Differential effect of ketamine on the reference and working memory versions of the Morris water maze task.

The assumption that blockade of long-term potentiation by N-methyl-D-aspartate antagonists interferes with spatial memory was supported by experiments showing that 15 mg/kg ketamine impairs acquisition of navigation to a hidden platform but not to a visible platform. Higher doses were required to impair retrieval of overtrained place navigation. In a working memory version of the task, retrieval latencies were shorter than acquisition latencies with 4- to 15-min but not with 30- and 60-min delays. Latent learning was only effective with the 4-min delay. Ketamine prolonged the initial search of the hidden platform at 3 mg/kg and impaired latent learning but not active acquisition at 1.5–20 mg/kg. Comparison of behavioral and synaptic effects of ketamine suggests that long-term potentiation is a necessary condition, but not a sufficient condition, for acquisition of place navigation, because search strategy and latent place learning are impaired by ketamine doses not interfering with this synaptic phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal lesions cause learning deficits in inbred mice in the Morris water maze and conditioned-fear task.

This study examined the effect of hippocampal lesions on acquisition of the Morris water maze and conditioned-fear task in inbred mice. C57BL/6J, DBA/2J, and B6D2F1 hybrid mice were given hippocampal lesions or sham surgery and then tested. The lesioned C57BL/6J and B6D2F1 mice failed to learn the Morris task relative to sham-operated controls, and no DBA group learned the task. In the contextual component of conditioned fear, lesions decreased freezing in all strains. But the lesions only affected freezing to the conditioned stimulus in the DBA/2J and B6D2F1 strains. These data demonstrate that C57BL/6J and B6D2F1 mice use the hippocampus to solve the Morris water maze and conditioned-fear task, and the DBA mice use the hippocampus, to some degree, in the conditioned-fear task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detailed behavioral analysis of water maze acquisition under systemic NMDA or muscarinic antagonism: Nonspatial pretraining eliminates spatial learning deficits.

A detailed behavioral analysis of water-maze acquisition showed that the N-methyl-{d}-aspartate (NMDA) antagonist NPC17742 and the muscarinic antagonist scopolamine caused sensorimotor disturbances in behaviors required for maze performance and that these correlated with acquisition impairments in both hidden and visible platform versions of the maze in male rats. Behavioral disturbances included thigmotaxic swimming, swimming over and deflecting off the platform, abnormal swim behavior, and hyperactivity. Rats familiar with the behavioral strategies involved in the task performed normally under NPC17742 or scopolamine. The results indicated that drug-induced sensorimotor disturbances contributed to poor acquisition scores in naive rats. NMDA or muscarinic activity may contribute to but do not appear to be essential for spatial learning in the water maze. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of cholinergic blockade on performance of rats in the water tank navigation task and in a radial water maze.

Tested the disruptive effect of cholinergic blockade under conditions in which either the working memory or the spatial mapping requirements of the behavioral task were emphasized. In Exp I, 13 male hooded rats were trained in an 8-arm radial water maze to asymptotic performance. When delays of 5, 10, 20, and 40 min were inserted between Choice 4 and Choice 5, incidence of errors in Choices 5–8 increased after pretrial (20 min) intraperitoneal scopolamine (0.2 mg/kg) faster than under control conditions and approached chance level with the 40-min delay. Scopolamine after Choice 4 or pretrial methylscopolamine was ineffective. In Exp II, 30 Ss were trained in a Morris water tank. Acquisition was impaired by pretrial injection (20 min) of 0.1 and 0.2 mg/kg scopolamine, but a higher dose (1.0 mg/kg) was required to impair overtrained performance. In a working memory version of the navigation task, scopolamine administered 20 min before the 1st trial deteriorated retention tested 40 min later at a dose of 1.0 but not at 0.4 and 0.2 mg/kg. It is concluded that the disruptive effect of scopolamine is proportional to the demands on the working memory component of the task, whereas the use of an overtrained mapping strategy is relatively resistant to cholinergic blockade. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of traumatic brain injury on mouse spatial and nonspatial learning in the Barnes circular maze

