Spatial memory in pigeons on a four-arm radial maze.

Examined spatial memory in 6, 8-arm maze experienced pigeons, using a 4-arm radial maze. The maze arms were spaced at 90° intervals, extending radially from a central choice area. Ss were forced into 3 arms, then permitted 2 choices to enter the remaining arm. Five Ss chose accurately (90% correct) with delays of 5 min or less, their choices depended on extramaze cues, and the food in the target arm provided no essential cues. After an incorrect 1st choice, Ss' 2nd choices were more accurate than chance. Data suggest that, while spatial memory has many similar characteristics in rats and pigeons, pigeon spatial memory appears less durable. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential ontogeny of working memory and reference memory in the rat.

Examined the ability of 15-, 21-, and 27-day-old rats to perform 2 spatial working memory problems (delayed alternation and discrete-trials delayed alternation) and a reference memory problem (position habit) in a T-maze. In the delayed alternation problem, each S was presented with a series of free-choice trials and was rewarded for regularly alternating responses to the left and right arms of the T-maze. In the discrete-trials delayed alternation problem, each S was forced to one maze arm and rewarded (forced run) and was then placed back into the start box and given a choice of arms (choice run). The direction of forced runs followed an irregular, counterbalanced series, and Ss were rewarded for choosing the alternate maze arm on choice runs. In the position habit problem, Ss were rewarded for consistently choosing 1 of the 2 arms of the T-maze. At all ages, rat pups learned to perform the delayed alternation and position habit problems. Only 21- and 27-day-old rats were able to learn the discrete-trials delayed alternation problem. Results of these experiments show that reference memory capacity is present by at least 15 days of age in the rat and does not develop further at later ages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does a cognitive map guide choices in the radial-arm maze?

15 rats performed in a standard radial-arm maze task (Exp 1) and in a modified task with a set of forced choices and a 15-min retention interval prior to completion of the maze (Exp 2). In addition to the standard measure of choice in the radial-arm maze, orientation toward arms was measured and considered to constitute go–no-go "microchoice" decisions. Rats investigated but rejected many arms. A model of choice was developed in which it was assumed that choice decisions about arms were made independently and that microchoices were not selectively guided toward baited arms. The model performed nearly as well as the rats. These results place important limitations on the theory that choice behavior in the radial-arm maze is guided by a cognitive map. (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)     

Entorhinal-perirhinal lesions impair performance of rats on two versions of place learning in the Morris water maze.

The effects of entorhinal–perirhinal lesions in rats were studied with 2 versions of a place learning task in the Morris water maze. These lesions impaired performance on a multiple-trial task (3 days of 6 trials and a probe trial). This assessment was followed by a task in which rats were repeatedly trained to find novel locations with a variable delay (30 sec or 5 min) imposed between each sample trial and retention test. Entorhinal–perirhinal damage produced a delay-dependent deficit in spatial memory: Rats with lesions were impaired at the 5-min delay relative to the control group and to their own performance at 30 sec. These findings are discussed in relationship to memory impairment after entorhinal damage and spatial learning deficits observed after hippocampal damage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial learning by rats across visually disconnected environments

Two spatial tasks were designed to test specific properties of spatial representation in rats. In the first task, rats were trained to locate an escape hole at a fixed position in a visually homogeneous arena. This arena was connected with a periphery where a full view of the room environment existed. Therefore, rats were dependent on their memory trace of the previous position in the periphery to discriminate a position within the central region. Under these experimental conditions, the test animals showed a significant discrimination of the training position without a specific local view. In the second task, rats were trained in a radial maze consisting of tunnels that were transparent at their distal ends only. Because the central part of the maze was non-transparent, rats had to plan and execute appropriate trajectories without specific visual feedback from the environment. This situation was intended to encourage the reliance on prospective memory of the non-visited arms in selecting the following move. Our results show that acquisition performance was only slightly decreased compared to that shown in a completely transparent maze and considerably higher than in a translucent maze or in darkness. These two series of experiments indicate (1) that rats can learn about the relative position of different places with no common visual panorama, and (2) that they are able to plan and execute a sequence of visits to several places without direct visual feed-back about their relative position.     

