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PubMed1989

[Deficits in radial-arm maze learning in aged rats].

The present study was designed to investigate the possible deficits in the place learning on the 8-arm radial maze in aged rats. In this task, reward was given in the 4 predetermined arms. Aged rats (27 months old, N = 7) acquired this task more slowly than young rats (12 months old, N = 11), and didn't reach to the performance level of the young rats within 80 training trials. Analysis of error choices revealed that the aged animals first entered in the unbaited arms more often than the young rats, whereas there was no difference in the number of re-entered choices to the baited and unbaited arms between the aged and young animals. Therefore, it was concluded that learning deficits in aged rats were attributed to deficits in the reference memory but not in the working memory.

Aging↗
PubMed1981

Can passive touch be better than active touch? A comparison of active and passive tactile maze learning.

In a comparison of the performance of active (n=15) and passive (n=15) mechanically yoked subjects who learned their way through a tactile maze, it was shown that active subjects mad more errors and took a greater number of trials to reach criterion than did passive subjects. In addition, the difference between active and passive performance was largely accounted for by the greater number of repeated errors made by active subjects. In a second experiment it was found that the poorer performance of active subjects could be attributed to the interfering effects of decisions about which way to move. However, the responsibility for the production of movement had no effect on performance. it was argued that the results reflected limits to the cognitive system, not the haptic system.

Adolescent↗
PubMed2003

Postnatal hypobaric hypoxia in rats impairs water maze learning and the morphology of neurones and macroglia in cortex and hippocampus.

Newborn rats were exposed to intermittent hypobaric hypoxia from birth until the age of 19 days. Spatial memory was tested in a Morris water maze from postnatal day (P) 23 to P32 and from P100 to P109. From P24 to P27 and on days P100 and P101, the escape latencies of hypoxic animals were longer than those of controls. At P24, the number of neuronal bodies increased in cortical layer II of the somatosensory, motor, and auditory areas, and in layer V of the motor area, but the number of neuronal bodies throughout the whole cortical thickness was unchanged. Decreases in the immunostaining density for neurofilaments (anti-NF 160), astrocytes (anti-GFAP), and oligodendrocytes (RIP) were found in the hippocampus, and the typical parallel organisation of neuronal and macroglial processes was lost. Decreases in immunostaining for neurofilaments and oligodendrocytes were also found in the somatosensory cortex and motor cortex. In adult hypoxic rats, at P114-P240, the number of neuronal bodies and the immunostaining density for neurofilaments, astrocytes, and oligodendrocytes in the examined areas were similar to adult controls; however, in the hippocampus we found hypertrophy of fine astrocytic processes and a decreased number of oligodendrocytic processes. We conclude that the neonatal brain damage induced by hypobaric hypoxia impairs spatial memory in infant as well as adult rats. Hypobaric hypoxia delays the maturation of neurones and substantially affects macroglia in the cortex and hippocampus.

Animals↗
PubMed2001

Neurobehavioural defects in adult mice neonatally exposed to nicotine: changes in nicotine-induced behaviour and maze learning performance.

Neonatal exposure to low doses of nicotine has been shown to disturb the development of low-affinity nicotinic binding sites in the cerebral cortex and to elicit a deviant behavioural response to nicotine in adult mice. In this study, 10-day-old male NMRI mice were exposed to one of three different doses of nicotine (3.3, 33, or 66 microg nicotine-base/kg body wt.) s.c. twice daily on 5 consecutive days to study dose-response effects of nicotine on adult spontaneous and nicotine-induced motor behaviour. The nicotine-induced behaviour test revealed a hypoactive response to nicotine in 4-month-old mice neonatally exposed to 33 or 66 microg nicotine-base, whereas the response to nicotine in control animals and mice exposed to 3.3 microg nicotine-base was an increased activity. Learning and memory functions were also investigated in adult animals neonatally exposed to 66 microg nicotine-base/kg body wt. in the same manner, in the Morris water maze and in the Radial arm maze. In the swim maze and the Radial arm maze tests, no significant differences were observed between nicotine-treated and control animals at the age of 4 months. At 7 months, however, a significant difference in performance was evident, indicating a time-response/time-dependent effect. Furthermore, it was shown that in mice exposed neonatally to a nicotine dose known to inhibit the development of the nicotinic low affinity-binding site (LA), the response to nicotine could not cause any increase in spontaneous motor activity as seen in controls.

Age Factors↗
PubMed1994

Spatial water maze learning using celestial cues by the meadow vole, Microtus pennsylvanicus.

