Facilitative and disruptive effects of prior exposure to shock on subsequent avoidance performance.

Subjected 40 male rats from each of 5 strains to 10 signaled inescapable 1-ma shock presentations. Shock facilitated subsequent 1-way and shuttle-avoidance performance (1-ma shock) in Charles River hooded, Wistar, Holtzman, and Sasco Ss, but did not significantly affect avoidance learning in Sprague-Dawley Ss. A 2nd experiment employing 120 male Holtzman rats indicated that inescapable shock of 1 ma. facilitated subsequent 1-way and shuttle-avoidance performance, while exposure to shock of 2 ma. facilitated 1-way and interfered with shuttle-avoidance performance. Movement ratings recorded during both CS and intershock intervals in pretraining were found to be good predictors of subsequent avoidance performance in preshocked Ss. Results are interpreted in terms of response repertoire changes produced by shock in conjunction with the defense reaction necessary in acquiring the avoidance response. (22 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)     

Response initiation and directionality as factors influencing avoidance performance.

Conducted 3 experiments with a total of 234 male Holtzman rats. Results indicate that permitting Ss to run in either of 2 directions to avoid shock (any-way training) resulted in performance superior to that of 1-way or 2-way avoidance. In the any-way condition, Ss often selected a bidirectional mode of responding. Exposure to signaled inescapable shock enhanced avoidance in all avoidance modes. Any-way training enhanced subsequent 2-way avoidance to a greater extent than did 1-way training. Results are interpreted in terms of the need to learn directional responses in avoidance training, role of response initiation in modifying avoidance behavior, and the effectiveness of running responses in determining avoidance performance. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cholinergic mechanisms and alterations in behavioral suppression as factors producing time-dependent changes in avoidance performance.

Studied 360 male hooded and Holtzman rats that received either one-way or shuttle-avoidance training at 1 of 4 retention intervals following exposure to signaled inescapable shock. Hooded rats exhibited a -shaped retention function in both tasks, while Holtzman rats demonstrated a curvilinear function only in the shuttle task. In Exp. II scopolamine improved and physostigmine disrupted shuttle-avoidance performance, and both altered the form of the retention curve in 300 male Holtzman rats. In the 1-way task physostigmine essentially produced a curve which approximates a -shaped retention function early in training. The data support a hypothesis based on activity changes, subserved by adrenergic-cholinergic mechanisms, as being involved in the production of the Kamin effect. (42 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of unconditioned stimulus escape and avoidance in discriminative avoidance learning in the gerbil (Meriones unguiculatus).

Gave separate groups of male gerbils (N = 80) shuttle-avoidance training or classical trials (CS and UCS pairings) in a 100-trial session. The shock UCS was either escapable or inescapable (i.e., of fixed duration-.1-3.0 sec). CRs, intertrial interval responses, and observations of the Ss' reactions to each UCS were recorded. Avoidance learning emerged only in groups exposed to escapable shock or a brief inescapable shock. Based on both the observational data of the nature of the shock-elicited reactions and shuttle performance, it is concluded that response termination of the UCS is not necessary for shuttle-avoidance learning. Results are discussed in terms of a punishment theory of avoidance and the species-specific defense-reaction hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

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)     

One-way avoidance behavior and septal lesions in the rat.

Compared 73 male Holtzman rats with septal lesions with 36 sham-operated and 41 unoperated controls on the acquisition of a 1-way avoidance response under several different stimulus and procedural conditions. Ss with septal damage were deficient in acquiring the avoidance response under several 1-way avoidance conditions involving an auditory CS, could not be distinguished from the controls in 2 experiments not involving auditory cues, and were superior to them in both a 2-way avoidance task and a conflictful 1-way avoidance task. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Kamin effect as a function of number of prior unsignaled inescapable shocks.

