male Holtzman rats, tested the latter prediction in a paradigm that minimized the confounding effects of shock-induced activity deficits. In Exp I, Ss were trained to respond for food, then given either escapable, inescapable, or no shock. Subsequently, they received 2 sessions of response-contingent food followed by sessions of noncontingent food deliveries. During this phase, inescapably shocked Ss decreased responding faster than did controls. Exp II replicated this finding with a different schedule of food delivery and a procedure that more directly minimized the possibility that the outcome was due to either direct or indirect shock-induced activity changes. Results support the prediction that uncontrollable aversive events can increase an animal's sensitivity to noncontingent response-reinforcer relationships. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paradoxical enhancement of learned fear.

Conducted 2 experiments to demonstrate that presentation of the CS alone, after conditioning, can enhance learned fear. In Exp. I, groups of 12 Holtzman albino rats received 0-, 1/2-, 5-, 15-, or 50-min postconditioning exposure to the apparatus (the CS) in which they had previously been shocked. Results suggest that the 5-min exposure group was more fearful than the nonexposed controls. In Exp. II, 32 male Holtzman albino weanling rats were conditioned to fear 1 compartment in a shuttle box, followed 2 wk. later by interpolated exposures to the fear cues alone for 0, 30, 60, or 300 sec. 30- and 60-sec exposures produced significantly more spatial avoidance than 0- and 300-sec exposures. (34 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitation of instrumental behavior by a Pavlovian appetitive conditioned stimulus.

In Exp I, 16 New Zealand white rabbits were trained to perform an instrumental head-raising response for sucrose reward. A jaw-movement CR was established to a 2-sec CS by pairing it with sucrose; a control stimulus was unpaired with sucrose. Instrumental responding maintained by a VI 40-sec schedule was enhanced during 10-sec presentations of the paired, but not the unpaired, CS. Responding on a VR 15 schedule was unaffected except on trials on which the pre-CS baseline response rate was low; in such cases the paired CS caused a long-lasting acceleration of responding. Noncontingent presentation of the sucrose reinforcer itself briefly suppressed responding but had no long-term effect. In Exp II (6 Ss), a CS that had been conditioned at a 10-sec duration produced the same pattern of effects as in Exp I, indicating that facilitation resulted from CS presentation rather than from the frustrative effects of nonreinforcement of the CS. In Exp III (16 Ss), an inhibitory CS blocked facilitation by the excitatory CS but did not itself affect instrumental responding. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats prefer signaled over unsignaled shock-free periods.

Three experiments with 48 female rats investigated Ss' preference for a schedule of shock containing signaled shock-free periods (SSF schedule) or the same shock schedule without signals (unsignaled schedule). Exp I was a replication of the shuttle-box experiment reported by M. S. Fanselow (see record 1981-00807-001), in which rats preferred unsignaled shock over the SSF schedule. Contrary to Fanselow's results, Ss in Exp I failed to develop a preference. In Exp II, forced-exposure training was added, testing was extended from 2 165-min sessions to 8, and a reversal phase was added. Results show that 3 of 4 Ss preferred the SSF schedule, and 2 of these continued to prefer it after reversal. In Exp III, forced-exposure training was eliminated, but signals were lengthened from 30 to 60 sec, and the test was extended to 12 sessions. Results show that Ss choosing between the unsignaled and SSF schedules chose the SSF schedule, whereas a random control group chose the unsignaled schedule. Findings indicate that choice between active schedules is determined by the relative aversiveness of all stimuli presented and not, as implied by contextual fear analysis, by that of contextual stimuli alone. (25 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Confounding of controllability in the triadic design for demonstrating learned helplessness.

The triadic design for producing learned helplessness was analyzed in 2 experiments and found to be logically deficient for defining the theoretical construct of controllability. Two experiments with 120 university students were performed. In Exp I, the 1st group was preexposed to a noxious tone that could be terminated by a button-press. The 2nd and 3rd groups, which were yoked to the 1st, could not escape the tone. A 4th group received no tone preexposures. A 5th group, yoked to the 1st, was instructed to press the button when the tone terminated. Groups 4 and 5, which had no controllability over tone-offset but which did have a 2nd event immediately following the tone, both showed significantly better performance on a subsequent tone-escape task than Group I. Exp II replicated these findings. Data indicate that controllability may be a sufficient but not a necessary condition in the triadic design for preventing subsequent learned helplessness. It follows logically that uncontrollability is not the appropriate designation of the process(es) involved in producing such effects. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned helplessness and learned resourcefulness: Effects of noncontingent success and failure on individuals differing in self-control skills.

