Conditioning and extinction of avoidance and escape behavior in neonatal dogs.

Ran 16 neonatal purebred beagles for 6.5 days in a 1-way shuttle box with cold air as the aversive stimulus. 8 Ss started at 1 day of age and 4 each started at 2 and 3 days of age. 8 Ss received escape conditioning and 8 received avoidance conditioning. Following this training, both groups were given a series of extinction trials. Both escape and avoidance conditioning and extinction were obtained. Findings are comparable to previous avoidance findings in neonatal dogs and superior to findings on neonatal mice and kittens. Results display quantitative properties found in studies of adult rats and especially adult dogs. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of acquisition training schedule on extinction and reinstatement of cocaine self-administration in male rats.

Partial reinforcement is known to increase resistance to extinction (Rn) relative to training with continuous reinforcement. This phenomenon, referred to as the partial reinforcement extinction effect, is one of the most robust in learning and conditioning studies. Experiment 1 investigated manipulations known to affect the partial reinforcement extinction effect and determined their possible relevance for drug use patterns. Male rats received intravenous cocaine self-administration training under partial reinforcement (FR-10) training or continuous reinforcement (FR-1) conditions with either a low (0.25 mg/kg infusion) or a high cocaine dose (1.00 mg/kg infusion). Animals were placed on an extinction (recurrent nonreward) schedule for 10 days (1-hr sessions) prior to being tested for cue-induced reinstatement (single 2-hr session). Experiment 2 involved acquisition of cocaine self-administration under FR-1 conditions of short training (15 days) or extended training (30 days) with a low dose (0.25 mg/kg infusion) or a medium dose (0.50 mg/kg infusion) of cocaine reward prior to extinction or reinstatement. Experiment 1 showed that rats trained with FR-10-high dose outcomes exhibited greater Rn than the remaining groups. Additionally, FR-10-high dose and FR-10-low dose rats were more likely to return to active drug seeking during the reinstatement test. In Experiment 2, rats trained under FR-1-medium dose conditions were more persistent during extinction following short acquisition training than comparable rats experiencing extended acquisition training. The reinstatement test was conducted following extinction, in which it was observed that overtraining under FR-1-medium dose reward schedules resulted in a decrease in the tendency to return to active drug seeking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric transfer of extinction of the active avoidance reaction in rats.

Employed cortical spreading depression (CSD) in 38 hooded Druckrey rats to study the lateralization of extinction of a jumping avoidance reaction. Under unilateral CSD, 181 nonreinforced trials were needed to extinguish the avoidance reaction acquired in 3 100-trial sessions of intact-brain training. During a 2nd extinction session, either with the same or with the contralateral hemisphere depressed, the mean number of trials to the extinction criterion (9 avoidance reactions in 10 consecutive trials) was 39 or 186, respectively. 5 extinction trials performed with the brain intact 1 hr before extinction with contralateral CSD decreased the number of trials to extinction to 98. Thus, extinction of active avoidance can be lateralized and interhemispherically transferred in the same way as acquisition of this habit. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Backward sensory preconditioning.

In Experiments 1 and 2, rats received initial training in which two neutral events were presented as a serial compound (A?→?X). Subsequent training with A as a signal for shock was found to endow X with the ability to evoke the conditioned response of suppression. Experiment 2 also showed that responding to X was diminished if, prior to testing, Stimulus A underwent extinction. Two possible mechanisms for these findings are considered: (a) that X elicits responding through the associative chain X-A-shock, and (b) that A activates a representation of X that gains direct associative strength during conditioning with A and loses it during extinction of A. Experiment 3 demonstrated that an X-shock association established after initial A?→?X training can be extinguished by nonreinforced presentations of A. These results suggest that associatively evoked representations of stimuli can enter into associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress enhances excitatory trace eyeblink conditioning and opposes acquisition of inhibitory conditioning

Exposure to a brief, stressful event is reported to facilitate classical eyeblink conditioning in the male rat (Rattus norvegicus) by use of a delay paradigm in which the conditioned stimulus (CS) and unconditioned stimulus (US) overlap and coterminate. This study examined the effects of stress on trace conditioning, a task in which the CS and US were separated by 500 ms. Experiment 1 showed that exposure to brief (1 s), low-intensity (1 mA) tailshocks facilitated acquisition 24 hr later. Experiment 2 showed that stressor exposure did not affect retention or extinction of trace conditioning in rats that were stressed after acquisition. Experiment 3 showed that exposure to the same stressor opposed acquisition of inhibitory conditioning. These results suggest that exposure to a stressful event persistently facilitates acquisition of trace conditioning and enhances a bias toward acquiring positive versus negative associations.     

