Evaluation of blocking and conditioned inhibition to a CS signaling a decrease in US intensity

Two experiments employing a conditioned emotional response procedure with rats evaluated the associative tendencies acquired by a target CS when a compound of that stimulus and another CS was reinforced by a low-intensity US whereas the latter CS alone was reinforced by a higher intensity US. Experiment 1 involved a blocking sequence in which the element and compound trials occurred in successive phases, followed by eventual testing of the responding to the target CS alone. Less evidence of excitatory conditioning was observed than in a comparison group which had the element and compound paired with the same low-intensity US. Experiment 2 included contemporaneous differential reinforcement of the element and compound CSs and periodic summation tests in which the target CS was compounded with another independently trained CS. Clear evidence was obtained of the development of inhibitory tendencies by the target CS. The results are consistent with the predictions of the Rescorla-Wagner model and are discussed in relation to the several determining assumptions of the model.     

Intentional forgetting can increase, not decrease, residual influences of to-be-forgotten information.

Intentionally forgotten information remains in memory at essentially full strength, as measured by recognition and priming, but access to that information is impaired, as measured by recall. Given that pattern, it seemed plausible that intentionally forgotten information might have a greater impact on certain subsequent judgments than would intentionally remembered information. In 2 experiments, participants cued to forget nonfamous names were subsequently more likely to make false attributions of fame to those names than were participants instructed to remember them. These findings implicate retrieval inhibition as a potent factor in the interplay of recollection and priming in memory and judgment. They also point to possible unintended consequences of instructions to forget, suppress, or disregard in legal or social settings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trends in odor intensity for human and electronic noses: relative roles of odorant vapor pressure vs. molecularly specific odorant binding

Response data were collected for a carbon black-polymer composite electronic nose array during exposure to homologous series of alkanes and alcohols. The mean response intensity of the electronic nose detectors and the response intensity of the most strongly driven set of electronic nose detectors were essentially constant for members of a chemically homologous odorant series when the concentration of each odorant in the gas phase was maintained at a constant fraction of the odorant's vapor pressure. A similar trend is observed in human odor detection threshold values for these same homologous series of odorants. Because the thermodynamic activity of an odorant at equilibrium in a sorbent phase is equal to the partial pressure of the odorant in the gas phase divided by the vapor pressure of the odorant and because the activity coefficients are similar within these homologous series of odorants for sorption of the vapors into specific polymer films, the data imply that the trends in detector response can be understood based on the thermodynamic tendency to establish a relatively constant concentration of sorbed odorant into each of the polymeric films of the electronic nose at a constant fraction of the odorant's vapor pressure. Similarly, the data are consistent with the hypothesis that the odor detection thresholds observed in human psychophysical experiments for the odorants studied herein are driven predominantly by the similarity in odorant concentrations sorbed into the olfactory epithelium at a constant fraction of the odorant's vapor pressure.     

Naloxone blocks reinforcement but not motivation in an operant runway model of heroin-seeking behavior.

Examined the effects of opiate receptor antagonism on both the motivation to seek heroin and the reinforcing consequences of heroin administration. Male rats were trained to discriminate between olfactory cues predicting either the delivery of intravenous heroin reinforcement (S+) or saline (S-). Subjects were then tested in the presence of the opiate receptor antagonist, naloxone (0.5, 1.0, or 3.0 mg/kg intraperitoneally) in a straight-arm runway. Naloxone had no effect on either S+ or S- trials. However, 24 hr later on the first posttreatment trial, Ss that had received heroin in the presence of naloxone (on the previous trial) now traversed the alley more slowly when presented with the S+. These data suggest that although the motivation to seek heroin was not disrupted by naloxone, the reinforcing consequences of heroin administration were. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

LSD produces place preference and flavor avoidance but does not produce flavor aversion in rats.

The hedonic properties of lysergic acid diethylamide (LSD) were assessed using the place conditioning, taste reactivity, and taste avoidance tests. LSD produced a conditioned place preference, but only at the highest dose tested (0.2 mg/kg). A single preexposure to the conditioning chamber (latent inhibition) prevented the establishment of a place preference. When paired with sucrose, doses of 0.05 to 0.2 mg/kg of LSD produced taste avoidance, but no dose of LSD produced an aversion to the taste as assessed by the taste reactivity test. These results suggest that LSD, like other rewarding drugs, produces taste avoidance by a mechanism other than that produced by emetic drugs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tegmental pedunculopontine lesions in rats decrease saccharin's rewarding effects but not its memory-improving effect.

