Maze Problem Research Articles

Effects of time and experience on hippocampal neurochemistry after damage to the CA3 subfield

Bilateral injections of kainic acid into the hippocampal CA3 subfield destroyed the CA 3 pyramidal cells and produced a behavioral impairment, an inability to solve spatial maze problems. The behavior recovered, however, with daily experience in a maze task, and the rate of recovery was accelerated by additional daily experience. This recovery of function could be the result of compensatory changes in the distribution or function of the various hippocampal pathways. In the present experiment, this possibility was investigated neurochemically. Five putative neurotransmitters or their synthetic enzymes were measured in dissected regions of the hippocampal formation. Both the long-term effects of the lesions and the effects of behavioral training were determined. A number of alterations in hippocampal neurochemical systems were detected. Acute changes due to the lesions included a widespread loss of glutamate, and regionally specific decreases in glutamic acid decarboxylase (GAD) activity and cholecystokinin (CCK) and norepinephrine (NE) concentrations. Long-term changes included a decline in choline acetyltransferase (ChAT) activity throughout the hippocampal formation, and increases in NE in certain regions. Behavioral testing prevented the decline of ChAT activity, and increased the concentrations of GAD and CCK. The neurochemical conditions present at the time when trained rats recovered behavioral function may indicate the crucial conditions for the occurrence of the behavior.

Nerve growth factor produces a temporary facilitation of recovery from entorhinal cortex lesions

Mature rats with entorhinal cortex lesions are impaired on learning a series of complex maze problems. A single, bilateral injection of NGF into the dorsal hippocampus caused an improvement during the initial maze learning, but it did not result in permanent recovery from the effects of the brain lesions. It is possible that chronic administration of NGF may have conferred more long-lasting functional recovery.

Memory and septo-hippocampal connections in rats.

Operated control rats and rats with small lesions in the medial septal region were tested for postoperative retention and transfer learning in a pulse-shaped elevated maze. Both maze problems were, in an empirical sense, spatial. Only when the rats worked on an alteration problem with start box reversals between sessions could the performance be characterized as depending on working memory. It was the working-memory conditions that sustained lesion-induced impairment on the tests of retention and transfer learning, and the lesion-induced behavioral impairment did not ameliorate during the four additional training sessions. Performance on problems that could be solved by reference-memory mechanisms was not impaired by the lesions. The small, but effective, lesions in the medial septal region were presumed to have severed a substantial number of connections comprising the major anterior input from the septum to the hippocampus but to have left intact much of the anterior hippocampal efferents. It is concluded that spatial cognitive mapping is crucially dependent on a basis capability for working memory which, in turn, depends on circuitry involving connections from septal region to hippocampus.

Effects of prenatal treatment with methylazoxymethanol acetate on growth, development, reproductive performance, learning ability and behavior in the rat offspring.

Jcl:SD rats were treated intraperitoneally with methylazoxy-methanol acetate (MAM acetate) at 0, 5 and 20 mg/kg dosage levels on day 14 of gestation, and were allowed to deliver spontaneously. Their offspring were examined for learning ability in a water T-maze at 10 weeks of age. Examinations of postnatal growth, development, reproductive performance, morphological alterations of the brain and other aspects of behavior were also carried out. The offspring of mothers that received 20 mg/kg of MAM acetate showed a slight decrease (less than 10%) of body weights from birth through adulthood, and slight decreases (2-22%) of liver, kidney, spleen and testis weights at 3 weeks of age as compared to the controls. They also showed slight delays in ear pinna separation, lower incisor eruption, eye and vaginal opening, but had normal appearances and reproductive performance. On the other hand, the cerebrum weights of the offspring in the 20 mg/kg group were approximately 50% less than controls. Microscopically, the micrencephalic offspring showed greatly reduced cerebral hemispheres and abnormal cortical cytoarchitecture. No significant differences were noted between the offspring of the 5 mg/kg of MAM acetate group and the control offspring. In an open-field behavioral tests, the offspring in the 20mg/kg group showed a decrease in the latent period and increases in the number of sections crossed and rearings. Their spontaneous night activity measured by a wheel cage increased as compared with controls. In the triple T-maze, the micrencephalic offspring made 1.4-2.8 times as many errors as controls did throughout trial days. There were no statistically significant differences in the behavioral parameters between the offspring in the 5mg/kg group and the control offspring. However, 2 animals in the 5 mg/kg group did not solve the maze problem within 10 minutes of the observation period while all controls successfully escaped from the maze.

