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)     

Hormonal dissociation of limbic lesion effects on shuttle box avoidance in rats.

In a study with a total of 57 male albino Holtzman-derived rats, Ss with septal or hippocampal lesions showed facilitated acquisition of a shuttle box avoidance response compared to normal controls. Ss with septal lesions were also highly resistant to extinction compared with normal Ss. When the same lesion effects were examined in hypophysectomized Ss, the Ss with septal lesions continued to show facilitated performance, and Ss with hippocampal lesions performed no differently than nonoperated controls. These findings are consistent with the hypothesis that the facilitated avoidance performance found in rats with hippocampal lesions is attributable to lesion-induced changes in hypophyseal activity, but similar changes induced by septal lesions are not. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suppressive and enhancing effects of footshock on food-reinforced operant responding following septal lesions in rats.

Measured effect of septal lesions on suppression of an intermittently food-reinforced lever press by contingent and noncontingent footshock, using a total of 48 experimentally naive male hooded Lister rats in 2 experiments. Ss with septal damage maintained higher response rates than did intact Ss under both contingent and noncontingent shock. Furthermore, the difference in suppression produced by the contingent and noncontingent conditions was approximately the same for the experimental Ss and controls. In Exp II performance was measured during counter-conditioning in which the correlation between contingent shock and positive reinforcement was varied. Ss with septal lesions responded at higher rates than did controls. When only reinforced responses were punished, this lesion-induced elevation represented an increase above baseline performance without punishment. This finding suggests that the effect of septal damage on appetitive instrumental performance cannot be due solely to a deficit in response inhibition. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strain differences in avoidance conditioning as a function of the classical CS-US contingency.

Examined rates of shuttle box avoidance responding in 3 strains of rats as a function of classical and instrumental contingencies in 2 experiments. Ss were a total of 126 female albino Fischer, Lewis, and Long-Evans rats. In Exp I, during classical conditioned-stimulus-unconditioned-stimulus (CS-UCS) pairings in the absence of an avoidance contingency, there were large differences between the 3 strains in rates of anticipatory responding to the CS. The same pattern of differences was observed in Exp II when the avoidance contingency was added. None of the instrumental contingencies of CS termination, UCS termination, or the avoidance contingency differentially affected the strains. Classically elicited anticipatory responses and their compatibility with the required avoidance response were viewed as central factors in both the acquisition and maintenance of skeletal avoidance responses. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Type of start box and goal box distinctiveness in self-punitive running of rats.

A total of 96 male Sprague-Dawley rats were first trained to escape shock in an alley by running to a safe goal box. In Exp I either a trapdoor-floored start box or a guillotine-door start box was used in different groups. In extinction, nonpunished and punished subgroups were tested in each of the start-box conditions. Punishment produced faster running speeds than nonpunishment (self-punitive effect) only with the trapdoor. The trapdoor start box was used in Exp II, and independent groups of Ss were trained to escape to a goal box that was either very dissimilar or similar to the shock area. Nonpunished and punished subgroups were extinguished in each goal box condition. Self-punitive running was more likely with the dissimilar goal box. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Punishment and the length of non-shock confinement during the extinction of avoidance.

Groups of 72 male Sprague-Dawley rats, trained to avoid in an alley with 3 distinct chambers, spent either 2, 15, or 30 sec. in the safe or goal chamber (GB) during extinction, with the remainder of the constant 150-sec intertrial interval (ITI) spent in the start box (SB). 1/2 the Ss of each group were punished (shocked) in the middle chamber during extinction, 1/2 were not. It was found that (1) the longer the goal confinement, the greater the resistance to extinction; regular extinction groups extinguished faster than the punished; and (3) there was no significant interaction between GB confinement and the punishment variable. During extinction in Exp. 2 there were 2 levels of goal confinement (2 vs. 30 sec.), equal time spent in SB in all groups, a constant ITI of 62 sec., and punishment vs. no punishment. 48 male Sprague-Dawley rats served as Ss. As anticipated, punishment prolonged extinction only for the 30-sec GB confinement; the other 3 groups extinguished at approximately the same rate. The concept of short-latency "relief" was invoked to explain this significant interaction. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sidman avoidance performance and response suppression in rats with septal lesions.