Persistence of runway performance after septal lesions in rats.

Assigned 32 male Wistar albino rats to groups receiving bilateral septal lesions or control operations. Septal lesions prevented the partial reinforcement extinction effect after 48 acquisition trials. Septal Ss showed increased resistance to extinction following continuous reinforcement but decreased resistance to extinction following partial reinforcement. Analysis of the acquisition data indicated that the lesions retarded the development of approach-avoidance conflicts associated with reward and nonreward. In a 2nd study, 16 septal and 16 control Ss received 96 acquisition trials. Extended training allowed the development of conflict responses under partial reinforcement, and the Ss with lesions were indistinguishable from controls during extinction. Following continuous reinforcement, septal lesions produced slower extinction of response. It is concluded that the lesions interfered with the development of feedback from frustration, approach-avoidance conflicts, and frustration tolerance. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of lesions to the hippocampus on contextual fear: Evidence for a disruption of freezing and avoidance behavior but not context conditioning.

The effects of ibotenic lesions of the hippocampus on conditioning to contextual cues during classical fear conditioning in rats were evaluated by (a) the amount of freezing elicited by contextual cues and (b) the relative avoidance of a shock compartment. In Experiment 1, lesions to the hippocampus had no effect on contextual freezing and marginally affected avoidance after repeated sessions. Experiment 2 showed that lesions to the hippocampus disrupted avoidance when tested after a single conditioning session, while leaving unaffected the acquisition of contextual freezing. Experiment 3 indicated that these lesions decreased the acquisition of contextual freezing when higher footshock intensity was used but had no effect on avoidance after repeated conditioning sessions. These results show that freezing and avoidance do not quantify context conditioning similarly. They further indicate that lesions to the hippocampus may disrupt the expression of these behaviors used as measures of context conditioning but not the acquisition of context conditioning per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reward magnitude in differential conditioning: Effects of sequential variables in acquisition and extinction.

Nine Sprague-Dawley male albino rats were randomly assigned to each of 5 groups. Three groups received differential conditioning to small (S) and large (L) reward. One group (LS) experienced L–S transitions, a 2nd group (SL) experienced S–L transitions, and a 3rd group (LS–SL) received the combined sequences of Groups LS and SL. Two control groups received only L or S trials. Negative contrast (slower speeds in the S-alley than the S control group had) was demonstrated for all 3 differential groups, and positive contrast (faster speeds in the L-alley than the L control group had) was demonstrated in Groups LS and SL, but not LS–SL. In extinction, Groups S and L showed the usual between-S differences in resistance to extinction (S more resistant than L); Groups LS and LS–SL also showed this effect, based on the within-S procedure. Group SL showed the opposite effect, which was predicted by an extension of the sequential hypothesis of extinction effects. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context extinction following conditioning with delayed reward enhances subsequent instrumental responding.

In Experiment 1, delayed reward generated low response rates relative to immediate reward delivered with the same frequency. Lister rats exposed to delayed reward subsequently responded at a higher rate in extinction if they received nonreinforced exposure to the conditioned context after instrumental training and prior to test, compared with animals that received home cage exposure. In Experiment 2, a signaled delay of reinforcement resulted in higher rates than an unsignaled delay. Nonreinforced exposure to the conditioning context elevated response rate for subjects in the unsignaled condition relative to a home cage group, but had no effect on response rates for subjects that had received the signaled delay. In Experiment 3, following an unsignaled reinforcement delay, groups receiving either no event or signaled food in the context responded faster in extinction than groups receiving no context exposure or unsignaled food. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial delay extinction effects within-subjects based on sequential manipulations.