The effect of early visual experience on spatial maze learning in rats.

In the 1st of 2 experiments on spatial ability, groups of sighted and blind, light-reared (LR) and dark-reared (DR) rats were tested on a series of (Hebb-Williams) maze problems and their reversals under appetitive and aversive reinforcement conditions. Significant effects due to early rearing conditions, vision at time of testing, and problem were found. Dark-reared rats learned the problems whose solution depended on nonvisual cues more slowly than LR animals. Blindness at time of testing had a significantly adverse effect on the performance of LR and DR rats on all problems, but a significantly greater effect in the DR animals. In a 2nd experiment DR rats were also found to perform less effectively than LR rats on a 17-arm radial maze throughout a 36-day period during which variations in the task were introduced. The results reveal the impact of early visual experience on the development of the ability to acquire spatial concepts.

Brain biochemistry and learning ability of rats treated with propoxur given in diets of varying protein content

The influence of propoxur on several biochemical brain parameters of 3-week-old Wistar male rats was tested. The substance was administered for 30 and 50 days at a 9000-ppm concentration in a low-protein diet (4.5% casein—LPD) and in a normoprotein diet (26% casein—NPD). The results of the Hebb-Williams test rating the learning ability of the rats were also analyzed. LPD depressed acetylcholinesterase (AChE) activity in the serum and brain as well as the activity of aromatic amino acid aminotransferases (AAA) in the brain. The brain serotonin (SE), noradrenaline (NA), and protein levels were also lowered. Addition of propoxur depressed still more the enzymatic activities and the NA and protein levels, whereas it increased the SE level. Propoxur given with NPD diminished AChE activity in the brain and serum and AAA activity in the brain, but its effect was less pronounced than when it was included in LPD. The SE, NA, and protein levels then remained unchanged. Rats fed LPD gave poorer results in the Hebb-Williams test than those receiving NPD. Addition of propoxur to LPD did not change the results of this test. On the other hand, rats fed propoxur in a NPD made a greater number of mistakes in solving maze problems of increasing degree of difficulty.

Maze training alters brain weights and cortical RNA/DNA ratios

In order to test whether training leads to anatomical and chemical changes in the brain, individual rats were given self-paced trials in mazes, traversing the maze in order to get from a food station to a water station. In 30 days of this training, during which they had no social interaction, the rats developed significant increases in weight and RNA/DNA of standard samples of cerebral cortex, as compared with littermate rats in either of two control conditions: (a) rats confined to small individual cages ( N = 70 per condition); (b) rats that traversed the empty maze box with no maze barriers present ( N = 29 per condition). Whereas the rats who faced maze problems decreased average transit times through the maze on successive trials, the rats that traversed the empty box showed no regular trend in running times over trials. The cerebral effects of maze experience versus control conditions were similar in pattern but were smaller in magnitude than effects of experience in a social group in a multisensory complex environment. This clear evidence of cerebral changes as consequences of maze training adds further support to the indications that similar cerebral changes resulting from enriched experience are due to learning rather than to other factors. The changes that follow training or enriched experience can be linked with other evidence concerning the roles of RNA and of protein synthesis in the formation of long-term memory traces. The U.S. Government's right to retain a nonexclusive royalty-free license in and to the copyright covering this paper, for governmental purposes, is acknowledged.