Partial hippocampal kindling affects retention but not acquisition and place but not cue tasks on the radial arm maze

The performance of rats that were partially kindled in the hippocampus was assessed on an 8-arm radial arm maze with 4 baited arms. In rats first trained and then kindled, deficits were found on a place task in which rats reached the goal arms of the maze using salient extramaze spatial cues, but not on an intramaze cue task in which rats reached the goal arms using salient intramaze cues. Acquisition of a new place task on the maze was not different between kindled and control rats. In conclusion, partial hippocampal kindling disrupted the retention but not the acquisition of a spatial or place task; retention of a nonspatial cue task was not disrupted.     

Spatial guidance of choice behavior in the radial-arm maze.

In 6 experiments, the performance of male rats in a 12-arm radial maze was examined. The focus of study was the extent to which the spatial location of individual baited maze arms was determined before the rat was exposed to the extramaze visual cues corresponding to the arm, and thereby guided the rat toward the location of baited arms. Such spatial guidance of choice behavior implies a spatially organized cognitive representation of maze arms (i.e., a cognitive map). A higher level of spatial guidance was found when visual access to extramaze cues was restricted than when it was unrestricted. There was no evidence of a difference between the level of spatial guidance in the context of working memory performance and reference memory performance. Some evidence that intramaze cues contributed to microchoice guidance was found. However, spatial guidance, under at least some conditions, is best explained in terms of cognitive mapping. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Newborn organ weight and spontaneous hypertension: recombinant inbred strain study

This study investigated the effects of neonatal hippocampal ablation on the development of spatial learning and memory abilities in rats. Newborn rats sustained bilateral electrolytic lesions of the hippocampus or were sham-operated on postnatal day 1 (PN1). At PN20-25, PN50-55, or PN90-95, separate groups of rats were tested in a Morris water maze on a visible "cue" condition (visible platform in a fixed location of the maze), a spatial "place" condition (submerged platform in a fixed location), or a no-contingency "random" condition (submerged platform in a random location). Rats were tested for 6 consecutive days, with 12 acquisition trials and 1 retention (probe) trial per day. During acquisition trials, the rat's latency to escape the maze was recorded. During retention trials (last trial for each day, no escape platform available), the total time the rat spent in the probe quadrant was recorded. Data from rats with hippocampal lesions tested as infants (PN20-25) or as adults (PN50-55 and PN90-95) converged across measures to reveal that 1) spatial (place) memory deficits were evident throughout developmental testing, suggesting that the deficits in spatial memory were long-lasting, if not permanent, and 2) behavioral performance measures under the spatial (place) condition were significantly correlated with total volume of hippocampal tissue damage, and with volume of damage to the right and anterior hippocampal regions. These results support the hypothesis that hippocampal integrity is important for the normal development of spatial learning and memory functions, and show that other brain structures do not assume hippocampal-spatial memory functions when the hippocampus is damaged during the neonatal period (even when testing is not begun until adulthood). Thus, neonatal hippocampal damage in rats may serve as a rodent model for assessing treatment strategies (e.g., pharmacological) relevant to human perinatal brain injury and developmental disabilities within the learning and memory realm.     

Spatial memory deficits in a virtual radial arm maze in amnesic participants with hippocampal damage.

