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The effects of the lurcher mutation on object localization, T-maze discrimination, and radial arm maze tasks.

The Lurcher mutation is characterized by degeneration of the cerebellar cortex and cerebellar ataxia. The mutants were compared to littermate controls of the same background strain in three spatial tasks: 1) left-right discrimination in a water-filled T-maze, a reference memory task requiring a win-stay strategy; 2) the radial arm maze, a working memory task requiring a win-shift strategy; 3) object localization, a reference memory task requiring the use of cognitive mapping. Lurcher mutants were impaired in the object localization and radial arm maze tasks but not in the left-right discrimination task. These results indicate that trial-independent tasks and reference memory tasks using cognitive mapping may be particularly vulnerable to cerebellar degeneration.

Animals↗

Cerebellar contribution to spatial event processing: Morris water maze and T-maze.

Recently, a cognitive function of cerebellar networks has been challenging the traditional view of the cerebellum as a motor control centre. Among the cognitive abilities reported to be affected by cerebellar deficits is the capacity to solve a spatial problem. We investigated the influence of a cerebellar lesion on spatial abilities by behavioural analysis of rats that had undergone surgical hemicerebellectomy (HCb; HCbed rats). Experiments were performed with a Morris water maze (MWM) and a water T-maze in both cue and place versions (visible or hidden platform respectively). Results indicate a severe impairment in coping with spatial information in all phases of MWM testing as well as in the T-maze paradigm. However, if the MWM cue phase was prolonged, HCbed rats displayed some ability to learn platform position, although at a level significantly different from controls. They succeeded in finding the platform, even in a pure place paradigm, such as finding a hidden platform with the starting points sequentially changed. Retention testing was also performed, demonstrating that HCb affects acquisition but not retention of spatial information. HCbed animals exhibit such disrupted exploration behaviour that they can display only peripheral circling, and they can acquire spatial relations only when proximal cues are available. Furthermore, in all phases of testing, platform finding for HCbed animals is essentially based on place strategies. Thus, a specific pattern of spatial behaviour, markedly different from that displayed following hippocampal or cortical lesions, characterizes cerebellar lesioned rats. These results are discussed taking into account the role in procedural learning recently assigned to cerebellar networks, demonstrating that the cerebellar circuits represent the keystone of the procedural components of spatial event processing.

Analysis of Variance↗

[The relearning time of rats in a radial maze elicited by the revolving alteration of extra-maze markers].

A new approach was applied to evaluation the errors in the course of learning of rats in 12-arm radial maze (RM). The number of repeated erroneous visits of the last six arms ("late errors") decreased only after a decrease in the number of repeated erroneous visits of the first six arms ("early errors"). This points to insufficiency of using the common index of the mean error for evaluating learning ability in the RM. Change in the character of errors in the operative and space memory was studied in the RM-conditioned rats after disruption of the relations between the intra- and extra-maze markers. This disruption was reached by rotation of the RM by 180 degrees after rat's visiting of 5 arms during its stay in the 6th one. It was found out that rats were able to recognize the changes in the extra-maze markers caused by the RM turn and to relearn within 4-5 days.

Adaptation, Physiological↗

Effects of diazepam on behavioural and antinociceptive responses to the elevated plus-maze in male mice depend upon treatment regimen and prior maze experience.