In Exp I, 72 undergraduates were assessed using the Self-Control Schedule and received noncontingent success-, failure-, or no-feedback on a task that ostensibly assessed therapeutic abilities. Ss were subsequently tested on insolvable puzzles. In Exp II, 72 undergraduates followed the same procedure as in Exp I but were subsequently tested on solvable anagrams. Results show that the performance of Ss with low resourcefulness (LR) in self-control skills on the insolvable puzzles was debilitated by the helplessness induction, while Ss with high resourcefulness (HR) and LR Ss showed equal helplessness-induced deficits on the anagrams. As predicted from the self-control model, HR Ss more frequently checked statements indicating positive self-evaluations and task-oriented thoughts and less frequently checked negative self-evaluations than did LR Ss during exposure to uncontrollability in both experiments. It is concluded that the self-control model best accounts for Ss' self-reactions during exposure to uncontrollability or failure, while the learned helplessness model accounts for the generalization of helplessness from uncontrollable situations to controllable ones. The list of self-referent statements used in the experiments is appended. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some aspects of preference between immediate and delayed periods of reinforcement.

Two studies, with 6 homing pigeons, investigated an analog of the usual self-control paradigm by investigating choice between differently delayed reinforcer rates. Ss were trained on a concurrent-chain schedule in which the initial links (ILs) were equal VI schedules. The immediate terminal link (TL) consisted of an immediate 30-sec access to a VI schedule of food reinforcers, followed by a 30-sec blackout. The delayed TL consisted of an immediate 30-sec blackout followed by a 30-sec access to a VI food reinforcer schedule. Exp I comprised 3 parts, in each of which the TL VI schedules were varied. In Exp Ia, the IL responses that produced entries into both TLs were additionally reinforced with food; in Exp Ib, only the IL responses that produced entries into the delayed TL were additionally reinforced with food; and in Exp Ic, none of the IL responses that produced TL entries were additionally reinforced. When no TL entry responses were reinforced, IL response allocation was highly sensitive to variations in the TL schedules. Reinforcing entries into the delayed TLs (Exp Ib) decreased this sensitivity, and reinforcing entries into both TLs (Exp Ia) completely eliminated differential control by the TL reinforcer rates. Exp II varied the frequency of reinforcers for entries into the delayed TL and showed that even infrequent reinforcers strongly affected IL behavior allocation. Results are consistent with theories in which reinforcer value is a function of the summation of individual delays to reinforcing events. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attenuation of punishing effects of morphine and amphetamine by chronic prior treatment.

In a previous study L. Parker et al (see record 1973-20548-001) found that the gustatory aversion normally produced by morphine did not occur when rats were first made dependent on the drug. Their explanation of this phenomenon was that dependent, withdrawn animals are in an "unnatural need state" such that a taste stimulus paired with morphine will become preferred by pairing with a beneficial need-replenishing event. This explanation was examined in the present 2 experiments with a total of 180 male Wistar rats. In Exp I the Parker et al results were supported in a conceptually similar experiment. In Exp II it was shown that analogous results could be produced with amphetamine, a drug upon which physicial dependence has not been unequivocally demonstrated and for which the regulation of self-administration does not follow the morphine pattern. Since the evidence for a "need" artificially induced by amphetamine withdrawal was not strong, the hypothesis that these data reflect preference for a substance associated with need reduction may be questioned. Of the various explanations for the phenomenon, only one involving the concept of drug tolerance has no arguments against it. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The hippocampus, collateral behavior, and timing.

Male Sprague-Dawley rats with hippocampal (HC) lesions, cortical control lesions, or sham operations were trained to leverpress on a DRL schedule requiring 12 sec between responses. In 4 experiments, factors affecting performance efficiency in this paradigm were manipulated. Providing extra opportunities for collateral mediating behavior (Exp I) aided all groups nondifferentially. Adding a limited hold (Exp II) or administering chlordiazepoxide HCl (Exp III) reduced DRL efficiency in all groups nondifferentially. However, adding an auditory stimulus marking the halfway point in the DRL requirement (Exp IV) differentially aided the HC group. Implications for theories of HC function are discussed. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task specificity in nonspecific transfer and in extradimensional stimulus generalization in pigeons.