Extensive research with laboratory animals indicates that the hippocampus is crucial for the formation and use of spatial memory. Hippocampal lesions in rodents impair spatial memory on radial arm maze tasks. It is unknown whether amnesic patients with hippocampal damage would exhibit similar impairments on a virtual version of a radial arm maze. To evaluate the importance of the hippocampus in spatial learning and memory, we tested amnesic participants with hippocampal damage in a virtual radial arm maze environment. The virtual radial arm maze required participants to learn and remember 4 rewarded arms of 8 total arms. Spatial learning and memory were assessed using the participants' ability to use salient distal cues in the virtual room to remember the 4 rewarded arms. Amnesic participants' latencies were longer and distance traveled was greater to the rewarded arms compared with nonamnesic participants. Amnesic participants made more errors than nonamnesic participants by either entering nonrewarded arms or by revisiting previously entered arms. These data are analogous to previous animal research. Overall, the human hippocampus is necessary for spatial memory and navigation in a virtual radial arm maze task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential involvement of the dorsal anterior cingulate and prelimbic–infralimbic areas of the rodent prefrontal cortex in spatial working memory.

[Correction Notice: An erratum for this article was reported in Vol 112(4) of Behavioral Neuroscience (see record 2008-09590-001). Figure 1 (page 295) and Figure 4 (page 299) were printed incorrectly. The corrected figure pages and corresponding captions are provided in the erratum.] The present study examined the effects of quinolinic acid lesions of the dorsal anterior cingulate and prelimbic–infralimbic cortices on spatial working memory and spatial discrimination using go/no-go procedures. All testing occurred in a 12-arm radial maze. In a working memory task, rats were allowed to enter 12 arms for a cereal reward. Three or 4 arms were presented for a 2nd time in a session, which did not result in a reward. In a spatial discrimination task, rats had successive access to 2 different arms. One arm always contained a reward, and the other never contained a reward. Prelimbic–infralimbic lesions impaired spatial working memory but only produced a transient spatial discrimination deficit. Dorsal anterior cingulate lesions did not induce a deficit in either task. These findings suggest that the prelimbic–infralimbic cortices, but not the anterior cingulate cortex, are important in spatial working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory in pigeons on the radial maze.

A series of 7 experiments with 10 pigeons showed, contrary to recent suggestions that pigeons show little or no spatial memory on the radial maze, highly accurate performance by Ss on an 8-arm radial maze. In Exp I, Ss were trained on successive phases that raised the number of alleys to be remembered from 1 to 4. In Exp II, Ss were allowed to search the maze for food with all 8 arms open. Measures of spatial memory showed that Ss performed at a level equivalent to that found with rats in previous research by A. B. Bond et al (see record 1982-25052-001). In Exp III, testing with massed trials revealed proactive interference. Ss were able to form reference memory for subsets of baited and unbaited alleys in Exp VI. In Exp VII, Ss learned about quantities of food associated with 4 different alleys and ordered their alley choices from the largest to the smallest reward. Contrary to the previous findings with rats, Ss in Exp IV showed forgetting over retention intervals of 0–360 sec between forced and free choices. It is concluded that spatial memory in pigeons generally shows the same properties as that in rats. (49 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Discrimination learning requiring different memory components in rats: Age and neurochemical comparisons.

Three experiments compared the performances of 19 young (8–9 mo old) and 23 aged (22–24 mo old) male ACI rats in a T-maze involving a spatial discrimination in the stem of the T-maze that required long-term reference memory, and discrete-trial, alternation discrimination in the arms of the T-maze that required working memory. Following acquisition training in 1 maze, Ss were trained in a 2nd maze in which the correct response in stem was opposite to that in the 1st maze. In Exps I and II, aged Ss made more errors in all phases of maze training than did young Ss, suggesting that all components of memory processing were affected equivalently. In Exp III, aged Ss were unimpaired in the ability to perform in a T-maze task involving a brightness discrimination with intramaze cues. This result suggests that the age-related impairment in the 2-component T-maze task was restricted to the cognitive demands of the task. Neurochemical analyses revealed a slight (8%) but significant age-related decline in the activity of glutamic acid decarboxylase but not of choline acetyltransferase. Although the correlation between maze performance and regional enzyme activities generally supported previous observations, the only significant correlation to emerge was between working memory performance and glutamic acid decarboxylase activity in the cingulate cortex. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of NMDA-induced retrohippocampal lesions on performance of four spatial memory tasks known to be sensitive to hippocampal damage in the rat

