Genetic differences in avoidance learning by Rattus norvegicus: Escape/avoidance responding, sensitivity to electric shock, discrimination learning, and open-field behavior.

Studied the behaviors of Long-Evans rats selectively bred for either good (SHA line) or poor (SLA line) shuttle box avoidance learning. The results of Exp I indicated that the phenotypic difference in avoidance learning was not associated with differences in speed of escape or avoidance responding. Differences between the lines in frequency of intertrial responses (ITRs), which appeared during training but not during pretest, suggest that ITRs in Ss of the low-avoidance SLA line were more suppressed by electric shock than in Ss of the high-avoidance SHA line. This result suggests that SLA Ss may be more emotionally responsive than SHA Ss. Exp II demonstrated that the Ss of the 2 lines did not differ in absolute sensitivity to electric shock, and Exp III showed that the poor performance of the SLA line was not due to an inability to learn. Ss also provided evidence that the poor avoidance learning by SLA Ss was due to their emotional reactivity. Observations of open-field behavior in Exp IV were consistent with this hypothesis. It is concluded that the major consistent correlate of the phenotypic difference in avoidance learning was greater emotionality or emotional reactivity in SLA than in SHA Ss. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the amygdala and dorsal raphe nucleus in mediating the behavioral consequences of inescapable shock

It has been argued that exposure to inescapable shock produces later behavioral changes such as poor shuttle box escape learning because it leads to the conditioning of intense fear, which later transfers to the shuttle box test situation and interferes with escape. Both fear, as assessed by freezing, and escape were measured in Sprague-Dawley rats 24 hr after exposure to inescapable shock. Lesions of the basolateral region and central nucleus of the amygdala eliminated the fear that transfers to the shuttle box after inescapable shock, as well as the fear conditioned in the shuttle box by the shuttle box shocks. However, the amygdala lesions did not reduce the escape learning deficit produced by inescapable shock. In contrast, dorsal raphe nucleus lesions did not reduce the fear that transfers to the shuttle box after inescapable shock, but eliminated the enhanced fear conditioning in the shuttle box as well as the escape deficit. The implications of these results for the role of fear and anxiety in mediating inescapable shock effects are discussed.     

Septal ablation in the rat and bar pressing under appetitive and aversive control.

Assigned 6 male hooded rats with bilateral septal lesions and 3 Ss with bilateral cortical control lesions to bar-press in a successive discrimination (go, no-go) task. Over successive experimental conditions, responding was maintained by the following reinforcers: food, shock escape, shock avoidance, concurrent food reinforcement and shock avoidance, and, once again, food. Ss with septal lesions responded to the no-go stimulus at higher rates than did controls only under the simple food-reinforcement conditions. Results suggest that disinhibition of bar pressing following septal ablation in rats may occur with appetitive and not with aversive schedules of reinforcement. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of pretraining compatible and incompatible responses on subsequent one-way and shuttle-avoidance performance in rats.

Conducted 6 experiments with male Holtzman rats. A single noncontingent footshock was found to facilitate subsequent one-way and shuttle avoidance if the CS in preshock and avoidance training was the same. If the to-be-established instrumental response was punished during preshock, or if Ss were required to run toward the CS paired with shock during pretraining, the facilitative effects of preshock were eliminated. Facilitation by a single preshock was not enhanced if shock was escapable, regardless of the CSs, task, or whether escape was immediate or delayed. If Ss received 10 one-way escape trials, the beneficial effects of preshock on one-way and shuttle avoidance were enhanced. In contrast, shuttle-escape training produced no such beneficial effects on avoidance performance. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Domestication, sophistication, and avoidance in Norway rats.

Administered successive 1-way and 2-way avoidance tasks which included treatments of postweaning handling to docility, prior learning sophistication, and differential shock intensity. In this 2-stage paradigm, with 32 wild and 32 hooded Long-Evans rats, escape and avoidance behaviors of wild and laboratory Ss were indistinguishable. Sophistication in laboratory-learning experience and high shock contributed significantly to the performance of both wild and domestic Ss in 1-way, but not 2-way, avoidance. In contrast, effects of handling were apparently negligible. Findings do not support the notion of degeneracy of learning ability in the domesticated rat. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure to learn to escape by rats previously exposed to inescapable shock is partly produced by associative interference.