Ran 10 male Long-Evans hooded rats with septal lesions on 3 Sidman avoidance schedules which differed only in length of response-shock (RS) interval. Of the 5 septal Ss run on postoperative acquisition, all emitted responses at lower rates than the 5 controls, maintained shock rates equivalent to those of controls, and distributed their responses more efficiently than controls. Successive reductions in length of the RS interval produced suppression of avoidance responding in all Ss. However, for septal Ss, more sessions and a shorter RS interval were required to suppress avoidance responding. Performance of 5 Ss given preoperative experience was not changed by septal ablation. Both the lower response rate and the difficulty in suppressing avoidance responding are interpreted in terms of a deficit related to acquisition of stimulus control by conditioned aversive stimuli. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aggression, avoidance, and reaction to novel environments in female rats with ventromedial hypothalamic lesions.

In an experiment with 30 adult female Sprague-Dawley rats, lesions in the ventromedial hypothalamus of 20 Ss (a) increased the probability of pain-elicited aggressive responses; (b) caused a loss of dominance in a situation where fighting was elicited by food competition and territorial defense; (c) did not change interspecies aggressive reactions; (d) facilitated acquisition of avoidance responses in a shuttle box; (e) increased locomotor activity and decreased latency of feeding behaviors in novel environments; and (f) resulted in an increase in locomotor activity in response to the introduction of shock in the shuttle box, in contrast to a decrease seen in controls. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Some behavioral effects of olfactory bulb damage in the rat.

Conducted 5 experiments in which male Holtzman rats (N = 50) with either olfactory bulb or septal lesions were tested on position-habit reversal, nonappetitive passive-avoidance, 1-way avoidance, and 2-way avoidance tasks. Ss with septal damage exhibited the expected behavioral abnormalities on all tasks. Ss with bulbar damage were deficient on 1-way avoidance, were facilitated on 2-way avoidance, and could not be distinguished from the normal Ss on the other 2 tasks. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Running-wheel avoidance behavior following septal area lesions in rats.

Studied acquisition of a running-wheel avoidance response in 52 male Wistar rats with (a) septal lesions, (b) septal and postcommissural fornix lesions, or (c) septal, postcommissural fornix, and anterior thalamic damage. Ss with lesions confined to the septum were deficient in acquiring the avoidance response compared with both normal Ss and Ss with the more posterior lesions. Ss sustaining combined septal-fornical and septal-fornical-thalamic lesions did not differ from normal Ss or from each other in their acquisition scores. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of intertrial reinstatement of training stimuli on complex maze learning in rats: Evidence that "acquisition" curves reflect more than acquisition.

In Exps I–III (224 male Sprague-Dawley rats), Ss were run in a complex maze to escape weak footshock or to approach an appetitive reinforcer. Extramaze intertrial reinstatement of the same reinforcer as that used in training was found to enhance subsequent maze performance. Exp IV (80 Ss) determined that appetitively and aversively motivated performance benefitted from brief intertrial exposures to the start box of the maze. In Exp V (64 Ss), a facilitatory effect indicated that memory trace activity need not be maintained between training and reinstatement or between reinstatement and subsequent training. Exp VI (80 Ss) examined the effects of reinstatement at the beginning, middle, or end of 5-min intertrial intervals and found enhanced performance in the last 2 conditions. Exp VII (24 Ss) established that 4 successive reinstatement treatments without interpolated training trials were no more beneficial than a single reinstatement. Exp VIII (16 Ss) determined that forgetting had occurred over the standard 5-min interval between training trials. Exp IX (32 Ss) found that reinstatement alleviated forgetting that had already transpired. (49 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Open-field and avoidance behavior after neostriatal lesions in male and female rats.

The behavioral effects of lesions of the anterodorsal or posteroventral parts of the caudate-putamen were studied in 2 experiments with a total of 115 male and 101 female adult albino Holtzman rats that were gonadectomized or left untreated prior to brain surgery. Anterodorsal (ADC) lesions consistently impaired acquisition of 1-way avoidance behavior and tended to interfere with the development of a 2-way avoidance response; comparable effects were observed in gonadectomized and intact Ss of both sexes. By contrast, ADC lesions increased activity in the open field only in intact females and increased rearing only in ovariectomized females. Posteroventral caudate (PVC) lesions caused transient aphagia and adipsia in both sexes but did not consistently affect open-field activity or the acquisition of 1-way avoidance responses by either sex. These lesions profoundly impaired acquisition of shuttle box avoidance responses by intact males. By contrast, castrated males and intact and ovariectomized females with PVC lesions avoided normally in the shuttle box. Results suggest that localization of behavioral functions within the striatum differs with the sex of the S, in part because of activational effects of gonadal hormones. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fornix lesions, plasma ACTH levels, and shuttle box avoidance in rats.

