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At least 811 records · Page 45Linked to original sources
PubMed2001

Dead reckoning (path integration) requires the hippocampal formation: evidence from spontaneous exploration and spatial learning tasks in light (allothetic) and dark (idiothetic) tests.

Animals navigate using cues generated by their own movements (self-movement cues or idiothetic cues), as well as the cues they encounter in their environment (distal cues or allothetic cues). Animals use these cues to navigate in two different ways. When dead reckoning (deduced reckoning or path integration), they integrate self-movement cues over time to locate a present position or to return to a starting location. When piloting, they use allothetic cues as beacons, or they use the relational properties of allothetic cues to locate places in space. The neural structures involved in cue use and navigational strategies are still poorly understood, although considerable attention is directed toward the contributions of the hippocampal formation (hippocampus and associated pathways and structures, including the fimbria-fornix and the retrosplenial cortex). In the present study, using tests in allothetic and idiothetic paradigms, we present four lines of evidence to support the hypothesis that the hippocampal formation plays a central role in dead reckoning. (1) Control but not fimbria-fornix lesion rats can return to a novel refuge location in both light and dark (infrared) food carrying tasks. (2). Control but not fimbria-fornix lesion rats make periodic direct high velocity returns to a starting location in both light and dark exploratory tests. Control but not fimbria-fornix rats trained in the light to carry food from a fixed location to a refuge are able to maintain accurate outward and homebound trajectories when tested in the dark. (3). Control but not fimbria-fornix rats are able to correct an outward trajectory to a food source when the food source is moved when allothetic cues are present. These, tests of spontaneous exploration and foraging suggest a role for the hippocampal formation in dead reckoning.

Animals↗
PubMed2002

Effects of predictable and unpredictable intermittent noise on spatial learning in rats.

The effects of predictable (periodic) and unpredictable (aperiodic) intermittent noise of moderate intensity (68 dB) on the learning of a complex T-maze by genetically defined rats were investigated. In Experiment 1, three groups (n=8) of rats learned a multiple T-maze, one group under control conditions, one group with predictable intermittent noise and one group with unpredictable intermittent noise. Results showed a profound effect of noise on learning and behavioural scores. Noise-exposed animals made less errors, finished their trials sooner and explored less. There was no difference between predictable and unpredictable noise. Further tests, during which formerly noise-exposed groups learned a new route under control conditions (Experiment 2) or the former controls learned a new route with noise (Experiment 3), suggest that the effects of noise on learning were caused by an effect of noise on memory formation and/or retrieval, rather than by long-term shifts in behavioural strategies.

Analysis of Variance↗
PubMed1991

Clonidine reverses spatial learning deficits and reinstates theta frequencies in rats with partial fornix section.

Rats received knife-cuts to the dorsal fornix or sham-operations. Half of the animals from each group were injected with clonidine (0.01 mg/kg) and the others with saline before each daily trail of a 10-trial radial 8-arm maze task. The number of choices before the first repetition and the run time were used as performance indices. Lesioned rats were significantly impaired in the acquisition of this task. Clonidine-treated rats, lesioned or not, had an acquisition profile indistinguishable from that of sham-operated saline-injected rats, in spite of their increased run time. When tested one week after the last learning trial in a no-drug condition, lesioned rats treated with clonidine throughout learning maintained a high level of performance during the 5-day retraining phase. A parallel analysis of theta rhythms recorded in an independent group of rats placed in equivalent treatment and/or lesion conditions was then performed. Preoperatively, clonidine injections decreased theta frequency during both alert immobility and movement. Partial fornix lesions produced an increase in theta frequency. Finally, clonidine in fornix-damaged rats decreased theta frequency, thus reinstating the postoperative values at a level statistically no different from that recorded preoperatively. The role of clonidine in restoring the function of the septo-hippocampal input in partially fornix-damaged rats through a noradrenergic modulation of hippocampal acetylcholine release is discussed.

Acetylcholinesterase↗
PubMed1997

Comparison of effects of global cerebral ischaemia on spatial learning in the standard and radial water maze: relationship of hippocampal damage to performance.

