Age differences in retention as a function of learning.

The hypothesis that observed age-related decrements in recall scores derive primarily from degree of acquisition rather than from retention deficits per se was investigated. 40 elderly and 30 young Ss learned 9 paired associates under equal learning opportunity, learning to criterion or overlearning conditions. Retention was measured at 20 min. and 1 wk. Elderly Ss learned less on equal exposure and required more trials to criterion, but once having learned the material retained it as well as young Ss. Trials beyond criterion did not enhance the retention scores of elderly Ss and may have introduced negative motivational factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Loss of depth avoidance in chicks as a function of early environmental influences.

Established a relationship between imprinting and visual cliff performance, 2 areas not previously associated with one another. 16 hybrid chicks reared sequentially in 2 distinctively different environments showed clear preference for their earlier rearing environment when tested upon a visual cliff, even when such a preference ran counter to depth avoidance, a response which is known to be strong and visually determined in chicks. The relationship of these findings to environmental imprinting is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal function in avoidance learning and punishment.

Discusses the effects of hippocampal lesions in avoidance and punishment situations. It is proposed that animals with such lesions cannot process information about places and therefore cannot employ place strategies in avoidance learning and punishment situations; they can only employ cue strategies that involve learning to approach or avoid a cue or to perform a response in the presence of a cue. Intact animals, on the other hand, can employ both place and cue strategies. The data are, to a large extent, consistent with this hypothesis. Implications for theories of learning in situations involving aversive reinforcers are discussed. (125 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned drinking as avoidance learning.

Conducted 4 experiments with a total of 104 male Sprague-Dawley albino rats. Blocking the robust conditioned drinking response following conditioning eliminated the isotonic procaine conditioned response (CR) but not the hypertonic procaine CR. Ss allowed to drink in the box during conditioning formed a larger CR than Ss merely injected with hypertonic or isotonic procaine who were prevented from drinking in the box: response blocking during extinction eliminated the latter CR. The CR to hypertonic procaine could also be eliminated if no experience of drinking water in the box occurred either during baseline or during conditioning. Blocking the drinking response, like blocking shock avoidance, markedly reduced its high resistance to extinction. Results suggest that rats overdrink to avoid anticipated illness, and fail to extinguish partially because they are never exposed to the fact that no illness will occur even if no drinking occurs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensory responsiveness and avoidance learning in rats.

Conducted an analysis of sensory responsiveness and avoidance learning in 3 experiments using 5 rat strains: MNR/Har/Lu, MR/Har/Lu, RCA/Lu, RHA/Lu, and RLA/Lu. Ss totaled 470. There were significant differences among the strains in response to electric footshock. Also, the strain-specific shock intensity as the UCS elicited significantly higher rates of avoidance learning as compared with the rates of avoidance learning under an equal but average level of shock intensity as the UCS. In general, discrete auditory and visual sensory modes as the CS produced almost the same rate of avoidance learning. The proportion of variation in avoidance learning attributable to strains was significant under all 6 experimental conditions except the no-discrete CS and strain-specific UCS conditions. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cage size as a factor in environmental enrichment.

Investigated the effects of cage size and cage surface texture as factors in environmental enrichment. 79 C57BL/6J mice were reared in 1 of 4 types of cages: small wire, small Plexiglas, large wire, or large Plexiglas. Dependent measures included gross body weight at 38 and 50 days of age, open-field activity and defecation, running-wheel activity, exploration, and water consumption. Cage size significantly affected 38-day gross body weight, open-field activity and defecation, and water consumption. These findings indicate that cage size is an important factor in the enriched environment experience, and they are in accordance with data reported previously by the authors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term retention of vocabulary after keyword and context learning.