Recent studies have shown that brief exposure to an elevated plus-maze (EPM) produces non-opioid antinociception in male mice. The present experiments were designed to assess the effects of diazepam on this phenomenon. When acutely administered, low doses (0.5-1.0 mg/kg) of diazepam failed to produce an anxiolytic profile and exerted rather inconsistent effects on EPM-induced elevations in tail-flick latencies. In EPM-experienced mice, chronic treatment with higher doses of diazepam (2-4 mg/kg, 8 days) produced a weak anxiolytic action and inhibited the early phase of EPM antinociception only. However, in EPM-naive mice, 8-day diazepam pretreatment exerted a marked anxiolytic effect and completely eliminated the antinociceptive response to the maze. Together, these data support the view that anxiety is a key factor in certain forms of adaptive pain inhibition and suggest a possible mediational role for benzodiazepine receptors. Our findings also show that prior exposure to the EPM, rather than chronic handling/injection, greatly reduces the anti-anxiety effect of diazepam. Furthermore, since re-exposure to the maze, per se, decreased time spent on the open arms and central platform, a shift in behavioural baseline ("retest anxiogenesis") may have contributed to the weak behavioural effects of diazepam in test-experienced animals. Importantly, as chronic treatment with diazepam did not influence this anxiogenic-like retest profile, our data suggest that a single prior experience of the EPM may radically alter the nature of the anxiety reaction provoked by this test.

Analgesia↗

Effects of pre-exposure to the same or different pattern of extra-maze cues on subsequent extra-maze discrimination.

In two experiments, rats learned a spatial discrimination between maze arms defined by their relationship to a variety of extra-maze cues. Prior exposure to the actual arms between which animals were required to discriminate tended to retard subsequent learning (by comparison with a control group either given no pre-exposure to the extra-maze cues or exposed only to arms pointing in the opposite direction), whereas prior exposure to arms intermediate between those used in discrimination training tended to facilitate subsequent learning. These results are consistent with the suggestion that pre-exposure will facilitate discrimination learning when it reduces the associability of features or elements common to the stimuli between which animals are required to discriminate, more than it reduces the associability of the features or elements unique to each.

Animals↗

Previous maze experience required to increase open arms avoidance in rats submitted to the elevated plus-maze model of anxiety.

Studies have shown an increased open arm avoidance in rats re-exposed to the elevated plus-maze (EPM), which suggests a qualitative shift in emotional states from an unconditioned (Trial 1) to a learned (Trial 2) form of fear response, but a precise source of aversion has not been determined. Using rats submitted to the EPM or various EPM-derived configurations, this study was designed to investigate what previous maze experiences in Trial 1 are required to increase avoidance of open arms in EPM Trial 2. Results obtained from rats submitted to the EPM or EPM-derived configurations confirmed the increased open arms avoidance in Trial 2. Rats confined to either open or enclosed arms failed to show the increased avoidance of open arms in Trial 2. The results are discussed in terms of the minimum prerequisite in Trial 1 to elicit an avoidance learning response to open arms in Trial 2, and also the implications of an acquired fear response in rats for the study of the biological basis of anxiety.

Animals↗

Chronic opioids impair acquisition of both radial maze and Y-maze choice escape.

Chronic morphine impaired acquisition of two dissimilar behavioral tasks. In the radial maze, the performance of saline-treated and morphine-treated groups diverged with the latter failing to improve despite extensive training. In contrast, rats treated with naltrexone became skilled in the procedure 2-4 times as rapidly as saline controls. Withdrawal of treatment significantly improved performance of morphine-treated rats, with no change for rats treated with saline or naltrexone. When a second group of rats was extensively trained prior to instituting chronic morphine treatment, performance scores were not affected, suggesting that morphine does not impair spatial working memory despite subjective evidence of other gross behavioral effects, such as ataxia. In the Y-maze choice escape task, acquisition of a response strategy was significantly impaired in rats that had been previously treated with morphine for 17-21 days, despite clear indications that morphine-treated rats were sensitive to the aversive stimulus.

Animals↗

Spatial behavior in the Brazilian short-tailed opossum (Monodelphis domestica): comparison with the Norway rat (Rattus norvegicus) in the Morris water maze and radial arm maze.

The spatial behavior displayed in a swimming pool and radial arm maze by the Brazilian gray, short-tailed opossum (Monodelphis domestica) was compared with that of the laboratory rat (Rattus norvegicus). The performance of the opossums was clearly different from that of the rats in both tasks. The opossums failed to learn to find a hidden platform in the swimming pool (place task), but they did learn to swim to a visible platform. The opossums did learn working and reference memory components of the radial arm maze but showed different search strategies in this situation. The results are discussed with reference to possible species differences in motor behavior, ecology, brain structure and evolution.

