Developmental analysis of behavioral dysfunction in rats with septal lesions.

At 7 days of age, 48 male Long-Evans hooded rats received lesions of the septal nuclei or control operations. Ss then received 30 hrs of training on a DRL 20-sec schedule for 1 hr/day beginning at either 27 or 96 days of age. At 126 days of age, all Ss received 10 additional training sessions. After operant testing, all Ss received 10 additional training sessions. After operant testing, all Ss were tested on spontaneous alternation, spatial reversal, and passive avoidance. Results indicate that on a DRL 20-sec schedule Ss that received lesions of the septum neonatally and were tested at different ages performed in a similar manner. Approximately 50% of the Ss with lesions of the septal nuclei reached efficiency levels comparable with those of normal controls. When tested for retention, these efficient Ss still performed similarly to normal Ss. Ss with septal lesions were facilitated in the acquisition of a spatial habit, were deficient in spatial habit reversal, were less likely to demonstrate spontaneous alternation, and were deficient in passive avoidance. It is concluded that neonatal lesions of the septal nuclei produce permanent behavioral impairments on a diversity of measures and that, although juvenile animals with limbic system damage often manifest behaviors different from adult Ss, the difference is not evident during operant testing (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interactive effects of training condition and septal lesions on perseverative responding in the rat.

In a study with 30 male Wistar rats, Ss that had received septal lesions either prior to acquisition of a position habit (Group SAR) or immediately after position habit acquisition (Group SR) were tested on 2 reversals of the task. Compared with control-operated Ss, both groups of Ss with septal lesions exhibited position-habit reversal deficits. The 2 groups with septal lesions could not be distinguished in terms of the total number of errors made during reversal learning, but could be distinguished on the basis of the type of error committed. Compared with Group SR, Group SAR made significantly more perseverative errors on the 1st reversal and significantly fewer perseverative errors on the 2nd reversal. Group SR made significantly more nonperseverative errors than Group SAR on both reversals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed alternation learning under electrical (blocking) stimulation of the caudate nucleus in the cat.

Of 9 young adult cats with electrodes implanted in the dorsolateral caudate nucleus, 4 had previously reached criterion on a delayed alternation task. Tested under alternating conditions of stimulation and nonstimulation, these 4 Ss showed a significant performance decline with stimulation. When a marker was placed on 1 response panel, performance under stimulation did not decline. Stimulation did not affect the learning of a visual discrimination. The remaining 5 Ss were trained on delayed alternation with alternating stimulation and nonstimulation conditions. Under stimulation, performance remained near chance levels. These Ss were tested on position learning and reversal, and under unilateral stimulation. Results support the view that the caudate nucleus and prefrontal cortex mediate separate aspects of delayed response behavior. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective attention and response strategies as factors in serial reversal learning.

3 experiments investigated the basis of serial-reversal improvement in 40 white Carneaux pigeons. In the 1st, Ss trained on either color or position reversals alone performed more accurately than Ss initially trained on interspersed color and position reversals, and then shifted to 1 type of problem only. This suggests that the selective strengthening of attention to a single relevant dimension is 1 factor underlying rapid reversal learning. In 2 further experiments, Ss were trained on delayed conditional discriminations, the requirements of which were similar to those of a win-stay, lose-shift strategy. Ss' poor performance on these problems implies that such strategies do not play an important part in reversal learning in these Ss. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of context manipulation on memory and reversal learning in rats with hippocampal lesions.

Conducted 3 experiments with 83 male Long-Evans rats to investigate (a) the memory of hippocampus-damaged Ss, and (b) their ability to modify response strategies in relation to the influence of familiar contextual cues. In Exp I, groups of hippocampal and control Ss learned a simultaneous discrimination habit and were subsequently tested for its retention under variable contextual conditions. All groups recalled the discrimination response to an equally high level when testing conditions were constant throughout, but the hippocampal group showed impaired memory when contextual stimuli at recall testing did not conform to those of original learning. Results of Exp II indicate that the hippocampal impairment was not simply the result of introducing novel stimuli. In Exp III, Ss were administered a reversal learning task with contextual stimuli varied between the 2 tests. The typically observed impairment of hippocampal Ss on this task was reduced by contrasting contextual conditions. Results are seen to support a context-retrieval interpretation of hippocampal function. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhancement and retardation of discrimination learning in chicks after exposure to the discriminanda.