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) 2010 APA, all rights reserved)     

Failure to learn to escape in rats previously exposed to inescapable shock depends on nature of escape response.

Results of previous studies show that dogs exposed to inescapable shocks in a Pavlov harness subsequently fail to learn to escape shock in a shuttle box. The present 6 experiments attempted to replicate this finding with male Sprague-Dawley rats (N = 182). In agreement with many previous investigations, Exp I found that Ss exposed to inescapable shock did not fail to learn to escape in a shuttle box. Exp II, III, and IV varied the number, intensity, and temporal interval between inescapable shocks and did not find failure to learn in the shuttle box. An analysis of responding in the shuttle box revealed that Ss shuttled rapidly from the very 1st trial, whereas dogs acquire shuttling more gradually. Exp V and VI revealed that Ss exposed to inescapable shock failed to learn to escape when the escape response was one that was acquired more gradually. Exp V utilized a double crossing of the shuttle box as the escape response and Exp VI utilized a wheel-turn response. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differentiation of escape and avoidance responding in rats.

Examined escape and avoidance performance in 144 female Holtzman albino rats by factorially arranging immediate or postponed CS and UCS termination with shuttle or bar-press escape and avoidance responses. High levels of avoidance responding occurred only when the shuttle response (running) was both the escape and avoidance response, perhaps reflecting that rats are prepared to run but contraprepared to bar press when threatened by aversive stimulation. In addition, postponed UCS termination reduced avoidance performance drastically while CS termination conditions were without effect. Measures of UCS duration and clock terminations also indicated that immediate UCS termination was superior to postponed termination but additionally showed that this was so because postponed termination seriously impaired escape behavior. Results have particular relevance for how escape responses become anticipatory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potentiation, overshadowing, and prior exposure to inescapable shock.

Four experiments are reported which explore the possibility that prior exposure to inescapable shock alters the way in which animals process information from responding during subsequent escape training. The stimulus consequences of responding were manipulated in each experiment. Rats received escapable shock, yoked, inescapable shock, or no shock prior to fixed ratio-2 (FR-2) shuttle escape training. A novel change in illumination following each shuttle response had opposite effects on inescapably shocked and control subjects. It dramatically improved the performance of inescapably shocked rats but impaired the performance of restrained subjects. The signal had no effect on escape trained animals. Response-produced auditory cues following each lever press on an FR-3 lever-press escape task were also observed to improve learning in inescapably shocked rats but to impair learning in restrained controls. The relation between lever pressing and the exteroceptive cue was manipulated. The exteroceptive cue enhanced learning in inescapably shocked rats when any two of the three required lever presses produced the cue. In contrast, the performance of restrained animals was impaired whenever the third response of the FR-3 produced the cue. Otherwise performance was unimpaired. The implications of these results are discussed with respect to the phenomena of potentiation and overshadowing, as well as to ways in which prior exposure to inescapable shock might alter information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of genotype and postnatal experiences on activity, avoidance, shock threshold, and open-field behavior of rats.

Studied the effects of postnatal experience in 6 experiments on the activity, avoidance, shock threshold, and open-field behavior of 91 selectively-bred Ss from high-avoidance (RHA/Lu) strains and 93 from low-avoidance (RLA/Lu) strains. Significant differences were found between postnatal experiences in shuttle box activity, but strain differences were not significant. The high-avoidance Ss acquired avoidance learning significantly faster and had lower shock thresholds than the low-avoidance Ss. However, postnatal experience had significant effects on avoidance and shock threshold only in the high-avoidance Ss. No significant strain differences were found in open-field behavior, and the postnatal experience effects showed only higher order significant interactions. Results are discussed in the framework of quantitative genetics and a direct-action hypothesis of postnatal experience. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aversive conditioning in neonatal kittens.