In Exp I, which used 90 male hooded rats as Ss, the consequences of fornix lesions (FLs) for partial acquisition, and performance at 3 postacquisition time intervals, of shuttlebox avoidance were tested. FL Ss achieved criterion performance more rapidly than controls. The performance of controls was depressed when they were tested 1 hr after acquisition ("Kamin effect"), but the performance of FL Ss was not impaired. The possibility that FLs altered plasma ACTH concentrations at the intervals after avoidance training used in Exp I was examined in Exp II (96 Ss). Plasma ACTH concentrations were elevated in FL Ss compared with unoperated and sham-operated controls, both immediately and 1 hr after avoidance training. Plasma ACTH levels were not elevated in FL Ss following either stress alone or 24 hrs after avoidance training. Results indicate that FLs cause elevated ACTH levels in rats after avoidance training that are responsible for elimination of the Kamin effect. In addition, data support the contention that enhanced acquisition of 2-way active avoidance by rats with FLs or hippocampal damage might be attributable to increased plasma ACTH levels. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of exposure to conditioned stimulus and control of its termination in the extinction of avoidance behavior.

Describes 2 experiments in which, following signaled shuttle box avoidance training, a total of 52 female Fischer344 rats were exposed to the conditioned stimulus (CS) during no-shock treatment trials and subsequently tested during extinction trials in which shock was also absent. In Exp I, Ss that could control the termination of the CS during treatment responded significantly more often during extinction than yoked partners that received the same pattern and duration of CS exposure but could not control its termination. Exp II revealed that the probability of responding during extinction was a decreasing function of the duration of CS exposure during treatment. Thus, in the absence of shock, both lack of control over CS termination and increasing CS exposure each independently facilitated the weakening of well-established avoidance responses. (21 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)     

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)     

Effect of septal area damage and base-line activity levels on conditioned heart-rate response in rats.

Exp. I subjected 7 unrestrained male Long-Evans rats with septal area lesions and 8 nonoperated controls to Pavlovian heart-rate conditioning with footshock as the UCS. Experimental Ss displayed lower degrees of tachycardia to both the CS and UCS than did controls, but there were no significant differences in amount of skeletal movement. In Exp. II, 6 control and 6 septal-damaged Ss received CS-shock pairings while lever pressing for food and while not lever pressing. There was no difference in conditioned suppression, but less conditioned tachycardia was again seen in experimental Ss, indicating dissociation between the 2 measures of conditioning. All Ss exhibited greater tachycardia during the non-lever-pressing condition, illustrating the effect of base-line activity on conditioned heart-rate responses. (24 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Collateral behaviors and the DRL deficit of rats with septal lesions.

Trained a total of 31 male Long-Evans hooded normal and septally-lesioned rats to lever press for food on a DRL 20-sec schedule in either a conventional operant chamber or 1 containing wood blocks and cardboard strips. The DRL behavior of normals trained in modified chambers was most efficient, and that of Ss with septal lesions trained in conventional chambers was least efficient. After 35 hr. of training, normals tested in conventional chambers and Ss with septal lesions tested in modified chambers did not differ significantly. Ss chewed the blocks and cardboard, and prevention of these collateral behaviors reduced DRL efficiency. Results show that colalteral behaviors facilitate the development of efficient DRL behavior and indicate that the DRL deficit of rats with septal lesions can be modified. (17 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)     

Time course of effects of septal lesions on avoidance, response suppression, and reactivity to shock.

Conducted 4 experiments with a total of 99 male albino Sprague-Dawley rats with septal lesions and 76 sham-operated controls. Ss tested 5 or 10 days, but not 2 days, after septal lesions acquired a 2-way conditioned avoidance response faster than controls. Punishment in a passive-avoidance test was least effective in suppressing milk-licking 2 days after septal lesions, and increased in effectiveness as a function of time after surgery. All experimental Ss were significantly more reactive to footshock than controls in a jump-flinch test. Results support the hypothesis that different aversively-controlled behaviors are mediated by different mechanisms within the septum. (31 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)