Determined whether discrimination training per se is sufficient to produce positive nonspecific transfer and whether it sharpens extradimensional stimulus-generalization gradients, using domestic pigeons. In Exp I, 8 groups of Ss received true-discrimination (TD) or pseudodiscrimination training between 2 line orientations in either (a) a successive-conditional (SC) discrimination prior to transfer to a true SC or (b) a go/no go (GN) discrimination between 2 colors. Discriminative performance in transfer was facilitated only when the original and transfer discriminations were of the same type. Exp II showed that positive nonspecific transfer was primarily mediated by the transfer of task-specific learning rather than by the transfer of attentiveness. In Exp III, 4 groups were trained as in Stage 1 of Exps I and II and given single-stimulus training with a chromatic stimulus, followed by a wavelength stimulus generalization test. Only TD-GN discrimination training produced sharp gradients, an effect leading to the conclusion that GN discrimination training and stimulus generalization are closely related by task requirements rather than by attention. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Water drinking induced in sheep by angiotensin: A physiological or pharmacological effect?

The effect of val5-angiotensin II amide on water drinking in sheep was studied against a background of comprehensive data on arterial blood and cerebrospinal fluid angiotensin II levels in sheep under a variety of physiological conditions. 10 sheep of Corriedale or Merino breeds were used in Exp I and 4 in Exp II; 5 ewes were used in Exp III. Physiological range of blood angiotensin II concentration is 1-100 ng/100 ml. Intravenous infusion of angiotensin II within the physiological range did not increase water drinking. Intracarotid infusion of angiotensin II, or injection into 3rd ventricle or hypothalamus, consistently caused immediate drinking of large amounts of water. Dosages necessary for effect were in the supraphysiological range. Quantitative examination of data in sheep and other species suggests that a physiological role for angiotensin II in thirst is not proved. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response–reinforcer associations after caudate-putamen lesions in the rat: Spatial discrimination and overshadowing–potentiation effects in instrumental learning.

Exp I, with 12 male hooded rats, demonstrated that Ss with caudate-putamen lesions exhibited an impairment in the acquisition and reversal of a spatial maze task when compared with unoperated control Ss. Exp II, with 24 Ss, investigated leverpress responding supported by a VI schedule in 3 groups of Ss: a group with caudate-putamen lesions, a group with lesions of the posterior cortex, and an unoperated control group. The presentation of a 0.5-sec, response-contingent light correlated with reinforcement generated an elevated response rate in the 2 operated groups but tended to suppress responding in the control group, perhaps by overshadowing the response–reinforcer relation. Only the group with cortical lesions maintained the elevated rate when the light was uncorrelated with food delivery. Exp III confirmed for these same Ss that caudate-putamen lesions produced a spatial learning deficit. No deficit was observed in the posterior cortex group. It is suggested that caudate-putamen lesions disrupt the mechanism underlying the response–reinforcer association on which spatial maze learning and free operant responding in part depend. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Probability learning on incidentally observed dimensions: A response bias effect.

Performed 2 experiments with 140 university students which demonstrate the occurrence of response bias effects as a function of previous probability learning and which are independent of stimulus dimensions. In Exp I, Ss first received training predicting the alternatives on a brightness dimension of metric patterns on a 70-30 probability distribution with the incidental dimensions of symmetry and concentration varying independently either on 70-30 or 50-50 distributions. After 200 trials, Ss were shifted to an incidental dimension; they predicted dimension alternatives on the incidental dimensions at a rate higher than appropriate controls Ss with no prior training. Exp II demonstrated that the response bias effect was dependent on the nature of the prior probability training. Ss first predicted on a 70-30 distribution of shape and were shifted to either a 70-30 or 50-50 distribution of nonsense syllables. Comparisons with nontraining control groups showed that Ss with prior training predicted the nonsense syllable alternatives at a higher rate. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of overtraining on reversal and extradimensional shifts in schizophrenics.

In Exp. I, 50 schizophrenic Ss were trained under 1 of 3 discrimination learning conditions: reversal (R) shift, extradimensional (ED) shift, or control. 1/2 of the Ss in each shift condition received overtraining on the preshift discrimination. Performances of nonovertrained Ss on the R and ED shifts were very similar to performances of schizophrenic Ss tested by J. D. Nolan (see 42:11). Newman-Keuls analyses indicate that overtraining facilitated the R shift relative to the ED shift. The result was a significant overall effect due to shift type. In Exp. II, a replication of Exp. I, 60 undergraduates learned R shifts faster than ED shifts, but overtraining had no discernible effect. Results were compared with those reported by Nolan and were discussed in terms of a 2-stage attention model of discrimination learning. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)