Groups of rats which had undergone global ischaemia for 10, 15 or 20 min using the four-vessel occlusion technique were compared with sham-operated controls on learning to locate a submerged platform in both acquisition and working memory tasks in a standard Morris water maze, and in a working memory task in an eight-channel water radial maze. Ischaemic rats showed duration-related impairments in all three tasks. The water radial maze task was learned more slowly than standard water maze tasks, but deficits were long-lasting. In the first phase of training in the radial water maze controls were more reluctant than ischaemic rats to visit all arms of the maze, and were subsequently found to spend less time on the open arms of an elevated plus-maze. However, differences in anxiety are not likely to account for differences in working memory performance in the radial water maze, as groups showed similar error rates before and after habituation to the maze. Histological examination showed that cell loss occurred chiefly in the CA1 field of the hippocampus and was linearly related to duration of occlusion. Cell loss was significantly correlated with the extent of impairment, but the pattern of relationships varied across the different tasks. For water maze acquisition, deficits in latency, heading angle and time spent in the training quadrant related more strongly to CA1 than CA3 cell loss, but radial water maze impairments showed the reverse tendency. In all cases correlations were substantially reduced following exclusion of rats with maximal CA1 cell loss, although a modest relationship with CA1 damage remained for latency in acquisition and working memory tasks, and heading angle on the probe trial. These results suggested that relationships between water maze impairments and cell loss are robust only after near total destruction of the dorsal CA1 field.

Animals↗
PubMed1997

Spatial learning induces neurogenesis in the avian brain.

It is known from previous work that neurones are born continuously in the ventricular zone of the bird brain. In this study, we show that the amount of cell proliferation in the ventricular zone of the hippocampus (HP) and the hyperstriatum ventrale (HV) is influenced by behavioural experience. Two groups of birds (marsh tits) were compared: those allowed to store and retrieve food once every 3 days between days 35 and 56, and age-matched controls treated in an identical way, except that they were not allowed to store and retrieve food. After three trials of storing and retrieval, between days 35 and 41 posthatch, experienced birds showed a significantly higher rate of cell proliferation than did controls. The experienced birds also showed a significant increase in total cell and neuronal number by day 56 posthatch, after eight trials of storing and retrieval. There were no significant differences in the amount of programmed cell death in the hippocampus in this study. In a novel analysis of the data we demonstrate that the effect of experience between days 35 and 41 was to increase the daily rate of neurogenesis in the ventricular zone from 3.9 to 10%, and that this change could account for the increase in total hippocampal neuronal number by day 56 in the experienced birds. Thus, the observed increase in hippocampal volume and neuronal number as a result of food storing and retrieval, may be caused by an increase in neurogenesis in the first few trials of food storing experience.

Animals↗
PubMed1997

Effects of extended electrical kindling on exploratory behavior and spatial learning.

Short-term electrical kindling, a widely used experimental model of epilepsy, appears to have little effect on behavior. The effects of extended kindling are largely unknown. Rats implanted with kindling electrodes in amygdala (AM) or perforant path (PP) received 300 kindling trials over approximately 7 months, and were tested in the Morris watermaze after a 7-10 day recovery period. Kindled animals were impaired during the initial training on hidden-platform acquisition, but not in retention of platform location. No deficits were found in acquiring a new hidden-platform location, latency to reach a visible-platform, or in swim speed. Open-field activity showed a sustained increase when tested during kindling, but only a transient increase when tested following suspension of kindling. Similar results were obtained for both AM and PP kindled animals. Hence, long-term kindling of both of these sites produced behavioral changes that were transient in nature. Further, these results also indicate that propagation of seizure activity from remote sites can alter hippocampally-mediated or related behavior.

Animals↗
PubMed1997

Developmental lead exposure causes spatial learning deficits in adult rats.

Groups of male rats exposed to lead (Pb) during different developmental periods were tested as adults in a water maze. A highly significant (P < 0.01) impairment in water maze performance was measured in rats exposed to Pb only during gestation and lactation (maternal exposure). At the time of testing (100-106 days old), blood and brain Pb concentrations were at control levels. Significant impairments (P < 0.05) were also present in rats continuously exposed to Pb from conception through adulthood. Post-weaning Pb exposure alone did not result in impaired performance despite significantly elevated blood and brain Pb levels at the time of testing. This study supports the hypothesis that a window of vulnerability to Pb neurotoxicity exists in the developing brain and that Pb exposure can result in long-term cognitive deficits.

Analysis of Variance↗
PubMed1999

Effects of oral administration of the competitive N-methyl-D-aspartate antagonist, CGP 40116, on passive avoidance, spatial learning, and neuromotor abilities in mice.

