Mechanisms of resurgence II: Response-contingent reinforcers can reinstate a second extinguished behavior

Three experiments with rat subjects examined resurgence of an extinguished instrumental response using the procedure introduced by Epstein (1983) with pigeons. There were three phases: (1) initial acquisition of pressing on a lever (L1) for pellet reward, (2) extinction of L1, and (3) a test session in which a second lever (L2) was inserted, briefly reinforced, and then extinguished. Experiment 1 confirmed that if pressing L2 delivered 20 pellets followed by extinction, rats would resume L1 responding in the final test. Experiment 2 compared the effects of response-contingent and non-contingent rewards delivered upon insertion of L2. Although insertion of L2 alone did not increase L1 responding, response-contingent and non-contingent rewards led to comparable increases in L1 responding. Experiment 3 found that the delivery of non-contingent pellets during extinction of L1, which would be expected to reduce the ability of pellets to set the occasion for the L1 response, also reduced the effects of both response-contingent and non-contingent rewards during the final test. The results indicate that in this method, the resurgence treatment leads to an increase in L1 pressing due to simple presentation of the pellet; delivering the reinforcer after extinction of L1 reinstates L1 responding by setting the occasion for the L1 response.     

A functional approach for research on cognitive control: Analysing cognitive control tasks and their effects in terms of operant conditioning

Cognitive control is an important mental ability that is examined using a multitude of cognitive control tasks and effects. The present paper presents the first steps in the elaboration of a functional approach, which aims to uncover the communalities and differences between different cognitive control tasks and their effects. Based on the idea that responses in cognitive control tasks qualify as operant behaviour, we propose to reinterpret cognitive control tasks in terms of operant contingencies and cognitive control effects as instances of moderated stimulus control. We illustrate how our approach can be used to uncover communalities between topographically different cognitive control tasks and can lead to novel questions about the processes underlying cognitive control.     

Visual perceptual learning by operant conditioning training follows rules of contingency

Visual perceptual learning (VPL) can occur as a result of a repetitive stimulus-reward pairing in the absence of any task. This suggests that rules that guide Conditioning, such as stimulus-reward contingency (e.g., that stimulus predicts the likelihood of reward), may also guide the formation of VPL. To address this question, we trained subjects with an operant conditioning task in which there were contingencies between the response to one of three orientations and the presence of reward. Results showed that VPL only occurred for positive contingencies, but not for neutral or negative contingencies. These results suggest that the formation of VPL is influenced by similar rules that guide the process of Conditioning.     

Transfer of avoidance responding to a sensory preconditioned cue: Evidence for the role of S-S and R-S knowledge in avoidance learning

In avoidance learning studies, a warning signal (Sd) is directly paired with an aversive unconditioned stimulus (US) unless a particular response is performed. Research by Augustson and Dougher (1997) demonstrated that not only warning signals but also stimuli that are indirectly paired with the aversive event are capable of affecting the avoidance response. In the present study, we extended these results by incorporating a sensory preconditioning paradigm in an avoidance learning procedure. Sensory preconditioning training influenced the selection of avoidance responses in the presence of warning signals that were never paired directly with the aversive events. Moreover, results suggest that the selection of the avoidance responses was based on an integration of knowledge about the relation between the Sd and the US (S-S knowledge) and knowledge about the relation between the avoidance response and the US (R-S knowledge). As the expectancy-based theory of Lovibond (2006) is the only theory of avoidance that incorporates both knowledge structures, the results provide unique support for this theory.     

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.     

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.     