Opponent choices of below average performers

The present paper examined the preferences of below average performers for opponents. In Experiment 1, subjects solved maze problems and were subsequently given feedback indicating they had below average ability. They were then asked to indicate their preferences for above average, average, or below average others as opponents for a subsequent competitive interaction. Results indicated that below average subjects preferred below average and average persons equally as opponents. Supplementary data suggested that below average subjects may be assuming that they will improve on later trials and thus be able to succeed against average-ability opponents. Experiment 2 offered further evidence in support of this notion. The results suggest that the similarity hypothesis may not apply to those cases where it is in the individual’ s self interest to believe he will improve. The implications of the results for competition and social comparison are discussed

Effects of combined entorhinal cortex-hippocampal lesions on locomotor behavior, spontaneous alternation and spatial maze learning in the rat

Male Sprague-Dawley rats with combined lesions to the dorsal and lateral aspects of the entorhinal cortex in one hemisphere and of the contralateral dorsolateral hippocampal formation were compared with both operated and unoperated controls on three different behaviors, monitored across a 53 day postoperative period. The rats with the combined entorhinal cortex-hippocampal lesions (EH) showed transient hyperactivity in the open field, transient reduction in spontaneous alternation levels in an unbaited T-maze and persistent deficits in learning spatial maze problems. The results of the present experiment are discussed in comparison with those from experiments on rats with bilateral hippocampal lesions and those from experiments on rats with bilateral entorhinal cortex lesions. Although some similarities among these findings suggest that these two brain regions probably function in a coordinated fashion with respect to these behaviors, differences in the various syndromes are also discussed.

Dorsal but not ventral lesions of the caudate nucleus disrupt maze learning in the rat

Learning of a series of Hebb-Williams maze problems was investigated in rats with bilateral lesions of the anterior caudate nucleus. Rats with lesions restricted to the dorsal aspect of the anterior caudate nucleus were significantly more impaired than those with lesions restricted to the ventral aspect of the anterior caudate nucleus. Maze learning performance did not differ significantly between rats with lesions of the ventral caudate nucleus and sham-operated animals. The findings were interpreted as further evidence of the particular importance of the anterodorsal caudate nucleus in the processes of learning and remembering.

Neurologic sequelae of experimental febrile convulsions.

A study was designed to investigate the effects of experimentally produced hyperthermic seizures on the brain of the developing rat. Severty-nine newborn Sprague-Dawley white rats were divided into five groups and exposed to one of the following: Nonseizure-producing hyperthermia at 5 or 15 days (febrile controls), seizure-producing hyperthermia at 5 or 15 days, or no hyperthermia (afebrile controls). As the animals matured, seven developmental reflexes were tested and there were no differences found among the five groups in the ages at which these reflexes were acquired. At age 3 1/2 months, the ability of rats to adapt to a maze, and later to solve 12 maze problems, was studied. Although there was no significant difference in the amount of time required for any of the groups to adapt to the maze, there was a significant difference in the number of maze errors made by the different groups of rats. The mean error score for the control group was 118.5, compared with 183.0 (p less than 0.001), for rats with seizures at 5 days and 161.4 (p less than 0.001), for rats which convulsed at 15 days. It is apparent that experimental induction of a single hyperthermic seizure in the young rat interferes significantly with the animal's maze-solving ability at a later age.

The behavioral effects of prenatal hypoxia in the rat

Pregnant rats were exposed to an oxygen depleted atmosphere (13% oxygen in nitrogen) at normal pressure in 2-hr daily sessions extending over approximately the last 14 days of pregnancy. Their progeny were compared with control progeny in terms of age of eye-opening, open-field behavior, and Hebb-Williams maze problem solving ability. The groups were not distinguishable by their performance in the open-field, but the experimental animals opened their eyes significantly earlier and made significantly more errors on Hebb-Williams maze problems.