The tegmental pedunculopontine nucleus (TPP) of the brainstem has been identified as a critical substrate for both opiate and food reward in nondeprived rats. In this study of rats, TPP lesions blocked saccharin-conditioned place preferences, in both the presence and the absence of water deprivation. TPP lesions also attenuated the unconditioned intake of saccharin and water over several hours after recovery from food and water deprivation. TPP lesions did not block saccharin preferences over water in short-duration tests. The researchers propose that the absence of a lesion effect may reflect previously conditioned discriminations. TPP lesions had no effect on the ability of posttrial presentations of a 3.2% saccharin solution to improve LiCl-conditioned taste aversions. TPP lesions dissociate 2 behavioral processes elicited by saccharin: one mediates unconditioned-reward-conditioned-reinforcing effects, and another mediates the memory-improving effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dorsal hippocampal lesions impair blocking but not latent inhibition of taste aversion learning in rats.

The aim of the present experiments was to study the effect of nonselective electrolytic lesions of the rat dorsal hippocampus on 2 learning phenomena: the L. J. Kamin (1969) blocking effect and latent inhibition of taste aversion learning. Bilateral dorsal hippocampal lesions selectively impaired blocking induced by 1 saccharin-lithium chloride pairing previous to 1 serial compound (saccharin–cider vinegar)–lithium pairing, but lesions had no effect on latent inhibition of a saline aversion, induced by 6 saline preexposures, in the same group of animals. Moreover, dorsal hippocampal lesions did not affect latent inhibition of saccharin-conditioned aversion induced by 1 or 6 preexposures. It is argued that blocking and latent inhibition of taste aversion learning do not share a common neural mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitation of extinction by an increase or a decrease in trial duration.

Five experiments examined the effects of altering the duration of a conditioned stimulus (CS) for extinction. For the first 3 experiments, rats received conditioning with a 10-s CS before different groups received extinction with a CS that was either the same duration or longer than that used for conditioning. For the remaining 2 experiments, conditioning was conducted with a 60-s CS before different groups received extinction with a CS of either the same duration or a shorter duration than that used for conditioning. In all experiments, extinction progressed more readily when the CS duration was different for the 2 stages than when it was constant. The results are discussed in terms of rate expectancy theory and associative learning theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of secondary reinforcement effects in a comparison of partial reinforcement and partial delay of reinforcement.

Studied the effects of partial reinforcement and partial delay on extinction performance. 72 naive female albino Sprague-Dawley rats served as Ss. Secondary reinforcement effects were controlled by using the same delay-of-magazine interval on nonreinforcement trials with partial reinforcement (delay of empty magazine) as occurred on delayed trials with partial delay (delay of magazine containing sucrose). 4 delay intervals (0, 15, 30, and 45 sec) were factorially combined with the schedule variable. Resistance to extinction was an increasing function for the length of the delay interval and was greater for partial reinforcement than for partial delay. No interaction was observed to occur between the length of the delay interval and type of reinforcement schedule. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interleukin-12 p40 mRNA expression in bovine leukemia virus-infected animals: increase in alymphocytosis but decrease in persistent lymphocytosis

Interleukin-12 (IL-12), a key cytokine in immune regulation, has an important role in activating the cell-mediated immune response in infectious diseases. Recently, a dichotomy between IL-12 and IL-10 regarding progression of a variety diseases has emerged. IL-12 activates type 1 cytokine production and has an antagonistic effect on type 2 cytokines. Here, by using quantitative competitive PCR, we show that peripheral blood mononuclear cells from bovine leukemia virus-infected animals in the alymphocytotic stage of disease express an increased amount of IL-12 p40 mRNA. In contrast, IL-12 p40 mRNA expression by cells from animals with late-stage disease, termed persistent lymphocytosis, was significantly decreased compared to that by normal and alymphocytotic animals. Interestingly, IL-12 p40 mRNA was also detected in tumor-bearing animals. IL-12 p40 expression occurred only in monocytes/macrophages, not B or T lymphocytes. The present study combined with previous findings suggest that IL-12 in bovine leukemia virus-infected animals may regulate production of other cytokines such as gamma interferon and IL-10 and the progression of bovine leukosis in animals that develop more advanced disease such as a persistent lymphocytosis of B cells or B-cell lymphosarcoma.     

