Maze-learning Ability Research Articles

Basal forebrain infusion of HC-3 in rats: Maze learning deficits and neuropathology

Ten adult male Sprague-Dawley rats were infused with hemicholinium (HC-3) using mini-osmotic pumps over a 14 day period through bilateral, chronically implanted cannulae in the nucleus basalis magnocellularis (nbm). Ten matched controls were infused in the same fashion with saline. HC-3 rats receiving implants demonstrated a significant deficit in maze-learning ability compared with individual and group performances before receiving the implants. In saline rats there was no significant difference in maze-learning ability before and after receiving implants. The HC-3 group receiving implants demonstrated a significant deficit in maze-learning ability compared with the saline control group. Serial sections through nbm from control and HC-3 rats indicated that all cannulae were located within infusion range of nbm. In HC-3 subjects, cholinergic cell bodies were destroyed with concurrent degeneration of terminal fields in cortex. Except for cannula insertion damage, the cholinergic neurotransmitter system appeared unharmed in controls. Stains for neuritic plaques and neurofibrillary damage were negative in both groups. The memory deficit in experimental subjects supported by the demonstrated destruction of nbm cholinergic neurons suggests that HC-3 may be useful in the development of an animal model for Alzheimer's Disease.

The development of water maze-learning ability in rats. (2) Effect of pretraining with the water-filled straight channel

To determine whether pretraining with the water-filled straight channel affects learning acquisition, we studied the water filled multiple T-maze learning ability in 8-weeks-old SPF Wistar-Imamichi rats. The performance time for the straight channel was markedly shortened at the 2nd and 3rd trial compared to the time at the 1st trial on the 1st day. But at subsequent trials on days 2 and 3 it was longer than at the 3rd trial on day 1. At the 1st trial on day 1, the performance time of the group unexperienced in the straight channel was more than three times that of the experienced group. In subsequent trials, however, both groups showed similar performance times. More errors were observed in the unexperienced group than in the experienced group at the 1st trial on day 1. No difference was found between the two groups in subsequent trials. These results indicate that the learning acquisition was largely influenced by pretraining in the straight channel at the 1st trial on day 1.

The effects of handling at different ages on the subsequent learning ability of 2-year-old horses

Forty weanling Quarter Horses, from the Pitchfork Ranch, Dickens, Texas, were randomly assigned to one of five groups based on the amount of handling they would receive. The five groups were: (1) limited handling; (2) 1 week of handling; (3) 2 weeks of handling; (4) 3 weeks of handling; (5) continuous handling for 18 months. As 2-year-olds, the horses were tested in a simple place-learning T-maze after being preconditioned. A maximum of 30 daily trials were conducted for 20 consecutive days, with feed location alternating between sides on successive days. If a horse met the criterion of 11 out of 12 correct responses with 8 correct responses being consecutive, it was retired without completing the 30 trials. Group 1 made fewer correct responses during the 20 days than any other group except Group 3. All groups achieved learning by Day 10, but the most-handled group reached a consistently higher percentage of correct responses earlier than the less-handled groups. Group 5, the group receiving the most handling, was the least emotional, as determined by the animals' reactivity to a novel stimulus, and received the highest scores for trainability after being ridden. Preconditioning trainability scores, or estimates of the horses' ability to learn prior to conditioning and testing, tended to predict maze-learning ability. These scores were also significantly correlated with post-maze training scores.

The influence of persistent crowding on the age changes of behavioral parameters and survival characteristics of rats

One hundred fifty-six male Sprague-Dawley rats were submitted to crowding (12 rats/Makrolon ®-IV cage) from an age of 5 months onwards. An equal number from the same age cohort served as a control (6 rats/Makrolon ®-IV cage). As part of an age-test program, behavioral parameters (spontaneous motor activity, reactive motor activity and maze-learning ability) were measured at various ages between 8 and 30 months. The rats were sacrificed for additional measurements after the behavioral tests. Survival curves and age-specific mortality rates were calculated for those rats which died spontaneously in the course of the study. Control rats showed a significant decrease in spontaneous motor activity after an age of 18 months. Reactive motor activity of the controls revealed a fall in the number of large movements between 9 and 15 months, whereas the number of small movements increased up to an age of 30 months. Crowding conditions increased significantly both spontaneous and reactive activity. Maze-learning ability declined significantly with age in the controls whereas crowded rats revealed a tendency to better performance which seemed to be submitted to a seasonal rhythm. Crowded rats showed an improved survival characteristic, beginning at an age of 700 days. Mortality curves turned out to be distinct and parallel by straight line regression. It has been concluded that the positive effects of crowding on behavioral parameters and survival could be attributed to a decrease in vulnerability rather than to a lowered rate of aging.