In order to evaluate the functional role of chemotactic cytokines in the regulation of brain function, we examined the effects of acidosis on the production of IL-8 in cultured neurons and/or astrocyte-rich cerebellar granule cells as assessed by the ELISA method. A time-dependent and significant production of IL-8 was detected in the extracellular fluid of astrocyte-rich cultured cells at 2, 3 and 6 hrs after treatment with acidified Krebs-HEPES buffer (pH 6.9), although such production did not appear in the fluid of neuron-rich cells. Additionally, microglia were detected by microscopic examination in both cultured cells under acidotic conditions. Only astrocyte-containing cultured cells produced a marked increase in intracellular IL-8 under acidotic conditions, although this production was much less than that seen in the extracellular fluid at 6 hrs under acidosis. The increase of IL-8 in astrocyte-rich cultures induced by acidosis was potentiated by treatment with glutamate, which enhanced the increase of cytosolic Ca2+ levels under acidosis, and was affected by extracellular Ca2+ conditions, by cyclosporine A, an inhibitor of calcineurin, and by trifluoperazine, an inhibitor of phospholipase A2. Significant inhibition of IL-8 production was detected after 6 hrs of pretreatment with trifluoperazine. Furthermore, the production of IL-8 under acidosis was associated with the appearance of astrocyte damage. These results suggest that Ca2+-dependent IL-8 is produced by astrocytes, but not neuronal cells, under acidosis, and that this production may be related to the process of cell dysfunction resulting from membrane destruction induced by acidosis.     

A two-platform task reveals a deficit in the ability of rats to return to the start location in the water maze.

The ability of rats to return to the start location was examined with a 4-arm radial water maze. The task required rats to find 2 hidden platforms in sequence. Rats were released from 1 of 3 arms and there was a platform located in the fourth arm. Once a rat found this platform, a 2nd platform was raised in another location, which was either the start location, for 1 group, or another fixed location, for a control group. Across 3 experiments, all rats learned the location of the 1st fixed platform in 80 to 120 trials. However, rats had difficulty finding a 2nd platform if it was at the start location. Control groups revealed that rats could learn 2 platform locations and that the difficulty in learning to return to the start location did not seem to be attributable to its aversive nature. In separate groups, exposure to the start location was increased by starting the rats from an initially stable platform. Rats still did not readily learn to return to the start location. The authors suggest that start location, when varied, cannot readily be used to define the location of a hidden platform. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pigeons may not use dual coding in the radial maze analog task.

Using a radial maze analog task, T. R. Zentall, J. N. Steirn, and P. Jackson-Smith (1990) found evidence that when a delay was interpolated early in a trial, pigeons coded locations retrospectively, but when the delay was interpolated late in the trial, they coded locations prospectively (support for a dual coding hypothesis). In Experiment 1 of the present study, the authors replicated the original finding of dual coding. In Experiments 2 and 3, they used a 2-alternative test procedure that does not require the assumption that pigeons' choice criterion, which changes over the course of the trial, is the same on delay and control trials. Under these conditions, the pigeons no longer showed evidence for dual coding. Instead, there was some evidence that they showed prospective coding, but a more parsimonious account of the results may be that the delay produced a relatively constant decrement in performance at all points of delay interpolation. The original finding of dual coding by Zentall et al. might have been biased by more impulsive choices early in control trials but not in delay trials and by a more stringent choice criterion late in delay trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of excitotoxic lesions centered on the perirhinal cortex in two versions of the radial arm maze task.

Rats with bilateral ibotenic acid lesions centered on the perirhinal cortex and sham-operated controls were tested in 2 versions of a spatially guided radial arm maze task. Lesioned rats made significantly more errors and required more sessions to reach criterion relative to controls in the standard radial maze task. When they were tested in a delayed nonmatch to sample version of this task, lesioned rats made more errors during the predelay phase and at both the 30-s and 10-min delays of the postdelay phase. These findings provide further support for the hypothesis that the role of the perirhinal cortex in object recognition memory may include reference to some spatial aspect of the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation of spatial learning of rats in the Morris water maze task to the number of viable CA1 neurons following four-vessel occlusion.

Male Wistar rats were tested in the Morris water maze task 1 wk after 6, 9, or 12 min of transient global ischemia. The 9-min and 12-min ischemia groups were significantly impaired in the acquisition and the reversal experiment. A systematic counting of CA1 neurons in the whole hippocampal formation revealed a unilateral number of CA1 neurons of 286,000 in the sham group, of which two-thirds were located in the dorsal hippocampus. The ischemia groups showed a significant decline in the number of dorsal CA1 neurons, whereas only the 12-min ischemia group showed a significant but minor decline (10–25%) in the number of ventral CA1 neurons. A correlation analysis showed that the escape distance declined with increasing number of viable CA1 neurons, but poor correlation coefficients were obtained. Thus, some of the ischemic rats with even very few viable CA1 neurons in the dorsal hippocampus were capable of performing this spatial learning task at sham-group level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human navigation that requires calculating heading vectors recruits parietal cortex in a virtual and visually sparse water maze task in fMRI.