Animals↗

[A method employing housing in a radial maze apparatus for estimating working memory in mice: effects of scopolamine and delay upon maze performance].

Male ddY mice were housed in a 4-, 6-, or 8-arm radial maze apparatus for 6 hr a day and then removed to a normal cage for fasting until the next day's trial. A water bottle was placed at the central platform. The end of each arm ran to the home cage through a guillotine door (G). Food was placed in the home cage. During the housing in the apparatus, one G was opened, and the remaining Gs were shut. The opened G was changed in random order during the housing period of 6 hr. At the beginning of the trial, all Gs were shut. The mouse was placed on the platform and was permitted to choose the arms until it chose all arms. When the mouse chose the last arm, the G was opened to allow stepping into the home cage. The mice housed in these apparatus learned to go to the home cage without entering already chosen arms within 4-6 days. Scopolamine (0.2 and 0.4 mg/kg, i.p.) impaired the maze performance. A 1- to 4-min delay impaired the performance slightly, but did not show any significant effect depending on the delay intervals. These results suggest that the apparatus is a useful and easy method for estimating working memory and the drug effects thereon in mice.

Animals↗

Lesions in the septo-hippocampal system or prelimbic cortex of rats do not alter the performance of a T-maze visual discrimination task but disrupt the performance of a T-maze alternation task.

Rats with lesions in the posterodorsal septum (SEP), prelimbic cortex (PRE), and control operations (CON) were tested in a continuous alternation task (intertrial interval, ITI = 0 s) and a visual discrimination task (ITI ca 100 s) in a T-maze. CON rats performed the alternation task significantly better than rats with SEP or PRE lesions. PRE rats, but not SEP rats, were able to master the task with continued practice. The three groups did not differ in performance of the visual discrimination task. These data suggest that the septo-hippocampal system and, to a lesser extent, the prelimbic cortex are specifically involved in the memory processes necessary for the performance of an alternation but not a visual discrimination task in a T-maze.

Animals↗

[Thrombocyte counts in TMB (Tryon Maze Brights) and TMD (Tryon Maze Dulls) rats following warfarin (author's transl)].

A dosage of 3 mg Warfarin/kg body weight causes a highly significant increase in the number of platelets both in TMB (Tryon maze brights) and TMD (Tryon maze dulls) rats. Different "intelligence levels" show no effect on this increase. In condition of rest the number of platelets is significantly higher in TMD rats than in TMB animals. With regard to a hypothetical relationship between the number of platelets and the amount of circulating and urinary catecholamines the results suggest a similar relationship in conditions of rest as can be shown in emotive (e+) and nonemotive (e--) Wistar rats as well as a varying reaction to stress -- different levels of "intelligence" and anxiety provided.

Animals↗

Impairment of water maze behaviour with ageing is counteracted by maze learning earlier in life but not by physical exercise, food restriction or housing conditions.

Spatial learning and memory decline with ageing in humans as well as rats. We examined the influence of different interventions on male Sprague Dawley rats with respect to learning ability and memory at the age of 5, 10 and 18 months. The intervention and control groups were: (RW) voluntary exercise in running wheels, (PW) sedentary, food restricted (by about 25%) to keep them at pair weight with RW, (S1) sedentary, fed ad libitum, (TM) forced training in a treadmill, and, (S4) sedentary, fed ad libitum. The animals in all groups were housed individually except those in group S4, which were housed four in each cage. The ability of learning and memory was determined in the Morris water maze. The results showed a significantly better learning ability when young in comparison with their ability when having grown older. At the age of 18 months, the performance was significantly better in the subgroups which had received training also at the age of 10 months compared to the subgroups receiving their first training. None of the various interventions had any significant effect on these functions. Repeated training seems to be the best intervention with respect to retaining learning ability and memory.