Behavioural teratology: post-natal consequences of drug exposure in utero.

The effects of pre-natal exposure to drugs that subsequently affect the post-natal behaviour without apparently causing noticeable brain damage forms the subject of behavioural teratology. This review summarizes the experimental studies of several investigators who showed that pre-natal administration of such psychotropic drugs as meprobamate, isocarboxazid and reserpine reduced the maze-learning ability of the mature offspring. A more detailed survey of the effects of D-amphetamine and diazepam is then given. Both drugs were not foetotoxic and only caused appreciable changes in locomotor activity of the offspring at least 14 days after birth. With the amphetamine treated rats, these changes were biphasic (elevated at 15 days and reduced at 21 days) whereas the diazepam treated animals showed a reduction in locomotor activity for at least 21 days after birth. The results of our own studies, and those of others, do not enable a correlation to be made between the effects of the various drugs on the development of specific central neurotransmitters and the behavioural deficits noticed. The review concludes with an outline proposal for screening drugs for their potential as behavioural teratogens. The possible mechanisms whereby behavioural teratogens may cause subtle changes in the maturation of the brain are also outlined.

Gender and early environmental influences on activity, overresponsiveness, and exploration.

One hundred eighty-five rats reared in either an enriched or restricted environment were tested during adulthood to determine the influence of gender and rearing environment on 3 related response characteristics, activity, overresponsiveness, and exploratory behavior. Eight experiments were performed. It was found that although females are more active than males, rearing environment does not influence behavior in the running wheel or open field. When tested in a complex compartmentalized open field, females in general and restricted rats are significantly more active than enriched males. In addition, over subsequent testing, restricted animals are increasingly responsive and fail to habituate to the testing stimuli. When tested and retested for maze learning ability, males excel over females; enriched rats maintain their ability to outperform restricted rats, although both groups had previously learned the problem. Moreover, enriched rats demonstrate a greater tendency to explore and make irrelevant section entries on a maze that is problem free. Restricted rats, specifically, and females generally, have difficulty suppressing a learned repetitious pattern of rewarded responding when it is subsequently punished; restricted rats were deficient in the ability to passively avoid or escape noxious stimuli. These experiments, as well as supporting evidence in the literature, indicate that rats reared in a restricted environment develop a limited behavioral repertoire which is characterized by a generalized tendency to overrespond, a propensity towards perseverating in repetitious patterns of limited and circumscribed responding, and a failure to habituate to repeated contact with novel stimuli.

Delayed maze-learning in rats after prenatal exposure to clorazepate.

Five pregnant Long-Evans rats were given 32 mg/kg of body weight of clorazepate dipotassium (Tranxene) intramuscularly on gestational days 8.5, 9.5, and 10.5. Five control mothers received sterile water. The control group of offspring (n = 19) and the experimental group (n = 20) were compared by means of a timetable for neurologic development and for maze learning ability. Although the experimental group was significantly slower in stomach-lifting and walking, the neurologic battery as a whole did not disclose any consistent difference. At 21 days of age, the experimental rats weighed significantly more than the control rats. On trials 10 to 14, the control group ran the maze in less than half of the time of the experimental group. The study emphasizes the need to include tests of cerebral function in addition to developmental reflexes to screen for subtle effects of teratogens, which the simpler developmental tests may miss.

The effect of ribonucleic acid injections upon the maze-learning ability of rats

Rats received intraventricular injections of whole brain ribonucleic acid (RNA) via a cannula over two consecutive days of training. Two tests were conducted 14 and 30 days later. Compared to saline controls, there was a significant treatment by test period interaction for errors. However, there was no reliable difference between groups in terms of errors or time. It is suggested that RNA injections do not reliably decrease the amount of time to complete a complex maze, but do produce an initial enhancement of performance in terms of errors.