D-Amphetamine: Disruptive effects on the long-term store of memory and proactive facilitatory effects on learning in inbred mice

Male, C57BL/6J mice were given two daily trials on an appetitively-motivated successive brightness discrimination maze problem; they then received daily intraperitoneal injections of saline or d-amphetamine for 5 days. When trained again in the maze, mice in all d-amphetamine groups tended to display impaired retention: retention was significantly impaired in the 2.0 mg/kg group. Naive mice were treated exactly as were the pretrained mice except that they received no initial maze training prior to drug treatments. Mice in all naive d-amphetamine groups tended to display enhanced acquisition of the maze problem: acquisition was significantly enhanced in the 1.0 mg/kg group. These results could not be explained as effects of d-amphetamine on attentional, motivational or other performance factors.

An Analysis of the Visual Latent Learning in Rats

MOTOYOSHI and MITANI (3) have reported that exploratory experience on the transparent glass floor above the enclosed-maze was effective on the solution of the maze problem. In their experiment, rats were given successively 12 maze problems (the modified HEBB-WILLIAMS Intelligence Test) on the glass floor for 6 successive days, looking down into the each maze for 4 minutes per day, and 9 days after, rats were tested within each maze. The purpose of the present study was to examine the result of their experiment under slightly different conditions.RABINOVITCH-ROSVOLD Intelligence Test for Rats (6) was used as the apparatus throughout the present experiments. All the barriers (blocks), including the tops of them, were painted black to contrast with the painted white floor and the white fixed walls surrounding the field. Two sheets of transparent glass were used, the one covering the maze and the other the second floor above the maze (Fig. 1). Eighteen albino rats, aged 10 weeks at the beginning of handling, were used as SS. After adaptation to the enclosed-field without barriers and RABINOVITCH-ROSVOLD'S Practice Problems A, B, and C (Fig. 2), SS were divided into two groups. E-Group (Experimental) : The barriers were introduced into the enclosedfield. SS were landed on the glass floor above the maze (No. 4 Test Problem as shown in Fig. 2), and permitted free exploration for 10 minutes per day for 5 consecutive days. C-Group (Control) : Free exploration trials were procedually identical to E-Group except that all the barriers were removed from the enclosedfield. On the next day, testing was conducted. All SS were given 5 trials in the maze (No. 4 Test Problem), and the number of errors committed was recorded. The results are shown in Fig. 3 and Table 1. There is no significant difference between two groups. It seems to be concluded that the visual latent learning was not demonstrated in this experiment. In MOTOYOSHI and MITANI' s study, however, a kind of cumulative effect by giving 12 problems successively may result in statistically significant difference between two groups. To see whether there is the cumulative effect or not, 5 problems (No. 5, 9, 2, 10, and 4 Test Problems) were used in this experiment. Ten rats were used for E-Group, .and 8rats for C-Group. After giving exploratory experience on the glass floor above the enclosed-field (barriers constracted for E-Group and no barriers for C-Group) for 10 minutes twice, S was run in the maze for testing. Three days after, this procedure was replicated using the next problem, and so on. From the results shown in Fig. 4, 5, Table 2, and 3, it is unreasonable to assume that there are any cumulative effects in maze performance. Next experiment III was designed to ascertain whether the effect of exploratory experience on maze performance is increased by giving attention to the maze. To turn the rat's attention to the maze pattern, two naive rats were put into the maze when S was permitted free exploration on the glass floor. For C-Group there were no barriers in the enclosedfield, but for E-Group barriers were introduced, i. e., No. 3 and No. 6 Problems (Fig. 2). Testings were conducted on each problem. The results are presented in Fig. 4, 5, Table 4 and 5. With a single exception (the first trial on No. 6 Problem), there are no significant difference between two groups.To sum up, neither “visual latent learning” nor “cumulative effect” was demonstrated in the present study. But that the variances of the error scores of E-Group are quite smaller than C-Groups' (Table 2-5) might suggest the possibility that E-Group rats had learned something about the maze.

Strychnine and suppression of exploration.