3 groups of 30 naive male albino Sprague-Dawley rats received 1, 5, or 10 unsignaled inescapable shocks either .02, 2.5, 4, 10, or 24 hrs prior to 1-way avoidance training. For each phase an additional 6 Ss were assigned to a no-shock control group. Trials to criterion in avoidance learning were a nonmonotonic function of time since prior inescapable shock; poorest performance was shown at intermediate shock-acquisition intervals. The locus of maximum performance decrement shifted to longer intervals with increasing numbers of prior inescapable shocks. Also, variability in performance increased, then decreased, as a function of time since inescapable shock in a manner parallel to the changes in performance means. Findings indicate that unsignaled inescapable shock is sufficient to produce Kaminlike effects. (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)     

Contrast effects in escape conditioning of rats.

In Exp I 39 male Holtzman albino rats ran for 20 trials from an alley where they received .2-, .4-, or .8-ma shocks to a goal box where there was no shock. All Ss were then shifted to .4 ma in the alley for 20 trials. Results show that rapid adjustment of running speeds occurred with shifts in amount of escapable shock. More importantly, however, positive and negative contrast occurred. In Exp I an experimental group (n = 10) received .2 ma on half of the trials and .4 ma on the other half, and 2 control groups (n = 10) received either .4 or .2 ma on all trials. Results show that the experimental group escaped faster on .4-ma trials than the .4-ma control group (positive contrast) and escaped more slowly on .2-ma trials than the .2-ma control (negative contrast). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of hippocampal granule-cell agenesis on acquisition of escape from fear and one-way active-avoidance responses.

Irradiated the head region of the hippocampus with low-level X ray in infant rats. This reduced the total number of hippocampal granule-cells by an average of 84%. 4 experiments were then conducted to extend the behavioral similarities previously noted between such hippocampal granule-cell agenesis and conventional hippocampal lesions. Irradiated Ss (n = 38) and nonirradiated controls (n = 74) were alike in the acquisition of a 1-way avoidance response, although there was a trend of greater resistance to extinction in the irradiated group. The irradiated group displayed facilitated acquisition of an escape-from-fear response. When 1-way avoidance was preceded by inescapable shock, the irradiated group was superior, suggesting that granule-cell loss, like hippocampal ablation, disrupts a tendency to remain immobile in the presence of stimuli related to inescapable punishment. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age differences in the control of acquired fear by tone.

Administered 10 inescapable shocks to 38 male Holtzman infant and adult albino rats in the presence of a 450-cps tone (CS) while Ss were confined in 1 compartment of a double-compartment shuttle box. Each S subsequently received 20 4-min trials (without shocks) in which a 230-, 450-, or 1000-cps tone, or no-tone, was made contingent upon S's presence in the former shock (fear) compartment. 8 Ss served as controls. Time spent avoiding the fear compartment during the various tone conditions revealed a steeper group gradient for pups than for adults, although mean avoidance of the CS condition was comparable for both groups. Individual stimulus generalization gradients were observed in 8 of 10 infants and 2 of 10 adults. Data are discussed in relation to the nature of maturational experience. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects on avoidance performance of vagal stimulation during previous fear conditioning in rats.

Attempted to determine, from experiments on 5 groups of 10 male albino rats each, whether parasympathetic stimulation given coincidentally with electric shock in a fear-conditioning situation would alter later performance on an avoidance conditioning task. 10 Ss were implanted with a small chronic electrode around the cervical vagus. During preconditioning, consisting of 8 trials of tone followed by inescapable shock, 1 group of Ss received stimulation of the vagus at the time foot shock was delivered. During subsequent avoidance conditioning, these Ss performed the avoidance task significantly better than Ss that received the same preconditioning without vagal stimulation and as well as Ss that had received no preconditioning shock trials. (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)     

Functional organization of the rat amygdala with respect to avoidance behavior.