Used an imprinting procedure to expose groups of Ross domestic chicks (N = 57) to 1 or 2 moving objects on Days 1-5 after hatching for a total of 30 or 100 min. From Day 8-12 Ss were given a discrimination learning task. Ss exposed to 1 of the discriminanda learned the task in fewer trials than Ss exposed to neither. However, Ss that had been exposed to both stimuli took many more trials to reach criterion than Ss that had seen neither in the imprinting situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maturational loss of thermotaxis prevented by olfactory lesions in golden hamster pups (Mesocricetus auratus).

5 day-old golden hamster pups preoperatively were tested on a thermal gradient, subjected to bilateral or unilateral olfactory bulbectomy or control dorsal cortical removal, and then tested on Days 6–25. Locomotion and rectal or belly temperature were monitored throughout the 2-min test. Controls became quiescent in the hot end of the gradient on Days 5–7 but after Day 8 chose cooler regions and increased their activity. Both unilaterally and bilaterally bulbectomized Ss spent more time in the heat throughout testing, were less active, and allowed their temperature to rise more rapidly than controls. Percentage of time in the heat was elevated in all bulbectomized Ss although some retained the ability to make an olfactory discrimination. Enhanced thermal behavior is apparently not due to anosmia per se. Altered thermal perception or responsitivity may result from loss of "nonspecific" olfactory projections that normally would mature at the beginning of the 2nd week. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual differentiation of play behavior in the ferret.

Three experiments examined the endocrine mechanisms responsible for sex differences in prepubertal play behavior of ferrets. In Exp I, 6 gonadally intact adolescent males exhibited higher levels of "stand-over" behavior than 6 females did in tests between 63 and 123 days of age with gonadally intact female partners of the same age. In Exp II, with 69 Ss, those Ss exposed to androgen or to ovarian steroids over Days 5–20 of postnatal life subsequently exhibited significantly higher levels of stand-over behavior in tests with females than did control females gonadectomized on Day 5 and not given steroids. None of the Ss in Exp II exhibited levels of stand-over behavior comparable to those of the gonadally intact males in Exp I. In Exp III, with 36 Ss, males gonadectomized and implanted subcutaneously with testosterone capsules on Day 70 and tested with females at 84–96 days of age exhibited levels of stand-over behavior comparable to those observed in Exp I in gonadally intact males of the same age (Weeks 12–24). Males gonadectomized on Day 70 and given no hormone at testing exhibited significantly lower levels of this behavior. Significantly lower levels were also exhibited by males gonadectomized on Day 35 and females gonadectomized on Day 70, regardless of whether they were tested with testosterone present after Day 70. Sex differences in the expression of prepubertal play behavior of ferrets apparently result from differential exposure of males and females to androgen over an extended postnatal period. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two-step acquisition: Modification of an internal clock's criterion.

10 male albino Norway rats were trained on a discrete-trial peak procedure in which food, if available, occurred following the 1st response after a signal had been present for 10 sec. 10 other Ss were trained on the same procedure with a 20-sec criterion. When the time of reinforcement was reversed between groups, Ss adjusted their temporal criterion in 2 abrupt steps. During the intermediate state of the 3-step function, Ss used a temporal criterion that was near the geometric mean of the initial and terminal times of reinforcement. It is concluded that the intermediate transition state reflects an internal structure in the animal's information processing system not readily accounted for by stimulus–response models of behavior. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posterior extramarginal cortex and visual learning by cats.

Reports results of 3 experiments with a total of 59 mongrel and 11 Siamese cats. Extensive ablations of posterior cortex which spared the primary visual areas severely impaired visual pattern discrimination, detour learning, and spatial reversal performance. Lesions in the posterior ecto- and suprasylvian gyri (EP) produced significant deficits in learning multiple object discrimination problems, repeated reversals on spatial or visual cues, and successive visual discriminations. Ss with cortical ablations that did not invade the EP region but did cause damage to the optic radiations were not impaired in reversal learning and were deficient in successive discriminations only when tested with nonsalient cues. Thus, some of the defects shown by EP cats are qualitatively different from the losses in cats with damage to the geniculostriate system. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prenatal exposure to cocaine on conditional discrimination learning in adult rats.