The Morris water maze is widely used to evaluate to evaluate the spatial learning ability of rodents under laboratory settings. The present study demonstrates that reproductive male meadow voles, Microtus pennsylvanicus, are able to acquire and retain a spatial water maze task using celestial cues. Voles were able to acquire a modified outdoor Morris water maze task over 4 trials per day, whereby they had to learn and remember the location of a submerged hidden platform, using the position of the sun and associated celestial cues. Their proficiency on this task was related to the availability of the celestial cues, with voles displaying significantly poorer spatial navigation on overcast than clear days and when the testing time (and position of the sun and associated celestial cues) was shifted from morning to afternoon. These findings with meadow voles support the ecological relevance of the water maze task.

Animals↗
PubMed1991

Early postnatal hyperthyroidism alters hippocampal circuitry and improves radial-maze learning in adult mice.

Inbred mice show strain-specific differences in the hippocampal mossy fiber projection. These differences are most pronounced in the portion of the projection that forms synaptic connections with the basal dendrites of the CA3 pyramidal neurons [intra- and infrapyramidal mossy fiber (IIP-MF) projection]. We have previously demonstrated that the extent of the IIP-MF subfield is positively correlated with the capacity to perform a spatial radial-maze task and that an experimentally induced enlargement of the IIP-MFs, by means of postnatal thyroxine treatment, predicted the ability of adult two-way avoidance learning. In the present study, we tested whether this treatment would also influence radial-maze performance. Forty-five male mouse pups from the inbred strain DBA/2 (chosen because of scanty IIP-MF projection and poor radial-maze learning) were divided into three groups that received daily injections of either 2 micrograms L-thyroxine, an alkaline vehicle solution, or physiological saline. Treatment lasted from postnatal days 0 to 11. At the age of 3 months, these animals were tested in an eight-arm radial maze. The extent of their IIP-MF projections was measured by means of planimetry on Timm-stained sections. Thyroxine-treated animals made significantly fewer errors and had larger IIP-MF projections as compared to both control groups. Within each group, the individual variability of the IIP-MF projection was significantly and positively correlated with performance. We conclude that experimentally modified IIP-MF projections mediate processes underlying spatial working memory. It would appear that the hippocampal circuitry alterations induced by postnatal hyperthyroidism can counteract a hereditary lack of talent, albeit only partially and in selected populations.

Animals↗
PubMed1996

Both anteromedial and anteroventral thalamic lesions impair radial-maze learning in rats.

Disruption to the anterior thalamus (AT) may be an important factor in diencephalic amnesia. Rats with small lesions of the anteromedial (AM) or anteroventral (AV) nucleus showed persistent working-memory and reference-memory deficits in a 12-arm radial maze, although they were comparable to controls during the early part of training. The only activity difference in the maze was that lesioned rats failed to run more slowly when revisiting a baited arm. For all groups, both working and reference memory were impaired after extramaze cues were removed; removal of intramaze cues further impaired performance relative to the original conditions. These findings suggest the AT makes a distinct contribution to mnemonic functions, probably as part of an integrated system involving limbic cortex and the hippocampal formation, and that AT lesions produce a general rather than a specific deficit in spatial or working memory.

Animals↗
PubMed2005

Long-term enhancement of maze learning in mice via a generalized Mozart effect.

OBJECTIVES: An animal model of the 'generalized Mozart effect' (GME) - enhanced/normalized higher brain function in response to music exposure - has been established. We extend those results in two studies using another species (mice). Study 1: (1) maze testing after music exposure was extended to a minimum of 6 hours; (2) no exposure to music in utero. Study 2: (1) music exposure time further reduced; (2) maze testing extended to 24 hours. METHODS: Study 1: two mouse groups were exposed to music continuously for 10 hours per day for 10 weeks (Group I: Mozart's Sonata K.448, Group II: Beethoven's Fur Elise). After 10 weeks, the ability to negotiate a T-maze was assessed (recording working time in maze, number of errors). Maze ability was tested 6 hours following the last music exposure. Study 2: two mouse groups were exposed periodically to music (58% silence) 10 hours per day for 10 weeks. Experiments after 10 weeks examined the groups' abilities to run the maze (recording working time/errors). Experiments were conducted 24 hours following the last music exposure. RESULTS: The Mozart group exhibited significant enhancements compared with the control mice in both studies, i.e. significantly lower working time (p<0.05) and committed fewer errors. DISCUSSION: Observation of GME in another species supports its generality for the mammalian cortex. The absence of a GME in fMRI studies for the control music also indicates a neurophysiological basis. With extended exposure, GME is a long-term effect, indicating potential clinical importance. It has been demonstrated that GME reduces neuropathological spiking significantly in epileptics. We discuss the relevance of this study for epilepsy treatment.

Animals↗
PubMed1990

Hippocampal mossy fibers and radial-maze learning in the mouse: a correlation with spatial working memory but not with non-spatial reference memory.