Long-term retention of new vocabulary meanings acquired through keyword or semantic-context methods was assessed in two experiments. College students learned a list of 30 English vocabulary-meaning pairs until all meanings could be correctly recalled when they were given the vocabulary words. Subjects were again tested on cued-recall performance 1 week later. Although the keyword method facilitated initial learning of the vocabulary meanings, there were no differences in long-term retention as a function of learning method. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spared retention of inhibitory avoidance learning after posttraining amygdala lesions.

Previous findings indicate that the memory-impairing effects of posttraining amygdala lesions are attenuated by increasing the number of training trials given prior to the induction of the lesion. The aim of this experiment was to determine whether the degree of impairment is also influenced by the footshock intensity used during training. Rats were given 1 trial of inhibitory avoidance (IA) training with either no footshock or a footshock at 1 of 3 intensities. Sham or neurotoxic amygdala lesions were induced 1 week later. On a retention test performed 4 days after surgery, the performance of all amygdala-lesioned rats given footshock training, including those given the lowest training footshock, was better than that of amygdala-lesioned rats given no training footshock. These findings of preserved retention of IA learning in rats given posttraining amygdala lesions do not support a general hypothesis that the amygdala is a locus of permanent changes underlying aversively motivated learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction of avoidance in rats as a function of duration and number of blocked trials.

Gave 15 groups of 8 Sprague-Dawley rats each avoidance training in a runway. Each S was then blocked in the presence of the CS for either 1, 5, or 12 trials, each lasting for either 0, 5, 10, 50, or 120 sec. Results indicate that the greater the number of blocked trials and the greater the length of each blocked trial, the less the resistance to extinction. The key variable in determing the resistance to extinction was total blocking time as opposed to either the number of blocked trials or length of each blocked trial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of adrenocorticotropic hormone on conditioned avoidance in rats interpreted as state-dependent learning.

140 male Charles River CD rats were given 1 training trial that was followed 2 days later by 1 test trial in a "step-out" passive avoidance task. Each S was injected with either ACTH or placebo before training and before testing. 4 groups of Ss were used, representing the 4 possible training-testing injection combinations: placebo-placebo, placebo-ACTH, ACTH-placebo, and ACTH-ACTH. ACTH given in testing increased avoidance for subjects that had received ACTH in training and decreased avoidance for those that had received placebo in training. (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)     

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)     

Relatively brief environmental enrichment aids recovery of learning capacity and alters brain measures after postweaning brain lesions in rats.

Two experiments showed that enriched postlesion experience aided in overcoming effects of simultaneous bilateral cerebral lesions made at 30 days of age in 64 male inbred Fischer rats (Exp I) and 60 male Berkeley S-sub-1 rats (Exp II). The lesions were directed to the occipital cortex, but in most cases there was also some impairment of the hippocampus. For 60 days after operations, half of the Ss lived in small individual cages and half lived in groups in large enriched-environment cages. They were then pretrained and tested on the standard 12 Hebb-Williams problems. Daily injections of methamphetamine (vs saline) during the period of differential experience in Exp I had no effect on the behavioral scores. Exp II included groups that received only 2 hrs/day of enriched experience, and they benefited as much as groups that remained in the enriched environment 24 hrs/day. Results demonstrate significant beneficial effects of environment when bilateral lesions were made at a later age and when the periods of enriched experience were shorter than have previously been tested. Two additional experiments with 112 Berkeley S-sub-1 rats revealed significant effects of both lesions and environment on weight and RNA/DNA of brain regions. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of avoidance dispositions by social learning.

In line with the experiments on social learning in animals by imitation, this experiment sought to determine whether rats could learn to respond to the non-behavioral cues of other rats. The "cue" was to hear the squeal of another rat in a painful (shock) situation. When the squeal of the rat was paired with shocking the S a CR could be elicited; not so without shock. Rats also responded differentially to the cue whether in a black or white alley, or whether they were or were not permitted to escape. From Psyc Abstracts 36:04:4EK12M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term retention of the habituation of lick suppression in rats.