Aging↗

Of mice and mazes: similarities between mice and rats on dry land but not water mazes.

Mice are impaired relative to rats in place and matching-to-place learning when tests are given in a swimming pool. The rat advantage may stem from a superior spatial ability or from adaptation to a niche that has prepared them for competency in the water. In the present study, mice (C57BL/6) were compared with rats (Long-Evans) in a number of dry-land spatial tasks given on a radial arm maze and in a place task given in a swimming pool. The performance of the mice matched that of the rats in all dry-land tasks, but was inferior to that of the rats in the swimming pool. The results provide further evidence for a species difference in swimming-pool performance but do not support the idea that there are necessary differences in spatial abilities between mice and rats. It is suggested that, if optimal place learning is required for neurobehavioral studies of mice, such performance is more likely to be obtained in dry-land tasks than in swimming-pool tasks. Nevertheless, the species differences warrant further study because they could provide important insights into species differences is spatial learning more generally.

Animals↗

Place navigation in the Morris water maze under minimum and redundant extra-maze cue conditions.

Complex relational processes underlying place navigation learning were analyzed by minimizing the relational elements available to rats. The animals navigated in a standard water maze in darkness using controlled remote visual cues (back-lit shapes in opaque buckets aimed at the pool to keep the background dark) while being tracked by an infrared camera and computer. Learning was similar with 2 (AB) or 4 (ABCD) cues and as good as in a fully lit room with many cues (asymptotic escape time t = 5-7 s). The ABCD-trained rats were not impaired by removal of any 2 cues (t = 7). For AB-trained rats, adding 2 new cues (ABEF) or replacing AB with EF (EF) caused small (t = 11) or big disruptions (t = 20), respectively. By block 2, both groups (ABEF, EF) returned to asymptotic performance. But testing the ABEF rats on block 2 with only EF indicated that EF was learned (t = 12) but not as well as when only EF was present (t = 5). Thus transfer from a redundant to a minimal cue condition is immediate and easier than vice versa. Theoretical implications are discussed.

Association Learning↗

Human spatial navigation deficits after traumatic brain injury shown in the arena maze, a virtual Morris water maze.

OBJECTIVE: Survivors of traumatic brain injury (TBI) often have spatial navigation deficits. This study examined such deficits and conducted a detailed analysis of navigational behaviour in a virtual environment. DESIGN: TBI survivors were tested in a computer simulation of the Morris water maze task that required them to find and remember the location of an invisible platform that was always in the same location. A follow-up questionnaire assessed everyday spatial ability. METHOD: Fourteen survivors of moderate-to-severe TBI were compared to 12 non-injured participants. RESULTS: TBI survivors navigated to a visible platform but could not learn the location of the invisible platform. The difference between TBI survivors and uninjured participants was best indicated by two new dependent variables, path efficacy and spatial scores. CONCLUSION: This study confirms the capacity of virtual environments to reveal spatial navigation deficits after TBI and establishes the best way to identify such deficits.

Adult↗

Spatial memory activation of the parietal cortex measured with near-infrared spectroscopic imaging in the finger-maze of the Morris water maze analogue for humans.

To assess the cortical regions involved in learning spatial navigation, changes in oxyhemoglobin volume were measured with near-infrared spectroscopy in a task analogous to the Morris water maze. The blindfolded participants (Ps) were allowed to search the area inside the circular ring (20 cm) until they reached a goal (1 cm). The sitting and starting positions were randomly varied across trials, but the goal was in a fixed position so that the Ps could learn the allocentric spatial relationship between the goal and the experimental room. There was a significant sex difference (p < 0.05) in the present task, showing that performance in males was better than that in females. With this task, we measured brain activation in the first training trial, the probe test, and the motor-control trials. In the first trial, dorsolateral prefrontal and parietal cortices were activated. In the probe test, only the dorsolateral prefrontal regions were activated. These results suggest that the parietal cortex is critical for acquisition of spatial memory.

Adult↗