Describes an experiment with 4 groups of 10 male albino Sprague-Dawley rats. 3 groups received partial delay of reward in 1 runway and immediate reward in a discriminably different runway followed by extinction to both runways. Group 1, which received transitions from delay to immediate reward in the partial-delay alley, showed greater resistance to extinction in the partial-delay alley than in the immediate alley. Groups that received transitions from delay to immediate reward in the immediate alley (Group 2) and in both partial-delay and immediate alleys (Group 3) showed no differential within-S extinction performance. A between-group, partial-delay extinction effect was found; all Ss experiencing delay showed greater resistance to extinction than Group 4 (controls) that received only immediate reward. Data are interpreted within the framework of E. J. Capaldi's sequential theory. However, an extension of sequential theory was needed to account for the nondifferential extinction performance of Group 2. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebellar cortical degeneration disrupts discrimination learning but not delay or trace classical eyeblink conditioning.

The authors investigated classical eyeblink conditioning in a relatively rare patient, B.R., with extensive cerebellar cortical atrophy and marked sparing of the dentate nucleus. Patient B.R.'s ability to acquire and extinguish simple associations (delay and trace conditioning tasks) as well as her ability to acquire more complex associations (temporal and simple discrimination tasks) were examined. There are 2 primary findings from this study. First, B.R. showed normal acquisition and extinction in delay and trace conditioning. Second, she demonstrated a complete inability to learn associative discriminations, even in the case of a simple 2-tone discrimination within the context of a delay paradigm. The latter finding was unexpected because of the sparing of her deep cerebellar nuclei. These data suggest that the cerebellar cortex, or pathways traversing cerebellar cortex, play an important role in classical eyeblink discrimination learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resistance to extinction in rats as a function of deprivation level and schedule of reward in acquisition.

Conducted 3 straight-alley investigations with 84 male and 44 female Holtzman albino rats. 2 levels of deprivation were combined factorially with 2 schedules of reward (50 or 100%) in acquisition. Deprivation level in extinction was equated. When extinction deprivation level was low either there was no difference in extinction due to acquisition deprivation level or groups trained under high deprivation were more resistant to extinction than groups trained under low deprivation, as they were when deprivation level was high in extinction. It is suggested that at least 2 factors influence resistance to extinction as a function of acquisition deprivation level deprivation-related stimuli and some factor which produces greater resistance to extinction following high deprivation in acquisition. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of warm-up effects during avoidance in wild and domesticated rodents.

Studied warm-up effects during free-operant avoidance in 5 Sprague-Dawley albino, 5 Long-Evans hooded, and 7 black rats and 8 Mongolian gerbils. Domesticated Ss (albino and hooded) received disproportionately large numbers of shocks early in the session (warm-up), while the distribution of shocks was substantially more uniform for the nondomesticated Ss. The 2nd phase of the experiment studied responding during 1-hr extinction periods in albino rats, as a function of the duration of an avoidance period which immediately preceded it. Responding during the 1st 10 min. of the extinction period was significantly influenced by the length of the avoidance period. Significant correlations were observed in most cases between extinction responses and avoidance time, avoidance responses, and shocks. Results are interpreted as supporting a motivational explanation of warm-up. (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classical differential and operant conditioning in rabbits (Oryctolagus cuniculus) with septal lesions.

12 normal New Zealand white rabbits and 12 with septal lesions received classical differential conditioning of the nictitating membrane response (NMR), followed by auditory generalization tests run in extinction. Although rate of acquisition and asymptotic responding to positive conditioned stimuli did not differ, septals responded more than normals to nonreinforced stimuli. Resultant decrements in differential conditioning could not be attributed to changes in auditory or shock thresholds or to increased spontaneous NMRs. Septals also responded at higher rates in both operant conditioning (barpresses reinforced with food pellets on a variable interval schedule) and extinction sessions. No difference in suppression in a passive avoidance task was found. Results are discussed in relation to R. A. McCleary's (1966) response disinhibition analysis of septal function, and an habituation hypothesis is considered. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reward magnitude and partial reinforcement effects in a single runway.