Stress associated changes in Pavlovian-instrumental transfer in humans

Predictive learning is known to influence instrumental responding for reward. Cues associated with an instrumental outcome can influence performance in two ways: (a) by selectively promoting actions associated with the outcome predicted by the cue (specific transfer), and (b) by increasing motivation and the vigour of instrumental responding (general transfer). To examine these two distinct processes in humans we developed a novel behavioural task in which participants were able to liberate junk-food snacks from a virtual vending machine. Additionally, the relationship between stress and cue-driven reward seeking was examined using participant scores on the Depression Anxiety and Stress Scale (DASS). Reward-paired cues were found to separately bias action selection and influence the rate of responding for rewards. Furthermore, the effects of reward-paired cues on the rate of responding for reward was influenced by increased stress and anxiety. Increased levels of stress and anxiety were associated particularly with changes in cue-driven response vigour; whereas high levels of stress and anxiety were associated with elevated responding above baseline in the presence of a cue associated with a non-rewarding outcome, participants with low levels of anxiety and stress showed appropriate suppression of responding during this cue. These differences in performance between high and low anxiety and stress participants provides initial evidence that, as has been demonstrated in rodents, stress affects the influence of cue-driven response vigour in humans.     

Outcome-specific transfer between predictive and instrumental learning is unaffected by extinction but reversed by counterconditioning in human participants

Three experiments were conducted to explore the effects of different interference treatments upon outcome-specific transfer from predictive learning to instrumental responding. A computer game was designed in which participants had to defend Andalusia from navy and air-force attacks. Participants learned the relationship between two instrumental responses (two keys in a standard keyboard) and two different outcomes (destruction of the ships or destruction of the planes). Then, they learned to predict which of two different cues predicted either outcome. Finally, participants were allowed to give either of the two instrumental responses in the presence of each cue. Outcome-specific transfer was shown as a preference for the response that shared the outcome with the current cue. Extinction of the cue before the transfer test had no effect upon transfer, regardless of the level of extinction (Experiments 1-3). However, pairing the cue with the alternative outcome (counterconditioning) reversed the outcome-based transfer effect (Experiment 3). The implications of these results for the contents of extinction in human predictive learning are discussed.     

Instrumental and vocal music effects on EEG and EKG in neonates of depressed and non-depressed mothers

Neonates (M age = 16 days) born to depressed and non-depressed mothers were randomly assigned to hear an audiotaped lullaby of instrumental music with vocals or without vocals. Neonatal EEG and EKG were recorded for 2 min (baseline) of silence and for 2 min of one or the other music presentation. Neonates of non-depressed mothers showed greater relative right frontal EEG asymmetry to both types of music, suggesting a withdrawal response. Neonates of depressed mothers on the other hand showed greater relative left frontal EEG asymmetry to the instrumental without vocal segment, suggesting an approach response, and greater relative right frontal EEG asymmetry to the instrumental with vocal segment, suggesting a withdrawal response. Heart rate decelerations occurred following the music onset for both groups of infants, however, compared to infants of non-depressed mothers, infants of depressed mothers showed a delayed heart rate deceleration, suggesting slower processing and/or delayed attention. These findings suggest that neonates of depressed and non-depressed mothers show different EKG and EEG responses to instrumental music with versus without vocals.     

Sex categorization of conspecific pictures in Japanese monkeys (Macaca fuscata)

We investigated whether monkeys discriminate the sex of individuals from their pictures. Whole-body pictures of adult and nonadult monkeys were used as stimuli. Two male Japanese monkeys were trained for a two-choice sex categorization task in which each of two choice pictures were assigned to male and female, respectively. Following the training, the monkeys were presented with novel monkey pictures, and whether they had acquired the categorization task was tested. The results suggested that while monkeys discriminate between the pictures of adult males and females, discrimination of nonadult pictures was difficult. Partial presentations of the pictures showed that conspicuous and sexually characteristic parts (i.e., underbellies including male scrotums or breasts including female nipples) played an important role in the sex categorization.     

