Spatial versus nonspatial relational learning in free-ranging fox squirrels (Sciurus niger).

This experiment was designed to assess spatial and nonspatial relational learning in free-ranging squirrels. The authors tested the possible use of proximal landmarks as conditional information to predict the locations of nuts, hidden in small dishes distributed on a plastic board. Squirrels were trained to associate the presence of 1 object, at the center of the board, with 1 set of baited dishes, whereas the presence of a 2nd object, placed alternatively at the same location, was associated with another set of dishes. They did not acquire the nonspatial relational task on the basis of proximal landmarks. They developed a win-stay spatial strategy relying on directional information derived from distant visuospatial cues and neglected proximal spatial information when it conflicted. They relied on their memory of the food locations in the previous trial to predict the nuts' locations, even though the objects were the only predictors of these locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How habitat features shape ground squirrel (urocitellus beldingi) navigation.

The purpose of this investigation was to determine whether Belding's ground squirrels (Urocitellus beldingi) from areas rich in beacons perform differently in a task of spatial memory compared with squirrels from beacon-thin areas. To assess the role of environmental experience in spatial memory, wild-born squirrels with several days of experience in the field were compared with squirrels born in a lab and with no experience in their original habitat. Over two summers, squirrels captured from beacon-dense and beacon-thin areas were tested in a radial maze interspersed with beacons, using number of trials to criterion as a measure of spatial memory. To evaluate the effect of landmark navigation, in year 2 juveniles were prevented from seeing outside the maze area. In both years squirrels from beacon-dense populations reached criterion faster than squirrels from beacon-thin populations, and a weak rearing effect was present in 1 year. Despite sex differences in adult spatial skills, no differences were found between males and females in the maze. This demonstrates variation in the navigation strategies of young U. beldingi, and highlights the need to evaluate spatial preferences as a function of population or ecology in addition to species and sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control of spatial orientation in terrestrial toads (Rhinella arenarum).

Three experiments were conducted to determine problem-solving strategies used by toads, Rhinella arenarum (= Bufo arenarum), in spatial learning situations, using water as reward. Experiment 1 showed that toads can acquire a spatial orientation based on a body-centered turn -an internal self-reference cue. Experiment 2 showed that toads can use a fixed landmark (visual cue) as guidance to solve a spatial problem. Experiment 3 determined whether maze learning was based on “body-centered turn” or “guidance”. In this case, animals were trained with a fixed visual cue in relation to a body-centered turn (i.e., simultaneously with the internal self-reference cue) and then tested with the visual cue dissociated from positional cues. Toads trained with the combination of a visual cue and a body-centered turn preferred the latter (turn response) when the two sources of information were set in conflict on probe trials. Toads showed behavioral patterns similar to those described in rodents trained under similar condition, thus, suggesting an early evolutionary origin for these problem-solving strategies. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Absence of snapshot memory of the target view interferes with place navigation learning by rats in the water maze.

Contribution of visual and nonvisual mechanisms to spatial behavior of rats in the Morris water maze was studied with a computerized infrared tracking system, which switched off the room lights when the S entered the inner circular area of the pool with an escape platform. 10 naive male rats trained under light–dark (LD) conditions found the escape platform more slowly than 10 male rats trained in permanent light (LT). After group members were swapped, the LT-pretrained rats found under LD conditions the same target faster and eventually approached latencies attained during LT navigation. Performance of LD-trained rats deteriorated in permanent darkness (PD) but improved with continued PD training. Thus LD navigation improves gradually by procedural learning (extrapolation of the start-target azimuth into the zero-visibility zone) but remains impaired by lack of immediate visual feedback rather than by absence of the snapshot memory of the target view. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinction between places and paths in rats' spatial representations.

Rats were trained on a 3-dimensional, 4-arm radial maze. In Exp 1, Ss trained to climb to the single goal platform chose fewer novel routes to the goal than Ss trained to climb to the 4 spatially distinct platforms. In Exp 2, a reinforcement contingency was imposed, requiring a novel route choice on each trial to receive reinforcement. Learning to associate route choice with reinforcement outcome was much more difficult for Ss tested with the single goal than for Ss tested with the 4 distinct goals. In Exp 3, a partitioned central platform group learned the reinforcement contingency as quickly as the Ss given 4 spatially distinct platforms. In Exp 4, distinctive floor inserts did not affect performance relative to no inserts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How do animals actually solve the T maze?