The partial reinforcement acquisition effect (PRAE) in running speeds and the frustration effect (activity following nonreward compared with reward) were measured simultaneously in an alley whose goal-box floor was a stabilimeter. Experimental groups of 9 male Charles River albino rats each received 50 or 100% reinforcement combined factorially with 3 magnitudes of reward (1, 3, or 9 pellets). A control group of 18 Ss was never rewarded. The size of the PRAE was a direct function of reward magnitude, and crossing of 50 and 100% curves was found for all alley segments, including the goal segment. The frustration effect (FE) was present by the 2nd day of training for the 3- and 9-pellet groups, and the size of the FE was directly related to reward magnitude. The present study is unique in that (a) the findings were free from the effects of reward contrast, (b) behavior antecedent to the goal indicated that incentive was effectively manipulated, and (c) an unrewarded control group was used. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of US intensity and number of CS-US pairings on maintenance of vicious-circle behavior in rats by secondary punishment.

By factorial arrangement, 8 groups of male hooded Long-Evans rats (N = 80) received either 3 or 15 buzzer presentations associated with a shock of 0, 55, 70, or 85 V in a conditioning apparatus. 1 other group was administered buzzer and shock presentations randomly paired in time; the final group had 15 pairings of buzzer and an 85-V shock. During extinction of a runway avoidance response, each group received continuous buzzer punishment except the final group, which received no buzzer. It was found that alley running speed and trials to extinction were increasing functions of shock intensity presented during fear conditioning. While the number-of-pairings variable was somewhat more equivocal in its effects, results largely substantiate expectations of a conditioned-fear interpretation of secondary self-punitive behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition and extinction of a shuttling response in honeybees (Apis mellifera) as a function of the probability of reward.

The effects of partial (intermittent) vs consistent reward on the acquisition and extinction of a shuttling response were studied in 3 experiments with foraging honeybees. Adding nonrewarded trials to rewarded trials (the equated-reinforcements design) improved performance in acquisition and increased resistance to extinction. Substituting nonrewarded trials for some rewarded trials (the equated-trials design), which had little effect on acquisition, also increased resistance to extinction but to a lesser extent than adding nonrewarded trials. Marked variations in the schedule of partial reward (the sequence of rewarded and nonrewarded trials) were without effect. The results are compared with those of analogous experiments on vertebrates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of punishing active avoidance in young and adult rats.

Examined whether age-related differences in suppression occur when a learned response is punished. 8 groups of weanling and adult male Holtzman rats (N = 96) received active-avoidance training and subsequent punishment for that response. Following active avoidance, Ss were assigned to a regular extinction group or to 1 of 3 punishment-delay (0-, 2-, or 10-sec.) groups, which received shock in the goal box. Although weanlings and adults were equivalent in active-avoidance acquisition, under the immediate punishment condition immature Ss required significantly more trials to learn passive avoidance. A delay-of-punishment gradient was obtained in adults but not in weanlings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Species generality of within-subjects reward magnitude effects.

12 female pigtail, stumptail, and squirrel monkeys and 4 female Holtzman albino rats were given acquisition, extinction, and reacquisition training in a discrete-trials 2-lever spatial discrimination situation. In acquisition the left and right levers were associated with 5- and 1-pellet rewards, respectively, and in reacquisition, response to either lever produced 5-pellet reward. The 4 species showed similar patterns of preference for the 5-pellet lever on 2-lever choice trials and differential responding on 1-lever forced trials in acquisition, and similar within-Ss extinction effects which were at variance with the typical crossover of large- and small-reward extinction curves in between-groups reward magnitude studies with rats. Species differences appeared in over-all relative rate of extinction, with the macaques showing the fastest extinction, and in the degree to which historical effects of acquisition conditions appeared and persisted in reacquisition. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned avoidance of flavors signaling reduction in a nutrient.

Food-deprived rats learned to avoid a flavor negatively correlated with access to a rich nutrient, 20% maltodextrin (20M) solution. This avoidance in two-bottle choice tests was produced by training consisting of either an unpaired condition where sessions of unflavored 20M were intermixed with sessions of 2 or 3% maltodextrin (2M or 3M) flavored with salt (Experiment 1) or almond (Experiments 3 and 4) or a differential conditioning procedure where one flavor was mixed with 20M and another with 2M (Experiment 2). Avoidance was counter-conditioned by mixing the target flavor with 20M (Experiment 1), generalized to a neutral context (Experiment 3), and displayed strong resistance to extinction (Experiment 4). The results demonstrated that food avoidance learning can occur in the absence of an aversive unconditioned stimulus and indicated that unpaired control groups and differential conditioning procedures may be misleading in flavor preference learning research when further control conditions are absent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)