Adult male rats that were gestationally exposed to cocaine and control offspring were trained on an instrumental conditioning task for assessment of the acquisition and reversal of an appetitive conditional discrimination based on olfactory cues. Offspring were derived from Sprague-Dawley dams that had received subcutaneous/ly (sc) injections of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on Gestational Days 8–20, pair-fed (PF) dams that were injected with saline, nutritional control dams (NC) that received saline injections, and nontreated control dams (LC). There were no differences among the prenatal treatment groups in acquisition of the barpress response or response rate throughout all phases of training. All prenatal treatment groups required approximately the same number of sessions to criterion on the initial odor discrimination. In contrast, adult C40 offspring required more sessions to acquire the reversal of the conditional discrimination than did animals from the other treatment groups (PF, NC, and LC). In addition, even at criterion performance for acquisition of the reversal discrimination, C40 animals exhibited lower accuracy on the 1st 10 responses and made significantly more errors before the 1st reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential ontogeny of working memory and reference memory in the rat.

Examined the ability of 15-, 21-, and 27-day-old rats to perform 2 spatial working memory problems (delayed alternation and discrete-trials delayed alternation) and a reference memory problem (position habit) in a T-maze. In the delayed alternation problem, each S was presented with a series of free-choice trials and was rewarded for regularly alternating responses to the left and right arms of the T-maze. In the discrete-trials delayed alternation problem, each S was forced to one maze arm and rewarded (forced run) and was then placed back into the start box and given a choice of arms (choice run). The direction of forced runs followed an irregular, counterbalanced series, and Ss were rewarded for choosing the alternate maze arm on choice runs. In the position habit problem, Ss were rewarded for consistently choosing 1 of the 2 arms of the T-maze. At all ages, rat pups learned to perform the delayed alternation and position habit problems. Only 21- and 27-day-old rats were able to learn the discrete-trials delayed alternation problem. Results of these experiments show that reference memory capacity is present by at least 15 days of age in the rat and does not develop further at later ages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Observational learning of quantity conservation and Piagetian generalization tasks.

20 1st graders who had scored 9 or less on a pretest of 8 Piagetian criterion tasks were divided into control and experimental groups. Experimental Ss underwent an observational learning phase in which a model correctly performed the 1st task used in the pretest, giving correct conservation judgments supported by justifications alternately based on identity, compensation, or reversibility considerations. All Ss were given the same 8 Piagetian tasks used in the pretest on immediate, 1-wk, and 3-mo delayed posttests. The experimental group generalized conservation to several tasks. One category of Ss behaved as rote learners and maintained conservation only for tasks closely similar to the modeled task and on immediate and 1-wk delayed posttest; a 2nd group of genuine conservers progressively generalized the conservation rule to more difficult tasks. The control group remained nonconserving throughout. Results are explained with reference to the Piagetian concept of sequential equilibration. The social experience of observation appeared to activate a cognitive restructuring of the Ss' mental operations. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response strength as a function of stimulus novelty: Concept formation in the pigeon.

Cites a previous study which showed that a distinctive CS presented on the 1st trial of acquisition generated more responses after extinction than another CS presented regularly during acquisition. In the present study 140 pigeons were presented with a different distinctive CS on each 1st trial of 5 acquisition sessions. Ss were then broken down into 7 groups which were tested, following extinction, for residual response strength of (a) Day 1 novel CS, (b) Day 2 novel CS, (c) Day 3 novel CS, (d) Day 4 novel CS, (e) Day 5 novel CS, (f) the regular CS, and (g) a novel CS never presented before. Contrary to the previous study where a novel CS inhibited responding, Group 7 exhibited the most responding in this study. Results support a concept formation interpretation of the previous study and are difficult to explain from a "stimulus trace" or "identical elements" position. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of hippocampal lesions and intertrial interval on single-alternation performance in the rat.

Trained 7 unoperated male Long-Evans hooded rats and 14 Ss with bilateral hippocampal or cortical lesions made by aspiration on a go, no-go task in which bar presses were reinforced on alternate trials. Performance was evaluated with both latency ratios (latency to 1st response on go trials/latency to 1st response on no-go trials) and response ratios (total responses on no-go trials/total responses on go trials). Ss were trained to criterion at successively increasing durations of ITI (10, 20, 40, and 80 sec.). While Ss with hippocampal lesions acquired the task more rapidly than controls with the initial 10-sec ITI, they were severely impaired when tested with the longer ITIs. (23 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of instructions and feedback on blood alcohol level discrimination training in nonalcoholic drinkers.