Varenicline ameliorates ethanol-induced deficits in learning in C57BL/6 mice

Ethanol is a frequently abused drug that impairs cognitive processes such as learning. Varenicline, an α4β2 nicotinic receptor partial agonist and α7 nicotinic receptor full agonist prescribed for smoking cessation, has been shown to decrease ethanol consumption. The current study investigated whether varenicline could ameliorate ethanol-induced deficits in learning and whether varenicline alters blood alcohol concentration in C57BL/6 mice. Conditioning consisted of two auditory conditioned stimulus (CS; 30 s, 85 dB white noise)—foot shock unconditioned stimulus (US; 2 s, 0.57 mA) pairings. For all studies, saline or ethanol (1.0, 1.5, 2.0 g/kg i.p.) was administered 15 min before training, and saline or varenicline (0.05, 0.1, 0.2 mg/kg i.p.) was administered 60 min before either training or testing. For blood alcohol analysis, saline or varenicline (0.1 mg/kg) was administered 60 min before collection, and saline or ethanol (1.0, 1.5, 2.0 g/kg) was administered 15 min before collection. Varenicline dose-dependently ameliorated ethanol-induced conditioning deficits for all three doses of ethanol when administered before training but not when administered 24 h later, before testing. In addition, varenicline did not alter blood alcohol concentration. The smoking cessation aid varenicline may have therapeutic uses for treating ethanol-associated disruptions in cognitive processes.     

High impact running improves learning

Regular physical exercise improves cognitive functions and lowers the risk for age-related cognitive decline. Since little is known about the nature and the timing of the underlying mechanisms, we probed whether exercise also has immediate beneficial effects on cognition. Learning performance was assessed directly after high impact anaerobic sprints, low impact aerobic running, or a period of rest in 27 healthy subjects in a randomized cross-over design. Dependent variables comprised learning speed as well as immediate (1 week) and long-term (>8 months) overall success in acquiring a novel vocabulary. Peripheral levels of brain-derived neurotrophic factor (BDNF) and catecholamines (dopamine, epinephrine, norepinephrine) were assessed prior to and after the interventions as well as after learning. We found that vocabulary learning was 20 percent faster after intense physical exercise as compared to the other two conditions. This condition also elicited the strongest increases in BDNF and catecholamine levels. More sustained BDNF levels during learning after intense exercise were related to better short-term learning success, whereas absolute dopamine and epinephrine levels were related to better intermediate (dopamine) and long-term (epinephrine) retentions of the novel vocabulary. Thus, BDNF and two of the catecholamines seem to be mediators by which physical exercise improves learning.     

Interoceptive fear conditioning as a learning model of panic disorder: an experimental evaluation using 20% CO(2)-enriched air in a non-clinical sample

Despite the role afforded interoceptive fear conditioning in etiologic accounts of panic disorder, there are no good experimental demonstrations of such learning in humans. The aim of the present study was to evaluate the interoceptive conditioning account using 20% carbon dioxide (CO(2))-enriched air as an interoceptive conditioned stimulus (CS) (i.e., physiologically inert 5-s exposures) and unconditioned stimulus (US) (i.e., physiologically prepotent 15-s exposures). Healthy participants (N=42) were randomly assigned to one of three conditions: a CS-only, contingent CS-US pairings, or unpaired/non-contingent CS and US presentations. Electrodermal and self-report (e.g., distress, fear) served as indices of conditioned emotional responding. Results showed greater magnitude electrodermal and evaluative fear conditioning in the paired relative to the CS-only condition. The explicitly unpaired condition showed even greater electrodermal and evaluative responding during acquisition, and marked resistance to extinction. The latter results are consistent with the possibility that the unpaired procedure constituted a partial reinforcement procedure in which CO(2) onset was paired with more extended CO(2) exposure on 50% of the trials. Overall, the findings are consistent with contemporary learning theory accounts of panic.     

Lack of phenotype for LTP and fear conditioning learning in calpain 1 knock-out mice