Early-life maternal separation and social isolation produce an increase in impulsive action but not impulsive choice.

Early life environment, events, and context, such as mother–offspring relationship, can have profound effects on future behavior and physiology. We investigated the effects of long-term maternal and social separation, through artificial rearing, on adult impulsivity. Rats were maternally reared (MR) or artificially reared (AR) and half of the AR rats were provided with replacement somatosensory stimulation intended to simulate maternal licking. There are at least 2 forms of impulsivity and we compared rats on 1 test of impulsive action (differential reinforcement of low rates of responding—DRL-20s) and 2 tests of impulsive choice (delay discounting and fixed consecutive number schedule—FCN). We found that AR rats are more action impulsive; however, this effect can be reduced by maternal licking-like stimulation. In contrast, AR rats did not display an increase in impulsive choice. Overall, these experiments show that early life maternal and social separation have different effects on the 2 forms of impulsivity. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Sparing of patterned alternation but not partial reinforcement effect after infant and adult hippocampal lesions in the rat.

Assessed the effect of hippocampal lesions in patterned (single) alternation (PSA) and the partial reinforcement extinction effect (PREE), the 2 reward-schedule effects that appear earliest in ontogeny. 147 Sprague-Dawley rats received hippocampal or sham lesions or served as unoperated controls. Three groups were tested for each effect: lesion as infant/test as infant; lesion as infant/test as adult; and lesion as adult/test as adult. Hippocampal lesions had no effect on PSA in any of the 3 conditions except for a suggestion that the effect was mildly attenuated in Ss given lesions as infants and tested as adults—Ss were able to discriminate rewarded from nonrewarded trials and to inhibit responding on nonrewarded trials. On the other hand, the PREE was eliminated under all conditions of testing, in each case because of an increase in persistence following continuously reinforced acquisition. Results are discussed in terms of the functional maturation of the hippocampus and a possible dissociation of mechanisms that mediate response suppression in PSA and in the PREE in infant rats. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estradiol or diarylpropionitrile decrease anxiety-like behavior of wildtype, but not estrogen receptor beta knockout, mice.

Clinical and basic studies demonstrate that estrogen (E?)-based therapies influence anxiety and mood, but the receptor targets (e.g., α or β isoform of the estrogen receptor, ER) for these effects requires further investigation. To address the specificity of E?'s anxiolytic-like effects through ERβ, anxiety, motor, and nociceptive behavior of ovariectomized, wildtype (WT), and ERβ knockout (βERKO) mice was examined. Mice were administered oil vehicle or ER agonists, 17β-E? (E?; 0.1 mg/kg; similar affinity for ERα and ERβ), and a selective ER modulator, diarylpropionitrile (DPN; 0.1 mg/kg; greater affinity for ERβ than ERα). Performance of mice in anxiety (open field, elevated plus maze, elevated zero maze, social interaction), motor activity (activity monitor) and nociception (tailflick, pawlick) measures was compared. Results supported our hypothesis that ERβ is important in modulation of anxiety-like behavior by E? in some tasks. Administration of E? or DPN to WT, but not βERKO, mice increased open field central entries, plus maze open arm time, zero maze open quadrant time, and social interaction. This pattern was neither seen in motor activity nor pain threshold measures. Thus, actions of ERβ may be important for modulating anxiety-like behavior of mice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebrospinal fluid C3a increases with age, but does not increase further in Alzheimer's disease

Complement activation is present in the brain in Alzheimer's disease (AD), and C1q concentrations are decreased in AD cerebrospinal fluid (CSF). To determine whether concentrations of other complement proteins are also altered in AD CSF, we measured concentrations of C3a and SC5b-9 in CSF from patients with probable AD (n = 19), normal aged controls (n = 11), and normal younger controls (n = 15). C3a concentrations were similar between AD and aged controls, but threefold higher than in younger controls (p < 0.05 vs. both groups). A similar pattern was found with SC5b-9, though the increase was only twofold and statistically significant only for AD vs. younger controls. These results suggest that an increased generation of complement proteins in localized areas of the AD brain does not result in elevated concentrations of these proteins in CSF, compared with age-matched controls. Increased C3a (and, to a lesser extent, SC5b-9) in aged controls may be due to increased complement activation, increased central nervous system production, and/or blood-brain barrier leakage of these proteins.     