The effects were investigated of the potent competitive N-methyl-D-aspartate (NMDA) receptor antagonist CGP 40116[D-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid] on the performance of mice in water maze and passive avoidance tasks, and in wire suspension, rotarod, and cage activity tests. The drug was administered per os (p.o.) in its anticonvulsant dose range. CGP 40116 dose-dependently impaired passive avoidance learning when given before, but not when given after training. The antagonist (5, 10, and 20 mg/kg, administered 4 h before each training session) dose-dependently affected water maze acquisition, and impaired retention test performance in both hidden- and visible-platform water maze tasks. In addition, the drug dose-dependently decreased swimming speed during water maze acquisition. Repeated administration of CGP 40116 (20 mg/kg, p.o.) persistently decreased cage activity and wire suspension test performance, whereas motor coordination and equilibrium on the rotarod apparatus remained unimpaired. In our administration protocol, no tolerance was found to the effects of the drug on passive avoidance learning and neuromotor abilities. The parallel effects of CGP 40116 on memory and motor performance are discussed, and it was concluded that the antagonist impairs neuromotor abilities and also induces memory impairments which cannot be entirely reduced to motor interference.

2-Amino-5-phosphonovalerate↗
PubMed1997

Effects of acute daily administration of diazepam on spatial learning and working memory.

This study evaluated the acute or daily effects of diazepam (DZP) on the acquisition and performance of rats in an 8-arm radial maze. Male Wistar rats (200-250 g) were divided into three groups: saline-saline (SS), saline-DZP (SD) and DZP-DZP (DD). The SS group always received intraperitoneal (i.p.) saline (SAL) in daily or acute treatments. The SD group received SAL (i.p.) daily during the task acquisition (30 days), DZP (2.5 mg/kg, i.p.) 45 min before the acute 5 s and 1 h delay tests, and it also received DZP (10 mg/kg, i.p.) for 70 days. The DD group received DZP (10 mg/kg, i.p.) daily during 30 days in the task acquisition, DZP (2.5 mg/kg, i.p.) 45 min before the acute 5 s and 1 h delay tests and further received DZP (10 mg/kg, i.p.) for an additional 70 days. Our results showed that as compared to control (SS group), 8-10 h prior administration of a single daily dose of DZP (10 mg/kg) did not alter the learning and the performance of short- (5 s delay) and long-term (1 h delay) working memory. However, the acute administration of DZP (2.5 mg/kg) impaired the performance of the short delay task (5 s delay) in animals previously exposed (DD group) or not (SD group) to daily DZP treatment. Therefore, the acute administration of an anxiolytic dose of DZP (2.5 mg/kg) produced a significant impairment of short-term working memory, even in animals exposed to daily DZP treatment for a long time.

Animals↗
PubMed2002

Effects of developmental exposure to lead, magnesium and zinc mixtures on spatial learning and expression of NMDA receptor subunit mRNA in Fischer 344 rats.

The N-methyl-D-aspartate receptor (NMDAR) is important for learning. Lead (Pb) exposure impairs learning ability and affects the NMDAR. This study tested whether developmental exposure to a combination of Pb, zinc (Zn), and magnesium (Mg) would result in effects different from those seen with individual metals. Fischer 344 (F344) rat pups of both genders were exposed from gestation day 5 to post-natal day (PND) 40, either to Pb, Mg, or Zn individually or to a (one-third or full concentration) mixture of the three metals. All Zn-treated pups died before PND7, but half of the litters given the full concentration mixture survived to PND40. Impaired learning in the Morris water maze was seen in the Mg and full concentration mixture groups. There were gender differences in NR2A subunit mRNA expression in the hippocampal CA3 region in the Mg and Pb groups, but combining the three metals in the full concentration showed no gender effect. Our results showed that exposure to all three metals affected mortality, learning ability and gender-dependent expression patterns of an NMDAR subunit in a different way from that seen with exposure to the individual metals.

Animals↗
PubMed1996

Further studies of the role of hippocampal synaptic plasticity in spatial learning: is hippocampal LTP a mechanism for automatically recording attended experience?

Rats trained as normal animals on a delayed matching-to-place task until they were fully familiar with the environment and the strategy required for effective performance were treated with a CSF or D-AP5 at a dose shown to be sufficient to block LTP in vivo. A striking delay-dependent impairment was observed in the AP5-treated animals. These findings indicate that 1-trial event memory depends on NMDA receptors.