Effects of hormone manipulations and exploration on sex differences in maze learning

The maze learning ability of male rats castrated at birth, males and females treated with cyproterone acetate or sesame oil, and females treated with testosterone within the first 10 days postpartum was compared to that of nonmanipulated males and females (Experiment 1). Neonatal castration and injections of cyproterone acetate and testosterone were found to significantly reverse normal sex differences in maze learning. In Experiment 2, differences in gonadal hormone secretions and activities during adulthood on maze learning ability were assessed. It was found that gonadectomy did not significantly influence the performance of males and females. In Experiment 3, females were found to exhibit a greater tendency to explore and make irrelevant section entries on a maze that was problem free. It is suggested that differences in maze learning are more greatly influenced by brain sex than by subsequent gonadal hormone secretions during adulthood and are also due to the tendency of females to make more exploration-linked errors.

The relationship of gestational age to vitamin A induced postnatal dysfunction.

In an effort to determine the relationship between time of administration and consequent behavioral effects on progeny, a uniform subteratogenic dose of vitamin A (80,000 I.U./KG) was administered to gravid Sprague-Dawley rats during one of five periods of gestation (days 5-7, 8-10, 11-13, 14-16 and 17-19). Offspring were examined for changes in rate of weight gain, locomotor activity and maze learning ability (T-maze with return to nest as reward and multiple T water maze escape). Vitamin A 8-10 animals were hyperactive, vitamin A 11-13 animals acquired T-maze slower than controls and both vitamin A 8-10 and 11-13 acquired water maze slower than controls. Vitamin A 11-13 animals were significnatly lighter than controls and all other vitamin A groups.

Maze-learning ability of Drosophila melanogaster (reply)

Maze-learning ability of Drosophila melanogaster (reply)

Genetic and environmental correlations between brain weight and maze learning in inbred strains of mice and their F1 hybrids.

The relationships among body weight, cerebellum weight, cerebrum weight, maze-learning ability in a double T-maze, and discrimination learning in a Y-maze were studied in six inbred strains of mice and some of their F1 hybrids. The subjects were 131 male albino mice from 14 genotypic groups: five inbred groups and nine groups of crossbred offspring. Intra- and intergroup correlations were computed between all possible pairs of the anatomical and behavioral traits. A significant difference between the intragroup and intergroup correlations for any pair of variables was taken to indicate the presence of a genetic correlation between the two variables. On this basis, positive genetic correlations were indicated between T-maze learning ability and Y-maze learning ability, between body weight and T-maze learning ability, and possibility between body weight and both cerebellum and cerebrum weight and between cerebrum weight and T-maze learning ability. Negative genetic correlations were indicated between cerebellum weight and running time in both mazes and between total number of successes in the Y-maze and Y-maze running time.

Strain differences in maze-learning ability of Drosophila melanogaster

IF it could be demonstrated that Drosophila are able to learn, then our extensive knowledge of the genetics of this dipteran could be applied to understanding the biological bases of learning. Reports of learning in Drosophila1–3 sometimes involve changes in orientation as the result of aversive stimulation, for example, electric shock. The use of these stimuli can bring additional problems such as conditioned inhibition where the animals cease responding altogether4. The present paper is the first report of work on a unique learning situation which is based on the well-known mazes used to study taxes in Drosophila5 and involves no aversive stimulation.

Effects of experimentally induced hyperlysinemia on maze learning in mice

The experiment was designed to test effects of experimentally induced hyperlysinemia on maze learning ability in the mouse. Six% L-lysine was placed in the drinking water during gestation, and/or during nursing and/or during postweaning in a factorial combination. The young were tested at 40 days of age in a water-escape T maze. A week later all animals were retested for retention. Findings revealed that overloads of lysine resulted in temporary impairment, but permanent impairment occurred only if excess lysine was administered during gestation. Biochemical analysis revealed a sharp decrease in urea nitrogen in the urine, and a blood ammonia and lysine increase.