Trained 45 kittens less than 10 days of age to crawl over a barrier in a 1-way shuttle box either to escape or avoid pressurized air. Both instrumental escape and avoidance learning occurred. Escape performance was an increasing negatively accelerated function of air pressure. Avoidance behavior was not as stable or of the same form as that previously observed in infant dogs. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Therapeutic effects of exercise: Wheel running reverses stress-induced interference with shuttle box escape.

Exercise can reduce symptoms of depression and anxiety in humans, but therapeutic effects of exercise in an animal model of stress-related mood disorders have yet to be demonstrated. In the current study, the authors investigated the ability of wheel running to reverse a long-lasting interference with shuttle box escape produced by uncontrollable stress. Rats who remained sedentary following uncontrollable foot shock demonstrated robust conditioned freezing behavior to the stressor environment and deficits in shuttle box escape learning. Voluntary access to running wheels for 6 weeks, but not 2 weeks, following uncontrollable foot shock reduced the expression of conditioned freezing and reversed the escape deficit. Results demonstrate a long-lasting interference with shuttle box escape that can be reversed by exercise in a duration-dependent fashion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of response restriction during exposure to inescapable shock upon subsequent one-way and shuttle-avoidance performance in rats.

Investigated the effects of signaled inescapable shock on subsequent avoidance performance in 3 experiments with male Holtzman rats (N = 188). Exp I indicated that prior shock exposure (PSE) facilitated 1-way and shuttle avoidance. When Ss were preshocked in a harness so that free mobility was not possible, the facilitative effects of PSE on shuttle, but not 1-way avoidance performance, were largely reduced. Exp II indicated that activity during CS periods following PSE was greater among unrestrained than restrained Ss. Exp III showed that immobilization via injection of succinylcholine chloride did not affect the facilitative effects of PSE relative to that of Ss preshocked in a harness. Results are interpreted in terms of response repertoire changes produced by PSE in conjunction with the response requirement of the avoidance task. (French summary) (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of varying active/passive shock levels in shuttle box avoidance in rats.

Ran 60 male Sprague-Dawley albino rats in a shuttle box with 3 levels of shock intensity-high (H), medium (M), and low (L)-which varied independently on each side. This yielded 6 groups defined by the shock level in the 2 chambers: H-H, M-M, L-L, H-L, H-M, M-L. Results indicate that when active shock level was held constant, avoidance behavior was a function of passive shock level, with lower passive shock level producing higher levels of avoidance. Avoidance was not a function of active shock level when passive shock level was held constant. 10 controls were run using a unidirectional paradigm, and avoidance was not found to be a function of the active shock level. Results are interpreted as emphasizing the role of passive avoidance in bidirectional shuttling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Daily fluoxetine administration impairs avoidance learning in the rat without altering sensory thresholds

1. Male rats given daily intraperitoneal injections of fluoxetine (10 mg/kg) were slower to escape foot shock by jumping a low barrier. 2. When switched to a shuttle task requiring two crosses to terminate shock, the FLU-treated animals failed to learn in 55 trials. 3. A second experiment found FLU-treated animals could learn a one-way avoidance response, but were significantly slower to learn than control animals. 4. FLU-treated animals were no different than controls on tests of sensory thresholds for foot shock or heat. 5. Tests of motor behaviors revealed no differences in latency to traverse a narrow beam to reach a goal box, however FLU-treated animals were less active in an open field. 6. Several hypotheses can account for these data, the most promising being that a central motivational system (fear) is less active in FLU-treated animals.     

DSP4 (N-2-chloroethyl-N-ethyl-2-bromobenzylamine), a new noradrenaline neurotoxin, and stimulus conditions affecting acquisition of two-way active avoidance.