Rats were trained on a reinforced, delayed alternation T-maze task in the presence (cue group) or absence (no-cue group) of salient extramaze landmarks. A surprising finding was that the acquisition and memory performance of the 2 groups did not differ. Manipulations of the extramaze landmarks for the cue group suggested that, although landmarks were used to guide behavior, other sources of information were also used normally. The no-cue group was able to perform the task at above-chance levels even when extramaze, intramaze, and inertial sources of orientation were manipulated. These results suggest that memory performance on the T maze does not rely exclusively on the processing of allocentric spatial relationships in the maze environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurotoxic lesions of the rat perirhinal cortex fail to disrupt the acquisition of performance of tests of allocentric spatial memory.

Rats with neurotoxic lesions of the perirhinal cortex (n = 9) were compared with sham controls (n = 14) on a working memory task in the radial am maze. Rats were trained under varying levels of proactive interference and with different retention intervals. Finally, performance was assessed when the maze was switched to a novel room. None of these manipulations differentially impaired rats with perirhinal lesions. Rats were next trained on delayed matching-to-place in the water maze. Even with retention delays of 30 min, there was no evidence of a deficit. Although interactions between the perirhinal cortex and hippocampus may be important for integrating object-place information, the perirhinal cortex is often not necessary for tasks that selectively tax allocentric spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of the contributions of the frontal and parietal association cortex to spatial localization in rats.

Compared 15 rats with lesions of the medial frontal, orbital frontal, or parietal cortex with 5 rats with complete removal of the neocortex and 5 normal controls on 3 spatial tasks: Morris water task, radial arm maze, and spatial reversals in a Grice box. Decortication produced severe impairments in the acquisition of all 3 tasks. Ss with parietal cortex lesions were relatively unimpaired at any of the tasks, although they had a significant deficit on the spatial reversal task and had a short-term memory impairment on the radial arm maze. In contrast, Ss with medial frontal lesions had a significant, but relatively mild, impairment on the radial arm maze and were poor at learning the water task. Ss with orbital frontal lesions were nearly as impaired on the radial arm maze and water task as decorticate Ss. Results suggest that the frontal and parietal cortex of rats play different roles in the control of spatial orientation but do not support the view that egocentric and allocentric spatial orientation are related to frontal and parietal mechanisms, respectively. In addition, results suggest that the frontal cortex plays a larger role in the control of spatially guided behavior than has been previously recognized and that both the medial frontal and the orbital frontal cortex play a dissociable role in the control of spatial orientation. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

N-methyl-D-aspartate receptor antagonist MK-801 and spatial memory representation: Working memory is impaired in an unfamiliar but not in a familiar environment.

Female Sprague-Dawley rats were injected with the noncompetitive N-methyl-D-aspartate (NMDA) antagonist MK-801 or saline 30 min before daily testing in spatial working-memory (WM) and reference memory (RM) procedures in an 8-arm radial maze. MK-801 impaired RM and WM acquisition but not performance when rats were trained to criterion before drug administration. Neither a 2-hr nor a 4-hr delay between the first and last 2 correct WM choices impaired long-term WM. MK-801 impaired WM performance in trained rats only when rats were tested in a new environment. Thus, 2 mechanisms may be required for relational memory: an NMDA-dependent mechanism for acquiring long-term spatial representations and an NMDA-insensitive mechanism for operating on these stored representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of selective immunotoxic lesions of medial septal cholinergic cells on spatial working and reference memory.

The effect of injection into the medial septum of a toxin selective for cholinergic neurons, 192 IgG-saporin, was examined in rats trained to perform 2 versions of the radial 8-arm maze task. Rats were first trained to perform a task with varying delays (0, 1, 2 min) imposed between the 4th correct arm choice and access to all 8 arms. Lesioned rats made significantly more errors in the first 4 choices compared with controls and significantly more errors after delays; however, this effect was not delay dependent. Rats were then trained on a different version of this 8-arm maze task in which they learned to avoid 2 arms that were never baited. There was no treatment effect on acquisition of this task. These data are consistent with the hypothesis that the cholinergic projection to the hippocampus facilitates the acquisition of information into the system responsible for short-term memory for locations visited (spatial working memory) but is not involved in retention of this information. It also appears to play no role in either the acquisition or retention of place-nonreward associations (spatial reference memory). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial septal lesions in rats produce permanent deficits for strategy selection in a spatial memory task.