Sparing of patterned alternation but not partial reinforcement extinction effect after prenatal chronic exposure to ethanol in infant rats.

The effects of in utero administration of ethanol on single patterned alternation (PA) and the partial reinforcement extinction effect (PREE) were studied in 15-day-old rat pups. This fetal-alcohol treatment had no effect on PA but eliminated the PREE by reducing persistence in extinction after partial reinforcement (PRF) training to its level after continuous reinforcement (CRF) training, which was not affected by the treatment. The results are discussed in terms of prenatal damage to the hippocampus and in relation to an earlier experiment (Lobaugh, Bootin, & Amsel, 1985), which found no effect of infant hippocampal lesions on PA but an elimination of the PREE, which, unlike the fetal-alcohol case, resulted from PRF-like persistence in extinction following CRF training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preference for delayed reinforcement: An experimental study of a cultural observation.

Ss included 53 male and female children between the ages of 7 and 9 in a rural Trinidad school. 35 were Negro and 18 were East Indian (29 males, 24 females). The "findings appear to have implications… for further research on relationships between personality variables." 15 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disruption of contextual freezing, but not contextual blocking of fear-potentiated startle, after lesions of the dorsal hippocampus.

[Correction Notice: An erratum for this article was reported in Vol 114(2) of Behavioral Neuroscience (see record 2007-17251-001). The captions for Figure 4 (p. 70) and Figure 5 (p. 72) were printed incorrectly. The caption used for Figure 4 should appear under Figure 5, and the caption used for Figure 5 should appear under Figure 4.] The role of the dorsal hippocampus in contextual fear conditioning was investigated with a contextual blocking paradigm. In Experiment 1, rats were given pairings of a light conditioned stimulus (CS) and footshock after preexposure either to footshock or to the context alone. The group preexposed to footshock showed poorer fear conditioning to the light CS, as measured by the fear-potentiated startle reflex. In Experiment 2, a group preexposed to footshock in the same context showed poorer fear conditioning to the light CS than did a group preexposed to footshock in a different context, indicating contextual blocking of fear-potentiated startle. In Experiment 3, lesions of the dorsal hippocampus had no effect on contextual blocking, even though contextual freezing was disrupted. The sparing of contextual blocking indicated that contextual memory was intact following hippocampal lesions, despite the disruption of contextual freezing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactivity and aggression in the rat: Induction by !a-adrenergic blocking agents injected ventral to anterior septum but not into lateral septum.

Intracranial injections were made bilaterally through permanently implanted cannulas ending in the lateral septum or in the region ventral to the anterior septum of 78 male hooded rats. Ss were first screened with injections of a local anesthetic, lidocaine, which blocks both synaptic and axonal conduction. Those Ss that showed an increase in reactivity and aggression were then injected with a synaptic transmitter blocking agent. Results show that transmitter blocking agents reproduced the effect of the local anesthetic only in the region ventral to the anterior septum and that α-adrenergic (phentolamine, tolazoline), but not β-adrenergic (propranolol, hydralazine), cholinergic (atropine, hyocine), or dopaminergic (haloperidol) blocking agents were effective. Results suggest that synapses in the forebrain system controlling reactivity and aggression are α-adrenergic and are located in the region ventral to the anterior septum just lateral to the diagonal band of Broca. The septum itself may be involved only to the extent that it is transversed by fibers of passage. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions of the pedunculopontine tegmental nucleus increase sucrose consumption but do not affect discrimination or contrast effects.

Pedunculopontine tegmental nucleus (PPTg) lesions block place preferences to drugs or food only when animals are nondeprived. PPTg lesions also disrupt operant responding, but lesioned rats cannot discriminate active from inactive levers. It is not clear, therefore, whether PPTg lesions block reward or disrupt the ability to differentiate changes in reward magnitude. These hypotheses were tested by measuring sucrose consumption, choice, and contrast effects after PPTg lesions. Both sham and lesioned rats consumed greater amounts of a sucrose solution as the concentration and level of deprivation were increased. Given a choice between 2 solutions, all rats consumed more of the higher concentration. Both groups exhibited contrast effects when the concentration was shifted from 32% to 4% within a session. Somewhat surprisingly, lesions increased sucrose intake when rats were food-restricted. These results suggest that PPTg lesions do not disrupt primary motivation or the ability to evaluate and respond to changes in reward strength. (PsycINFO Database Record (c) 2010 APA, all rights reserved)