An analysis of single-gene effects on avoidance, maze, wheel running, and exploratory behavior in the mouse

Thirty-one different single-gene mouse mutants on the inbred C57BL/6J background were tested for their wheel-running behavior, exploratory activity, active avoidance, and maze learning. The effects of 27 coat-color alleles and of four other mutations were assessed by comparing the performance of mutant mice to that of their siblings (heterozygous or normal) and to that of a group of normal C57BL/6J mice. Twelve mutants exhibited wheel-running or exploratory activity levels different from that of normal mice. Similarly, seven mutants were found to attain an avoidance performance level significantly higher than that evident in control mice. Two of the high-avoiding mutants were also characterized by higher maze learning ability. The results point out that though these behavioral traits are influenced by genes at many loci, a single gene may substantially contribute to the additive and dominance genetic variance of the behavior.

The labyrinth method of comparing wild and domestic rats: Origins of animal psychology revisited

Ten wild and 10 domesticated rats were run in a 4-alley Lashley maze with food as a reward. Domesticated rats learned the maze in fewer trials and less time, but did not make significantly fewer errors. Domesticated animals were judged more active both by an index of activity and by observation. It was concluded, contrary to popular belief, that domesticated rats need not be considered degenerate in their maze-learning ability and that their propensity for exploratory behavior is suggestive as one reason for their faster maze learning.

The effects of deprivation of rapid eye movement (REM) sleep on maze learning and aggression in the Albino rat

To determine the effects of deprivation of rapid eye movement (REM) sleep on the behavior and maze learning ability of rats, 51 male albinos were trained in a T maze and each was assigned to one of four groups matched on learning ability. Three of the four groups were then placed on small water-surrounded platforms and subjected to one of the following conditions for 26 days: Groups SPE and SPC were confined to small platforms and thus deprived of REM sleep, while group LPC was positioned on larger platforms. The subjects in the fourth group were home cage controls. The platform animals were removed to their home cages for three hours each day where only the SPE animals were kept in a wakeful state. During the deprivation period, each of the animals were paired daily with a member of his own or another group in a neutral cage and rated for aggression. At the conclusion of the deprivation period, five animals from each group were sacrificed and the brain removed for pathological examination. The remaining animals were tested for retention and reversal in the T maze and then began an acquisition series in Lashley's Maze III. Results indicated that the animals maze learning ability was not consistently affected by the deprivation procedure and no neuropathology was observed. Deprivation resulted in a significant increase in aggressive behavior, however. It was hypothesized that the central nervous system of most animals is capable of tolerating prolonged REM sleep deprivation, carrying on during wakefulness those processes normally subserved by the REM phase.

The effect of pre-natal Cannabis sativa on maze learning ability in the rat.

Pregnant Wistar MW-3 derived rats were treated with 250 mg/kg suboutaneously of an extract of Cannabis Sativa in 2.5 ml/kg of polyethylene glycol 300 or 2.5 ml/kg of polyethylene glycol 300 alone. A third group was left untreated. Treatments were made on days 8–11 of pregnancy. At term, the offspring were delivered normally by the mothers.

Enhancement by ethanol of visually evoked responses in the goldfish optic tectum

Flash-evoked potentials and multiple unit discharge were recorded from the superficial layers of the goldfish optic tectum, and post-flash histograms were prepared. When goldfish were intoxicated by a level of ethyl alcohol just sufficient to depress maze-learning ability, the first of three components of these evoked responses was consistently enhanced. These results indicate that ethanol can unbalance neural processes near the periphery as well as central brain mechanisms. Furthermore, the data provide a basis for suggestion that the retina might be useful as a model system for further physiological and pharmacological analysis of the mechanisms by which ethanol disrupts normal brain functions.

Acetylcholinesterase from Tryon-maze-bright and Tryon-maze-dull rat strains is identical

A search was made for any qualitative difference between acetylcholinesterase from Tryon's rat strains reported to differ genotypically in maze-learning ability and brain acetylcholinesterase level. Results of inhibition experiments and heat denaturation showed that a structural difference is improbable. Thus the difference in activity levels should be due to the amount of enzyme per weight unit of brain tissue.