Rats with medial septal (MS) lesions have been shown to consistently use a stereotypic response strategy rather than a nonstereotypic spatial learning strategy when solving a radial maze task. The present study examined the long-term effects of MS lesions on spatial memory performance to determine whether MS lesions permanently impair rats from using a nonstereotypic strategy. Male rats, initially trained on a radial maze, were given either MS or sham surgeries and were subsequently retested on the maze. Consistent with previous studies, all Ss with MS lesions used a stereotypic strategy during the postoperative retest. However, when placed through a series of retraining phases that required the S to use a nonstereotypic strategy to solve the task, none of the MS Ss could solve the task. These results indicate that lesions of the MS produce permanent spatial memory deficits that cannot be restored through extensive behavioral training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relative importance of global and local landmarks in navigation by Columbian ground squirrels (Spermophilus columbianus).

In order to survive, small burrowing mammals need to remember the locations of escape burrows. Therefore, it is important to know what types of landmarks are used to aid navigation in the wild. The author tested the ability of free-ranging Columbian ground squirrels (Spermophilus columbianus) to locate escape burrows when local (e.g., vegetation pattern, local relief), global (e.g., forest edge, mountain outline), or both types of landmarks were obstructed. Results suggest that squirrels need both local and global landmarks of the environment for successful navigation, and that the upper portion of the horizon is especially important for orientation. Moreover, the lack of information from one type of landmark (local or global) cannot be completely compensated by the other type. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective hippocampal lesions: Differential effects on performance by rats of a spatial task with preoperative versus postoperative training.

102 male Sprague-Dawley rats with selective lesions involving different hippocampal cell fields and/or projections either learned a complex spatial maze postoperatively or were trained preoperatively and tested after the operations. Following damage to anterdorsal CA1 cells and the alveus, acquisition was impaired, but performance was normal when the task was learned preoperatively; postoperative acquisition and performance of the preoperatively learned task were impaired in animals with fimbrial lesions. Data suggest that the CA1 cell field and the projections to the subiculum play an important role in the acquisition of new spatial information but that these connections are not necessary for the utilization of spatial information learned preoperatively. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial disorientation blocks reliable goal location on a plus maze but does not prevent goal location in the Morris maze.

Cue control in spatial learning was investigated in a plus maze and a Morris maze. Rats transported in opaque containers with prior rotation to a plus maze, but not a Morris maze, could not find a goal defined by external cues. Rats transported in clear containers without rotation found the goal in both mazes. In the Morris maze, goal location was readily relearned following cue removal by rats in clear containers but not by rats in the opaque/rotation group. B. L. McNaughton et al's (1996) theory that during spatial learning sensory information is bound to preconfigured internal maps in the hippocampus, whose metric is self-notion and whose orientation depends on input from an inertial based head direction system, may explain this study's findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of the goal on children's exploration and memory of large-scale space.

Investigated developmental differences in spatial exploration and memory depending on the purpose for which 32 6–7 and 8–9 yr olds explored the space. Ss were instructed prior to exploring a funhouse to attend to either the layout of the space or the route through the space. Ss given instructions to study the layout studied and remembered more layout-relevant information, such as the number and location of dead-end rooms and the relations between spatial features, than did those in the route condition; this same pattern was found for the 6–7 and the 8–9 yr olds. Results suggest that layout knowledge includes knowledge of routes, that layout rather than route knowledge emphasizes the interrelationship of spatial information, and that the acquisition of route or layout knowledge depends on the purpose of obtaining the information. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sun compass and landmark orientation by black-capped chickadees (Parus atricapillus).

Black-capped chickadees (Parus atricapillus), nutcrackers, and jays use a variety of visual cues to relocate and retrieve hidden food caches. Results with scrub jays (Aphelocoma coerulescens) show that sun compass orientation may play an important role in cache retrieval. In a series of experiments, black-capped chickadees were trained to find food along 1 side of an octagonal cage and then subjected to a photoperiodic phase shift to test for the use of sun compass orientation. In some experimental conditions, search was influenced by sun compass information, even when this produced search in conflict with local landmarks. In other conditions, however, there was no indication that birds used the sun compass for orientation. Sun compass orientation by chickadees may depend on the nature and availability of familiar landmarks. Directional information provided by the sun compass is probably integrated with local landmark information, and may require local landmark information, to produce oriented spatial search by chickadees. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of spatial information processing in aged rats.