Investigated whether nonalcoholic drinkers can be trained to discriminate their blood alcohol levels (BAL) on the basis of internal cues. 72 male undergraduates classified as heavy drinkers came to the laboratory for 3 consecutive sessions, each consisting of 5 BAL estimation trials. The 2 manipulated independent variables factorially combined were beverage sequence and administration of BAL feedback. All Ss were told that they would receive mixed drinks containing vodka and tonic on each day, and all Ss received alcohol on Day 1. On Day 2, half of the Ss received alcohol and half received tonic alone; similarly, half of the Ss in each of these groups received either alcohol or tonic on Day 3. No S received BAL feedback on Day 1, and one-third of Ss did not receive feedback on Days 2 and 3. The remaining Ss received feedback on Day 2; half of the latter Ss also received feedback on Day 3, and half did not. Ss did not learn to discriminate their BAL on the basis of internal cues. Results are discussed in reference to the utility of BAL discrimination training in alcoholism prevention programs. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eye movements of monkeys during discrimination learning: Role of visual scanning.

In Exps I and II with 7 stumptailed monkeys (Macaca arctoides), Ss were given a series of 2-choice, dot-pattern discrimination reversal problems. Results indicate that the rate of reversal learning was markedly retarded by the experimental condition. The magnitude of the effect was unrelated to the similarity of the uninformative stimulus to the discriminative stimuli. In Exp III, 5 experienced Ss were given a series of discrimination problems without reversals, during half of which the experimental condition was in effect. The results were similar to those of the 1st 2 experiments. In Exp IV (3 experienced Ss), each trial began with uninformative stimuli, which were replaced by the discriminative stimuli when visual scanning occurred. The uninformative stimuli had no clear-cut effect on discrimination learning. Findings indicate that the information provided by above-minimum levels of scanning is not necessary for discrimination learning per se, but it does appear necessary for efficent discrimination learning. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prior exposure on conditioned taste aversion in the rat: Androgen- and estrogen-dependent events.

Studied the effects of preexposure and gonadal hormone manipulation on the extinction of a conditioned taste aversion in 198 male Sprague-Dawley rats. In Exp I, Ss were given 1 prior exposure to sucrose at some selected time (Days 4, 2, or 1) before a 2nd exposure (Day 0) to sucrose and a LiCl injection, or they were given only a single exposure (Day 0). Under single exposure, castrated Ss extinguished the aversion faster than either testosterone-treated castrated Ss or sham-operated Ss. In Exp II, estradiol, dihydrotestosterone, and testosterone were studied by using only a Day 1 preexposure condition. The testosterone-treated group maintained the aversion for the longest period, followed by dihydrotestosterone-treated, sham, castrated, and estradiol-treated groups. In Exp III, estradiol was administered alone or in combination with 2 doses of dihydrotestosterone. Findings indicate that the outcome of behavior was dependent on the ratio of estradiol to dihydrotestosterone, with variations in this ratio resulting in fast (estrogen effect) to slow (androgen effect) rates of extinction. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in spatial discrimination reversal learning between two inbred mouse strains following specific amygdaloid lesions.

Tested reversal learning for 2 groups of 85 male C57BL/6J and BALB/cJ mice following a bilateral lesion in either the basolateral, central, lateral, medial, or cortical nucleus of the amygdala. On the 2nd reversal, C57BL/6J Ss with a lesion in the lateral nucleus performed less well than intact controls and operated controls. The BALB/cJ Ss with a lesion in the cortical nucleus performed less well on the 1st reversal than these 2 control groups. Data indicate that effects of specific amygdaloid lesions on learning are not necessarily the same for all strains or stocks within a species, and that lesions simultaneously involving many nuclei may be of limited usefulness in understanding the relationship of the amygdala to reversal learning. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Irreversibility of imprinting after active versus passive exposure to the object.

64 isolated Peking ducklings were reared for 4 days with a hanging colored object (passive training). Half of the Ss also received 3 1-hr following sessions with the object (active training). Findings indicate that both groups chose the imprinting object in a simultaneous choice test administered on Day 5, but the preference of active-trained Ss was more robust than of passive-trained Ss. Each S was then reared with an object of a different color and shape. The preference for the 1st object was maintained in active-trained Ss, but not in passive-trained Ss. These results were also found when the objects were removed from the cages for 4 days. Findings suggest that preferences established during the sensitive period for imprinting can be eliminated (but not necessarily reversed) in Ss that are prevented from following the original object, but they are resistant to change in Ss given the following experience. A hypothesis is presented that emphasizes the importance of reafference and activation of brain stem pathways involved in following the formation of specific affiliative bonds. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)