Conducted tests with approximately 100 adult female albino Holtzman Sprague-Dawley rats. Bilateral electrolytic lesions in the periamygdaloid piriform cortex of Ss produced marked disruptive effects on the acquisition of active avoidance responses in a 1-way as well as a 2-way test situation, significantly impaired passive avoidance behavior, and inhibited feeding in a novel environment. Lesions in each of the 6 major subdivisions of the amygdala (cortical, medial, central, intercalated, lateral, and basolateral nuclei) consistently produced facilitatory effects on active avoidance behavior in 1-way as well as 2-way situations. Passive avoidance behavior was impaired in Ss with lesions in the central, intercalated, and basolateral nuclei. Damage to the anterior amygdaloid area or the nuclei of the lateral olfactory tract did not reliably affect active or passive avoidance behavior. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of avoidance behavior in rats following differential or nondifferential Pavlovian training along dimensions of the conditioned stimulus.

Assigned 36 male albino Holtzman rats, following 2-way avoidance training with an auditory CS, to 1 of 6 Pavlovian manipulations: discrimination or equivalence training along frequency or intensity dimensions, nominal single stimulus training, or unsignalled shocks only. Subsequently, Ss received separate generalization tests when frequency and/or intensity were varied. Intradimensional discrimination training tended to steepen generalization gradient and resulted in a peak shift away from the negative CS (safety signal) within the frequency continuum. Pseudodiscrimination equivalence training typically reduced stimulus control, even when training and test stimuli were not along the same dimension. These modifications of avoidance generalization gradients through interpolated noncontingent training provide additional evidence of the transfer of Pavlovian control to instrumental behavior. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of shuttle avoidance in young and adult rats.

Investigated stimulus generalization of 2-way active avoidance behavior in young and adult rats. In Exp. I with 12 adult and 12 young male Holtzman albino rats, CS frequency gained marked and comparable control over responding in both age groups; variation of background frequency prior to a no-tone CS, however, failed to exert any substantial control over avoidance behavior in either age group. In Exp. II with 12 Ss, Pavlovian frequency discrimination training was interpolated between acquisition of the shuttle response and generalization testing. Relative to their respective single stimulus control groups, the adult Ss showed a reliable peak shift in modal responding and the young Ss revealed a distortion in the gradient at frequency values on the side of CS+, opposite that of CS-. Although the occurrence of a peak shift was somewhat surprising in light of the fact that CS- here served as a "safety" signal, the data are interpreted as consistent with explanations of discrimination learning based upon the summation of excitatory and inhibitory gradients. In general, both experiments suggest that variations of CS frequency in an active avoidance situation tends to result in similar gradients for both young and adult Ss. The disparity between the present and previous findings are discussed in terms of the response requirements of the test situation. (French summary) (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pavlovian extinction in rats during avoidance response prevention.

Attempted to determine whether extinction of the aversive properties of a CS occurs during avoidance response prevention. 48 naive male albino Sprague-Dawley rats served as Ss. The CS remained somewhat aversive even after 5 5-min unreinforced presentations during response prevention, but it was significantly less aversive for Ss exposed to it without reinforcement than for nonblocked Ss or for blocked Ss given unreinforced exposures to the shock compartment in the absence of a CS. This finding supports analyses which assign a contributory role to Pavlovian extinction of CS aversiveness in facilitating avoidance extinction by response prevention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exposure to uncontrollable stress alters withdrawal from morphine.

Examined the influence of the controllability/uncontrollability of shock as a stressor on the severity of subsequent morphine withdrawal in 2 experiments with 84 male Holtzman rats. In Exp I (36 Ss), Ss that received 2 daily sessions of 80 yoked-inescapable shocks, in contrast to those given 80 escapable shocks or restrained without shock, showed an enhanced series of correlated withdrawal behaviors (i.e., mouthing, teeth chattering, head/body shakes) 24 hrs later when injected with morphine sulfate (5 mg/kg) followed by a naloxone HCl (5 mg/kg) challenge. In Exp II (48 Ss), this finding was replicated with escape-yoked-restrained Ss given saline injections during the pretreatment phase, but the impact that inescapable shock had on later precipitated withdrawal was completely blocked when Ss were administered naltrexone HCl (14 mg/kg) before each shock session. Findings are discussed in terms of the capability of inescapable shock to activate an endogenous opiate system, thereby leading to a sensitization of release or receptor processes that could protentiate later morphine withdrawal. (56 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)