Four separate cohorts of rats were employed to examine the effects of cytotoxic retrohippocampal lesions in four spatial memory tasks which are known to be sensitive to direct hippocampal damage and/or fornix-fimbria lesions in the rat. Selective retrohippocampal lesions were made by means of multiple intracerebral infusions of NMDA centred on the entorhinal cortex bilaterally. Cell damage typically extended from the lateral entorhinal area to the distal ventral subiculum. Experiment 1 demonstrated that retrohippocampal lesions spared the acquisition of a reference memory task in the Morris water maze, in which the animals learned to escape from the water by swimming to a submerged platform in a fixed location. In the subsequent transfer test, when the escape platform was removed, rats with retrohippocampal lesions tended to spend less time searching in the appropriate quadrant compared to controls. Experiment 2 demonstrated that the lesions also spared the acquisition of a working memory version of the water maze task in which the location of the escape platform was varied between days. In experiment 3, both reference and working memory were assessed using an eight-arm radial maze in which the same four arms were constantly baited between trials. In the initial acquisition, reference memory but not working memory was affected by the lesions. During subsequent reversal learning in which previously baited arms were now no longer baited and vice versa, lesioned animals made significantly more reference memory errors as well as working memory errors. In experiment 4, spatial working memory was assessed in a delayed matching-to-position task conducted in a two-lever operant chamber. There was no evidence for any impairment in rats with retrohippocampal lesions in this task. The present study demonstrated that unlike direct hippocampal damage, retrohippocampal cell loss did not lead to a general impairment in spatial learning, implying that the integrity of the retrohippocampus and/or its interconnection with the hippocampal formation is not critical for normal hippocampal-dependent spatial learning and memory. This outcome is surprising for a number of current hippocampal theories, and suggests that other cortical as well as subcortical inputs to the hippocampus might be of more importance, and further raises the question regarding the functional significance of the retrohippocampal region.     

Role of retroactive interference in the spatial memory of normal rats and rats with hippocampal lesions.

Studied the importance of retroactive interference (RI) in memory for spatial locations by using a 12-arm radial maze and a standard RI paradigm. 26 male albino Sprague-Dawley rats in the RI condition first learned to choose 4 of the 12 arms, followed by training to a 2nd set of 4 arms. In the control condition for interference, Ss learned the 1st set of arms but were not trained to approach the 2nd set. Thereafter, Ss in each interference condition were assigned to groups (hippocampal, cortical control, or unoperated control), the operations were carried out, and then all Ss were tested for retention of the set of arms learned first. Contrary to predictions of the cognitive map theory (J. O'Keefe and L. Nadel, 1978), RI was found in control Ss. The severe memory deficit found in hippocampals was not influenced by the interference variable. In addition to impaired performance early in relearning, Ss with hippocampal lesions continued to make many errors throughout the 10 wks of testing, including choices to unbaited arms and repeated entries into baited arms. However, hippocampals eventually learned not to reenter unbaited arms. Data indicate a deficit in the selection and utilization of sets of responses and are interpreted as implicating the hippocampus in retrieval processes. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food searching strategies of rats: Variables affecting the relative strength of stay and shift strategies.

Examined the extent to which the food searching strategies of rats are influenced by training, information about food in an initially visited site, and type of memory required for correct choices. Exp I used a discrete-trial, delayed conditional-discrimination procedure on a T-maze with 32 male Sprague-Dawley rats. Ss entered 1 arm of the maze and were given a choice between that arm (stay strategy) or the other arm (shift strategy). During the initial visit, S either consumed all the food (depletion condition) or only some of it (nondepletion condition). Ss given the shift-depletion task learned most rapidly; those given the stay-depletion task learned most slowly. Depletion increased the rate at which the shift discrimination was learned but decreased the rate at which the stay discrimination was learned. Exp II used a similar procedure with the Maier 3-table maze and 16 male albino rats; the same pattern of results was found. Exp III, conducted with 15 male Sprague-Dawley rats, required each S to learn both a win-stay and a lose-shift contingency and to use associative memory. Early in training, Ss used only a shift strategy but eventually learned the discrimination. Results indicate that the shift-stay balance is influenced by the rat's species-specific predisposition, reinforcement contingencies, amount of food in the initially visited place, and the extent to which recognition memory by itself is sufficient to solve the discrimination. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of cytotoxic perirhinal cortex lesions on spatial learning by rats: A comparison of the dark Agouti and Sprague-Dawley strains.