We previously proposed the hypothesis that calpain activation played an important role in long-term potentiation (LTP) of synaptic transmission in hippocampus. Two forms of calpain are predominant in brain tissues, calpain 1 (mu-calpain), activated by micromolar calcium concentration and calpain 2 (m-calpain), activated by millimolar calcium concentration in vitro. In the present study, we tested the role of calpain 1 in LTP and in learning and memory using calpain 1 knock-out mice. Changes in learning and memory were assessed using both context and tone fear conditioning. No differences in freezing responses were observed between the knock-out and the wild-type animals during the acquisition phase of the training, eliminating the possibility that the knock-out animals could be differentially affected by the foot shock. Likewise, no differences in freezing responses elicited by either the context or the tone were observed during the retention phase. No differences in short-term potentiation (STP) or LTP were observed in hippocampal slices from the knock-out and matched wild-type mice. Several interpretations might explain these negative results. First, it is conceivable that calpain 2 plays a more dominant role in neurons, and that calpain 1 makes a minor contribution as opposed to its suspected predominant role in the hematopoietic system. Alternatively, it is conceivable that some as yet unknown compensatory mechanisms take effect, and that calpain 2 or another calpain isoform substitutes for the missing calpain 1.     

Associations in human instrumental conditioning

Four experiments were conducted to study the contents of human instrumental conditioning. Experiment 1 found positive transfer between a discriminative stimulus (S^D) and an instrumental response (R) that shared the outcome (O) with the response that was originally trained with the S^D, showing the formation of an S^D → O association. Experiment 2 found that post-acquisition devaluation of an outcome selectively reduced the response trained with that outcome, showing the formation of a R → O association. In Experiment 3, changing the outcome did not prevent participants from giving the response learned with each S^D, even though none of the responses was appropriate for the new outcome, showing evidence of the formation of S^D → R associations in instrumental learning. The three binary associations were shown within the same basic experimental situation. Finally, Experiment 4 found evidence of the formation of the higher order association S^D(R → O) in human instrumental conditioning.     

Glucocorticoid-induced impairment of long-term memory retrieval in rats: an interaction with dopamine D2 receptors

This study investigated glucocorticoid-dopaminergic interactions in modulating retrieval of long-term memory in an inhibitory avoidance task. Young adult male rats were trained in one trial inhibitory avoidance task (0.5 mA, 3 s footshock). On the retention test given 48 h after training, the latency to re-enter the dark compartment of the apparatus was recorded. Systemically administered corticosterone (1 or 3 mg/kg) given to rats 30 min before retention testing impaired their memory retrieval, but the lower dose was more effective than the higher one. Administration of the dopamine (DA) D2 receptor antagonist sulpiride (6 or 20 mg/kg) 30 min before corticosterone attenuated the impairing effects of corticosterone (1 mg/kg) on memory retrieval. Administration of the DA D1 receptor antagonist SCH23390 (25 or 50 microg/kg) had no effect on corticosterone-induced impairment of memory retrieval. Further, applied doses of sulpiride or SCH23390 alone were ineffective in modulating memory retrieval. These findings provide evidence for the existence of an interaction between glucocorticoids and DA D2 receptor on memory retrieval process.     

Instrumental rationality in psychopathy: implications from learning tasks

Whether psychopathic offenders are practically rational has attracted philosophical attention. The problem is relevant in theoretical discussions in moral psychology and in discussions concerning the appropriate social response to the crimes of these individuals. We argue that classical and current experiments concerning the instrumental learning in psychopaths cannot directly support the conclusion that they have impaired instrumental rationality, construed as the ability to transfer motivation by means-ends reasoning. We claim that these experiments appear to show that psychopaths in certain circumstances are not aware of the relevant means for their ends. Moreover, we suggest how further empirical research could help to settle the issue.     

Gravity is not the only ruler for falling events: Young children stop making the gravity error after receiving additional perceptual information about the tubes mechanism

Young children seem to operate under the assumption that objects always fall in a straight vertical line. When asked to search for a ball dropped down an S-shaped opaque tube, they repeatedly search directly below. Hood proposed that children have difficulty in inhibiting their prepotent expectation that objects fall in a straight line (Hood, 1995). We asked whether the inability to inhibit this prepotent response is the only factor determining children’s performance on the tubes task. In one condition the openings to the tubes were covered by chimneys, whereas in another condition the openings were visible. When first tested with the apparatus, children performed better when the openings were visible. Furthermore, children’s performance on equally complex configurations (i.e., with or without chimneys) was modulated by their previous experience. Thus, children’s understanding of the tubes mechanism seems to play an important role in addition to inhibitory control.