Several CS and UCS variables known to affect the rate of acquisition of the 2-way active avoidance task were investigated in rats treated with the novel selective noradrenaline neurotoxin DSP4 (50 mg/kg, ip). 234 male Sprague-Dawley rats were used in 6 experiments. Although the DSP4 Ss did not demonstrate the linear relation between CS duration and avoidance acquisition to the same extent as controls, their avoidance performance was as drastically disrupted as that of the controls both by preexposure to the CS and by increasing levels of shock intensity. DSP4 Ss also evidenced fear retention for the shuttle box cues previously associated with inescapable shocks to as marked a degree as control Ss. Biochemical data indicated profound noradrenaline depletion in the cortex and hippocampus and a lesser depletion in the hypothalamus. Findings offer a behavioral characterization of the consistent DSP4-induced impairment of 2-way active avoidance acquisition. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of interference with the speed and accuracy of escape produced by inescapable shock.

Benzodiazepines and naltrexone administered before inescapable shock block behavioral consequences of the inescapable shock such as poor shuttle box escape, reduced activity in reaction to shock, reduced social interaction, and so on. Anxiogenic β-carboline derivatives such as FR-7142 can produce these effects by themselves. In the present study, neither diazepam nor naltrexone had any effect on the interference with Y-maze choice escape accuracy produced by inescapable shock even though they both eliminated the reduction in Y-maze escape response speed produced by inescapable shock. Analogously, FG-1742 did not lead to a reduction in Y-maze choice escape response accuracy even though it did show escape responding. These data imply that inescapable shock interferes with escape choice learning and escape response speed by different mechanisms, the former not involving fear-anxiety processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Studies of the extinction of avoidance responding through the massing of trials.

Performed 2 experiments in an automated 1-way avoidance box for rats. Exp. I, with 44 Sprague-Dawley female albino rats, was concerned with the effect of shock intensity on the rate of extinction using the massing-of-trials technique during extinction. Most measures of avoidance learning were not affected by shock intensity, and the rate of extinction was also not significantly affected. Exp. II, with 44 Ss similar to those in Exp. I, examined the effect of the duration of the extinction ITI on the rate of extinction. A critical duration is suggested by results. (French summary) (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schizophrenic discrimination learning as a function of aversive social and physical reinforcement.

60 schizophrenics comparable in important psychopathological variables (e.g., Inpatient Multidimensional Psychiatric Rating Scale and the Premorbid History-Phillips Prognostic Rating Scale) to Ss in other similar studies were compared on a discrimination learning task with noxious physical reinforcement (intense white noise at 91–94 db) under experimenter (E)-present conditions with motivational instructions and E-absent conditions with neutral instructions. Aversive reinforcement was delivered on a response contingent basis for avoidance and escape training under both social conditions. Long-term effects were evaluated 3 consecutive learning tasks: before, during, and following the 6 reinforcement conditions. Results provide strong confirmation that social factors in the E–S relationship determine the speed of learning throughout. Regardless of physical punishment or the reinforcement paradigm (avoidance or escape), Ss learned significantly faster in the E's presence with motivational instructions both during and after the reinforcement phase. The theoretical implications of what is called biological motivation were found to be insufficient grounds for ordering the data. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitation and nonfacilitation of active avoidance behavior of rats with septal lesions in the shuttle box and running wheel.

Hypothesized that facilitation of avoidance performance of rats with septal lesions occurs only in tasks that punish responses having the same topography as the avoidance response, such as intertrial responses, or tasks that have aversive consequences for making the avoidance response, such as a brightly illuminated safe compartment. 28 male Sprague-Dawley rats (Exp I) were trained in 2 shuttle box tasks, and 24 (Exp II) were trained in 2 running-wheel avoidance tasks under conditions of punishment or nonpunishment of intertrial responses. Ss with septal lesions performed better than controls in both the shuttle box and the wheel tasks when intertrial responses were punished. When intertrial responding was not punished, experimental and control groups did not differ in avoidance performance. Avoidance performances of punished and unpunished Ss with septal lesions did not differ from each other or from unpunished controls in either wheel or shuttle box tasks. Results are discussed in the context of the species-specific defense reaction (SSDR) avoidance theory of R. C. Bolles (see record 1970-04813-001). It is suggested that septal lesions interfere with the suppression of ineffective SSDRs. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)