Abstract In Experiment I, rats under the influence of strychnine were given 20 trials on a very simple Hebb-Williams maze problem and six days later were given a further 20 trials on the same problem when they were not under the influence of the drug. On the drug day, the experimental animals made fewer errors than the control animals, but on the retention test without the drug, the difference was not upheld. These results were taken to mean that strychnine can suppress exploration in maze tasks. This was supported in Experiment II. Maze adapted rats were given an exploratory test which allowed them to take either a familiar route or a number of alternate routes to the goal. Animals injected with strychnine took the familiar route while control animals explored the maze.

Effects of posttrial electrical stimulation of hippocampus and caudate nucleus on maze learning in the rat

Abstract Ten rats with bilateral, monopolar electrodes in hippocampus or caudate nucleus received electrical stimulation (ES) following massed or spaced training trials on a number of maze problems. Animals receiving hippocampal ES after spaced trials showed significantly better retention than comparably trained caudate stimulated or normal controls. Under massed trials only the rats receiving hippocampal ES showed significant disruption of learning. Threshold voltage required for response, and sequence of observed behavior were quantitatively and qualitatively different for hippocampus and caudate nucleus. Hypotheses proposing shifts in motivational level or aversiveness of ES could not satisfactorily explain the results. The data suggest that memory trace consolidation can be facilitated or disrupted by postrial ES.

Isolated rearing and Hebb-Williams maze performance.

48 male hooded rats were reared from weaning to adulthood either individually in small opaque-walled cages or together in larger, open cages containing various objects. Following rearing, Ss' “emotionality” and their efficiency at solving maze problems were measured. Consonant with other studies, Ss reared in isolation were more “emotional.” Unlike previous reports, Ss of the isolated rearing condition were as efficient at solving maze problems as Ss of the “enrichment” condition. It is concluded that the problem-solving efficiency of the two groups was equalized by reducing the effects of the emotionality by harsh deprivation for the incentive, by greater pretraining habituation, and by reducing the possibility for direct positive transfer from the training of enrichment to maze solving.

Short-term amnestic effects of electroconvulsive shock in a one-trial maze learning paradigm

This study investigated the effects of ECS on the retention of open-field maze problems in which positive reinforcement was employed. After extensive pre-training, rats were exposed to a series of novel maze problems. Experimental animals received ECS (a) immediately after a single trial (b) 60 sec after trial 1 and (c) immediately after trial 2. The retest performance of convulsed animals was inferior to that of controls only when ECS was administered immediately after trial 1; even then considerable savings were obtained. The results show that only short-term amnestic effects of ECS are obtained with highly trained animals running for positive reinforcement in an open field maze.

Effect of Toxocara canis infection on the ability of white rats to solve maze problems

Rats were orally infected with 5,000, 7,500, 20,000, and 33,000 infective Toxocara canis eggs. Paired controls were similarly treated except that the eggs were omitted from the inoculum. The ability of rats infected with 20- or 33,000 eggs to solve complex maze problems during the second week of infection was significantly reduced. Retesting of these rats during the fourth week revealed the persistence of a learning deficit, although percent reduction in total errors was equal to the control value. Other rats were tested on complex maze situations prior to infection with 20,000 eggs. The performance of these rats on retesting during the second week of infection was similar to that of controls. The migration patterns of these larvae in rats was found to be similar to that reported for mice; invasion of the brain commenced during the latter half of Week 1. The cerebral cortex and cerebellum were found to harbor the majority of larvae present in the brain.

Effects of bilateral lesions in the hippocampus on acquisition of two maze problems

Rats with hippocampal lesions and operated control rats were tested in an open field and trained on an alley maze and on an elevated maze (multiple-Ts). Deficits on both mazes occurred in the lesioned Ss with no significant difference between experimental and control groups in wall-following tendencies. Enhanced thigmotaxis cannot account for the deleterious effects of hippocampal lesions on maze learning. The lesions were relatively small (25%) and did not invade the thalamus.