The spatial learning abilities of young, middle-age, and senescent rats were investigated in 2 experiments using several versions of the Morris water maze task. In Exp I, Long-Evans hooded rats were trained to find a submerged escape platform hidden within the water maze. Aged Ss exhibited acquisition deficits compared with either young or middle-age Ss. With continued training, all age groups eventually achieved comparable asymptotic levels of performance. To identify the basis of the age-related impairments observed in Exp I, naive young and aged Ss in Exp II were initially tested for their ability to locate a cued escape platform in the water maze. The escape latencies of both young and aged Ss rapidly decreased to equivalent asymptotic levels. Following cue training, young Ss exhibit a significant spatial bias for the region of the testing apparatus where the platform was positioned during training. In contrast, aged Ss showed no spatial bias. Training was continued in Exp II using a novel submerged platform location for each S. During these place training trials, the escape latencies of senescent Ss were longer than those of young Ss. These impairments were also accompanied by a lack of spatial bias among aged Ss relative to young controls. Results indicate that age-related impairments in water maze performance reflect a specific deficit in the ability of aged rats to utilize spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural Correlates of Individual Differences in Spatial Learning Strategies.

Behavioral studies have shown that spatial skills, such as mental rotation, are correlated with preferences for certain types of spatial information. To be more specific, better mental rotation is associated with a preference for survey (maplike) spatial information relative to route (landmark or wayfinding) information. Functional MRI was used to investigate how individual differences in spatial skills (mental rotation) interact with encoding information from these 2 spatial perspectives. Despite similarities in performance across individuals for route and survey learning, differences between route and survey encoding activation increased with increased mental rotation ability in anterior cingulate, middle frontal gyrus, and postcentral gyrus. This correlation appeared to be due to decreasing activation during survey encoding and not activation changes during route learning. The results suggest that mental rotation skill contributes to survey or map learning but that alternative strategies can be used under the circumstances of this study to achieve equal performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial learning in a T-maze by the crayfish Orconectes rusticus.

The T-maze has commonly been used to investigate the mechanisms underlying spatial learning in vertebrates and has yielded much information about how animals use response and place cues to orient toward a goal. We designed a T-maze to study the spatial learning abilities of crayfish (Orconectes rusticus), using tactile stimuli as a place cue and escape from warm water for reinforcement. An initial experiment found that most animals did not display a side-turning bias when first placed in the maze, and hence animals were randomly assigned to escape from the left or the right arm, one of which contained a smooth floor and the other a rough floor. We found that, over repeated trials, the latency to escape and the number of turns made prior to escaping significantly decreased indicating that crayfish learned to escape from the maze more rapidly and efficiently. Learning occurred over the course of six trials on a single day, and over 5 days of testing, providing evidence for spatial memory lasting 24 hr. In probe trials, in which experienced animals started the maze in an arm opposite to that used during training trials, crayfish did not display a preference for either response-based learning or place-based learning. Instead they engaged in renewed exploration of the entire maze. These findings suggest that, in addition to remembering the location of the exit, crayfish also remembered the overall configuration of the maze. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Mazes, maps, and memory.

Reviews the literature on the history of maze testing, focusing on the issue of behavioral stereotypy vs behavioral flexibility. Early experiments were based on the "kinesthetic machine" hypothesis, which held that (a) stimuli arise in some sort of temporal sequence from the activity of the muscles as the animal traverses the maze pattern and (b) during the process of learning this temporal sequence becomes fixed. Subsequent experiments emphasized the variability of behavior and showed that in many situations animals chose not to repeat their previous choices. J. F. Dashiell (1930), W. S. Small (1900, 1901), and others demonstrated that rats tended to explore their spatial environments in exhaustive detail. The development of the radial-arm maze, a spatial analog of the operant delayed matching-to-sample procedure, provided a means for systematic investigation of working memory in animals. Cognitive maps are discussed in terms of the sunburst maze of E. C. Tolman et al (1946) and the successful use of maplike structures with chimpanzees shown by E. W. Menzel (1973, 1978). The question of how an animal decides to search for food and the extent to which this decision process in a natural habitat is related to that in a laboratory maze is addressed. The data reviewed show that in spatial tasks, rats and other animals have the ability to remember information and to use it appropriately in a flexible, adaptive manner. (73 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)