2-Amino-5-phosphonovalerate↗
PubMed2003

Central galanin administration blocks consolidation of spatial learning.

Galanin is a neuropeptide that inhibits the evoked release of several neurotransmitters, inhibits the activation of intracellular second messengers, and produces deficits in a variety of rodent learning and memory tasks. To evaluate the actions of galanin on encoding, consolidation, and storage/retrieval, galanin was acutely administered to Sprague-Dawley rats at time points before and after training trials in the Morris water maze. Intraventricular administration of galanin up to 3h after subjects had completed daily training trials in the Morris water task impaired performance on the probe trial, indicating that galanin-blocked consolidation. Pretreatment with an adenylate cyclase activator, forskolin, prevented the deficits in distal cue learning produced by galanin. Di-deoxyforskolin, an inactive analog of forskolin, had no effect. These results provide the first evidence that galanin interferes with long-term memory consolidation processes. A potential mechanism by which galanin produces this impairment may involve the inhibition of adenylate cyclase activity, leading to inhibition of downstream molecular events that are necessary for consolidation of long-term memory.

Adenylyl Cyclases↗
PubMed1991

Spatial learning deficits in adult children of alcoholic parents.

This study investigated whether the visuospatial deficits displayed by chronic alcoholics are present in persons at risk for alcoholism. Participants were 34 matched social drinkers, half of whom were children of alcoholic parents and half of whom had no family alcoholism history. Ss with a family history of alcoholism displayed visuospatial learning that was significantly poorer than that displayed by Ss with no family alcoholism history. The learning patterns displayed by those with a family alcoholism history were similar to those displayed by previously studied detoxified alcoholics and young children of alcoholics using a similar learning task. Data suggest that visuospatial learning deficits may reflect an antecedent to rather than a consequence of chronic alcohol abuse.

Adult↗
PubMed1993

Perceptual and cognitive spatial learning.

Ss were taught novel mappings between visual space and motor space with either a variant on a prism adaptation paradigm (Experiments 1 and 2) or a nonperceptual cognitive task (Experiments 3 and 4). First, discrimination training specified that 1 visual location required a new pointing response but another location did not. This led to unusual generalization unlike typical generalization decrement. Second, training at 9 locations specified that 1 location required a new response but that the remaining 8 did not. This simple isolation mapping was unlearnable and instead a flat function fit through all of space. In contrast, for the cognitive paradigm, not only was isolation of one region of space easily learned, it was the preferred pattern of generalization. Implications for perceptual learning, as well as the qualitative distinctions between perceptual and cognitive learning, are discussed.

Adult↗
PubMed1992

Studies in spatial learning. I. Orientation and the short-cut. 1946.

1. The original rough formulation of the expectancy theory is difficult to distinguish from the alternative stimulus-response doctrines. Part of this difficulty results from the fact that implicit in this rough formulation, is a definition of the matrix "x expects a goal at location L," which makes it equivalent to the matrix "x runs down the practiced path," when certain conditions are fulfilled. Because of this difficulty, we have rejected this definition. 2. We have suggested instead a definition of the matrix "x expects a goal at location L" which makes it equivalent to the matrix "x runs down the path which points directly to the location L," when certain conditions are fulfilled. 3. To determine whether rats will run down such a path, whenever the original path is blocked, we have run 56 female rats in a situation which conformed to these conditions. 4. Thirty-six percent of the rats chose the path which pointed directly towards the location of the goal. The remaining rats were distributed over the other paths in a chance fashion. 5. We have concluded (1) that rats do learn to expect goals in specific locations, (2) that there are important similarities between this behavior and human symbolic behavior, and (3) that these similarities justify our using the word 'expectation' as a name for the disposition to short-cut when the original patch is blocked.

Animals↗
PubMed2005

Multiple systems for spatial learning: dead reckoning and beacon homing in rats.

Rats homed with food in a large lighted arena. Without visual cues, they used dead reckoning. When a beacon indicated the home, rats could also use the beacon. Homing did not differ in 2 groups of rats, 1 provided with the beacon and 1 without it; tests without the beacon gave no evidence that beacon learning overshadowed dead reckoning (Experiment 1). When the beacon was at the home for 1 group and in random locations for another, there was again no evidence of cue competition (Experiment 2). Dead reckoning experience did not block acquisition of beacon homing (Experiment 3). Beacon learning and dead reckoning do not compete for predictive value but acquire information in parallel and are used hierarchically.

Animals↗