The effects of perirhinal cortex lesions in rats on spatial memory might depend on the choice of strain. The present study, therefore, compared perirhinal lesions in Sprague-Dawley rats (associated with deficits) with Dark Agouti rats (associated with null effects). Tests of reference memory and working memory in the water maze failed to provide evidence that perirhinal lesions disrupt overall levels of performance (irrespective of strain) or that these lesions have differential effects on the rates of spatial learning in these 2 strains. Strain differences were, however, found, as the Dark Agouti strain was often superior. Furthermore, the perirhinal lesions did have differential effects in the 2 strains, but these did not appear to relate directly to changes in spatial learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Redistribution of spatial representation in the hippocampus of aged rats performing a spatial memory task.

Young and old rats performed on a maze according to a forced-choice and then a spatial memory procedure either in the same or a different environment. Aged rats were slower to learn the spatial memory task when tested in the same, but not in a different, room. One interpretation of this pattern of results is that although old rats learn new rules as quickly as young rats, they show less flexibility with old rules and familiar spatial information. Impaired choice accuracy during asymptote performance suggests poor processing of trial-unique information by old rats. Spatial correlates of hippocampal CA1 and hilar cells varied with task demand: CA1 cells of aged rats showed more spatially selective place fields, whereas hilar cells showed more diffuse location coding during spatial memory, and not forced-choice, tests. Such representational reorganization may reflect a compensatory response to age-related neurobiological changes in the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posterodorsal septal lesions impair performance on both shift and stay working memory tasks.

Two groups of male Long-Evans rats (N?=?42) were trained preoperatively on either a shift or a stay problem in a T-maze. Training trials consisted of 2 runs, an "information run" in which S was forced to go down 1 of the 2 arms of the T-maze, followed immediately by a "choice run" in which S could choose either arm. In the shift condition, Ss were rewarded with wet mash only for choosing the arm opposite the one they entered on the information run. In the stay condition, Ss were rewarded for entering the arm that was entered on the information run. The shift group reached 100% performance accuracy after fewer trials than the stay group. Choice accuracy in both groups declined as the delay increased and returned to 100% at the 0-sec delay. Half of the Ss in each condition then received either lesions of the posterodorsal septum—aimed at disconnecting the septum and hippocampus—or control surgery. Results indicate that deficits in maze performance by Ss with septo-hippocampal damage were not restricted to tasks that require alternation of spatial locations. This finding falsifies the notion that maze deficits reflect a spontaneous alternation deficit or changed "spatial strategy," but it supports the hypothesis of a working memory deficit in these Ss. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective immunotoxic lesions of basal forebrain cholinergic cells: Effects on learning and memory in rats.

Male Long-Evans rats were given injections of either 192 IgG-saporin, an apparently selective toxin for basal forebrain cholinergic neurons (LES), or vehicle (CON) into either the medial septum and vertical limb of the diagonal band (MS/VDB) or bilaterally into the nucleus basalis magnocellularis and substantia innominata (nBM/SI). Place discrimination in the Morris water maze assessed spatial learning, and a trial-unique matching-to-place task in the water maze assessed memory for place information over varying delays. MS/VDB-LES and nBM/SI-LES rats were not impaired relative to CON rats in acquisition of the place discrimination, but were mildly impaired relative to CON rats in performance of the memory task even at the shortest delay, suggesting a nonmnemonic deficit. These results contrast with effects of less selective lesions, which have been taken to support a role for basal forebrain cholinergic neurons in learning and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)