Conducted 5 experiments with a total of 97 naive male albino Holtzman rats. Retention of habituation of suppression of licking to the presentation of 2-sec pure tones was measured 7, 21, and 42 days after an initial series of habituation-training sessions (10 trials/day for 4 days). No recovery was found after 7 or 21 days, and there was only slight recovery after 42 days. No group approached its initial level of responsiveness. Habituation produced by a single, 2-sec stimulus was retained for at least 30 days. Recovery did occur with changes in the frequency of the auditory stimulus or the modality of stimulus. Habituation was insensitive to changes in the test environment other than the test stimulus itself. Habituation transferred from the behavioral context associated with nondrinking to that associated with drinking. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central catecholamine and peripheral noradrenaline depletion by 6-hydroxydopamine and active avoidance learning in rats.

Reports 3 experiments on the relationship between catecholamine (CA) depletion, plasma corticosterone (11-OHCS) levels, and active aversive learning in 108 male Wistar rats. A baseline study showed no significant relation between resting levels of 11-OHCS and central and/or peripheral CA depletion. On a 2-way avoidance learning task, depletion of brain CAs produced a widespread learning deficit. When both central and peripheral CAs were depleted, only escape learning emerged. Similar effects occurred on a 1-way task, but differences were not so marked. The findings are discussed in terms of a theory of CA-dependent cues. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste aversion learning in young and adult rats.

Compared a total of 159 male Long-Evans rat pups and adults on their ability to learn taste aversions with 1- and 2-bottle tests, 2 different illness-inducing agents and flavors, and varying taste–illness delays. Rat pups learned taste aversions with either 1- or 2-bottle tests, but only with short taste–illness delays. Delays of 60 min were sufficient to block taste aversion learning in pups. Pups also failed to demonstrate neophobia to a novel taste. These findings suggest that pups forget taste information more rapidly than adults, perhaps because taste information is not so salient for pups as for adults. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term retention of the classically conditioned eyeblink response in rats.

Retention of the classically conditioned eyeblink response in rats was tested with a conditioned stimulus (CS)-alone extinction test and 2 sessions of reacquisition training. Retention of the eyeblink conditioned response (CR) during both tests was highest 24 hrs and 1 mo after initial acquisition. Three months after initial acquisition, responding during the CS-alone test was at baseline, but there was significant savings during reacquisition. By 6 mo after initial acquisition, the memory for the eyeblink CR was not expressed in either test. The group differences in retention, despite initial acquisition of the eyeblink CR to equal levels, suggest that rat eyeblink conditioning may provide a useful behavioral model for studying the neural processes underlying memory retention and loss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of a spatial discrimination by rats as a function of age.

144 female albino Sprague-Dawley rats, equally divided among 3 levels of food deprivation, were given 10 trials/day on a spatial discrimination until 1 errorless day occurred. 1/2 of the Ss were 33 days old (juveniles) when training began; the other Ss were between 100 and 120 days old (adults). Results show that juveniles learned more slowly than adults, and Ss given a smaller daily food ration learned in fewer trials. The age-related difference in learning rate was interpreted to be a consequence of relatively ineffective inhibitory processes among the juveniles in view of the associated differences in sequence of choices and other behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction of environmental enrichment and genotype.

Assessed the effects of exposure to an enriched environment, from birth-38 days of age, using 3 behavioral tests: open field, exploration, and running wheels. 144 inbred mice from 3 strains (A/J, C3H/HeJ, and C57BL/10J) were used as Ss in a 3 * 2 * 2 factorial design: 3 strains, enriched and control treatment, and males and females. Significant main effects due to strain, treatment, and trials were found in open-field activity, exploration, and running-wheel activity. Main effects due to strain and trials were found in open-field defecation. Genotype interacted with treatment on 3 of the 5 dependent measures and interacted with trials on all measures. Coefficients of genetic determination for the various dependent measures were between .08 and .43. Results support the hypothesis that environmental enrichment increased activity and decreased exploration. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)