One hundred and eight male mice from nine different inbred strains were tested for two aspects of learning in an eight-arm radial maze. In the first experimental arrangement of the maze, measuring spatial working memory, clear strain differences were found on the fifth day of training. Furthermore, this type of learning showed a high positive correlation with the size of the intra- and infrapyramidal hippocampal mossy fiber terminal field as revealed with Timm's staining. In the second experiment, in which non-spatial reference memory was tested, significant strain differences were found for the learning variables, but there were no significant covariations with the sizes of the intra- and infrapyramidal mossy fiber terminal fields. These results, combined with previous data, suggest that heritable variations of the hippocampal intra- and infrapyramidal mossy fiber projection influence processes determining spatial learning capabilities in mice.

Animals↗
PubMed2004

Prolonged initiation latency in Morris water maze learning in rats with ibotenic acid lesions to medial striatum: effects of systemic and intranigral muscimol administration.

The contribution of the rat striatonigral GABAergic system to spatial navigation was investigated in this study. We first tested the effects of ibotenic acid lesions of the striatum on place navigation performance in Morris water maze. Medial but not lateral striatal lesions produced a significant increase of escape latency, and this deficit was clarified as mainly caused by a marked increase of initiation latency rather than of thigmotaxis time (experiment 1). Next we tested the effects of systemic (0.5 mg/kg) and intranigral (2.0 ng/side) administrations of muscimol, a GABA receptor agonist, on the place navigation deficits produced by medial striatal lesions. Systemic muscimol administration significantly ameliorated the increase of initiation latency, while intranigral administration was not sufficiently effective (experiment 2). The results suggest that neural circuits containing medial striatal neurons play an essential role in place navigation performance probably through some movement preparation processes that precede movement execution, and the GABAergic system may be involved in this initiation process, although whether it is the striatonigral GABAergic system that is involved remains unclear.

Animals↗
PubMed2004

Water maze learning and forebrain mRNA expression of the neural cell adhesion molecule L1.

L1 and NCAM, two cell adhesion molecules of the immunoglobulin superfamily, have been implicated in the formation of neural circuits, synaptic plasticity, and cognitive function. In this study, we sought to investigate whether differences in the steady-state levels of L1 and NCAM expression in specific brain regions could account for individual differences in learning abilities. Using adult male Wistar rats, we evaluated mRNA levels of L1, NCAM, and the NCAM180 isoform in different brain regions (hippocampus, thalamus, striatum, prefrontal and frontal cortices) immediately after submitting rats to a massed training protocol in the water maze. The results showed that untrained and trained rats exhibited similar levels of mRNA for these molecules, which supports the view that training did not influence their immediate level of expression. However, in most of the brain regions we investigated (with the exception of prefrontal and frontal cortices), L1 mRNA levels were positively correlated with the latency to find the hidden platform in the water maze task and with posttraining plasma corticosterone levels. However, no correlations were observed for total NCAM or NCAM180 mRNA in the brain regions examined in this study. Given that animals with a slower spatial acquisition curve exhibited more anxiety-like responses, including thigmotactic behavior in the water maze and increased corticosterone levels, and that recent genetic studies indicate a role for L1 in anxiety, the current findings suggest a relationship among L1, anxiety, and cognitive processes.

Animals↗
PubMed1988

Maze-learning behavior in early adrenalectomized rats.

Rats adrenalectomized (ADX) on day 11 of life display enhanced brain growth due, at least in part, to a stimulation of cell proliferation and myelinogenesis. The present study investigated some functional consequences of this treatment. Rats were ADX or sham-operated (SHAM) on postnatal day 11 and then tested in adulthood for their problem-solving ability in a Hebb-Williams maze. The mean number of errors committed by ADX rats was lower than that of the SHAM controls on every test problem of the maze. ADX subjects also left the start box more quickly and ran the maze faster than the controls. When a subset of these same subjects was tested for running wheel activity, the ADX animals showed greater baseline running behavior and also learned more readily to respond to a fixed-interval schedule of reinforcement. The remaining animals were subjected to carcass analysis, which revealed that ADX rats under the food-restricted conditions necessary for maze testing had a lower percentage of body fat and a higher relative water content than SHAMs. Although there may be some relationship between enhanced maze-learning performance and altered activity or motivation in the ADX animals, the overall results suggest that the performance of these subjects reflects a real difference in learning ability. The neural mechanisms underlying this difference remain to be elucidated.

Adrenal Glands↗
PubMedDate not supplied

[An aversive olfactory signal during the Y-maze learning of mice selected for greater or lesser brain weight].

Learning abilities of mice selected by the small and large brain weights were studied in Y-maze. Thirsty mice were trained to find water in one of the maze arms. The minimal latency of this reaction reached in the process of learning was shorter in the mice selected by the heavy brain. Benzaldehyde which is commonly supposed to be an aversive olfactory stimulus being presented before drinking sharply increased the latency, nevertheless, it remained shorter in mice with heavy brain. The response to the aversive stimulus varied between the individuals, especially in mice selected by the small brain weight.

Animals↗