Spatial navigation in the real-world is a complex task that involves many functions, such as landmark identification, orientation, and the calculation of heading vectors. This study uses a 2 × 2 experimental design with fMRI to isolate mnemonic and navigational processes that accompany the calculation of heading vectors. The conditions are based on a working memory version of the Morris water maze task and navigation takes place in a visually austere virtual environment. In an allocentric condition, subjects navigate around a circular arena where there is one small red square on the wall. Each trial begins with an encoding phase in which subjects locate and navigate to a visible coin. Then, in a test phase, after being randomly repositioned, they retrieve the coin when it is invisible. In a control task, there are eight distinct cues around the arena that provide direct cue-place information. Results show significant interaction effects in bilateral posterior parietal cortex, which is compatible with evidence that parietal cortex helps translating between allocentric coordinates and egocentric directions. There was also greater activation for the allocentric task in right posterior hippocampus and left retrosplenial cortex, which could be related to self-localization and orientation. The findings are also compatible with the recent proposal by Kubie and Fenton (2009) that navigation primarily depends on heading vectors between salient places. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective dysgranular retrosplenial cortex lesions in rats disrupt allocentric performance of the radial-arm maze task.

The present study provides the 1st report on the effects of selective lesions of the dysgranular portion of the retrosplenial cortex in rats. Excitotoxic lesions of the dysgranular area were sufficient to impair behavior in the radial-arm maze by biasing the strategy used to solve the task. In particular, rats with dysgranular retrosplenial lesions were less reliant on distal visual cues to control performance of a working memory task in the radial-arm maze. Instead, they were more reliant on using a motor turning strategy to solve the task. This change in strategy is consistent with anatomical data showing that the dysgranular region is the primary recipient of visual inputs to the rat retrosplenial cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for task conflict in the Stroop effect.

C. M. MacLeod and P. A. MacDonald (2000) suggested that congruent and incongruent Stroop stimuli cause more task conflict than neutral stimuli because the anterior cingulate cortex is more activated with these stimuli. This study investigated behavioral expression for this pattern. Experiment 1 reduced task conflict control by increasing the proportion of nonword neutrals. Additionally, half the trials had conflict or neutral cues. The control reduction revealed the task conflict. For noncued trials, response time was longer for congruent stimuli than for neutral stimuli (reverse facilitation effect). In addition, response time for congruent stimuli was longer when stimuli were uncued vs. cued. Experiment 2 increased task conflict control by changing the neutral stimuli to noncolor words. Consequently, the task conflict expression disappeared. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impairment in long-term retention but not short-term performance on a water maze reversal task following hippocampal or mediodorsal striatal n-methyl-d-aspartate receptor blockade.

Male Long-Evans rats were injected with 32 ng/μl of the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) or vehicle and trained to locate a hidden platform in a different location (reversal training) than used on the initial 4 days of training. Rats treated with vehicle or CPP into the dorsal hippocampus, basolateral amygdala, or mediodorsal striatum had similar latencies to locate the platform on the reversal day. Rats infused with CPP into the dorsal hippocampus or mediodorsal striatum failed to search preferentially in the novel location during a 24-hr, drug-free retention test, whereas all other groups searched preferentially in this location. Therefore, blocking dorsal hippocampal or mediodorsal striatal NMDA receptors selectively blocked long-term spatial retention without producing short-term performance deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related deficits in mice performing working memory tasks in a water maze.

This study determined whether mice exhibit spatial working memory deficits with increased age. C57BL/6JNia mice of 3 different ages were tested in the Morris water maze with 2 protocols designed to assess immediate and delayed working memory abilities. Young mice required multiple trials in order to show improvements in the working memory task. Deficits in immediate working memory were detected in both 10- and 24- to 26-month-old mice. Reference memory deficits and declines in performance in the delayed working memory task were only seen in 24- to 26-month-olds. This increased susceptibility of immediate working memory processes to the aging process in mice may be related to their need for more rehearsal in the water maze than other species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus familiarization effect and the change effect in children's motor task behavior.

After a review of relevant animal and human adult studies, the present paper summarizes 10 experiments using children as Ss and concerned with 2 empirical phenomena: (1) the stimulus familiarization effect (SFE) the tendency for children to respond faster on various motor tasks to a nonfamiliarized as compared with a previously familiarized stimulus; and (2) the change effect (CE) the tendency for children to respond faster on motor task trials involving a change in stimulus from the immediately preceding trial as compared with trials involving repetition of the stimulus occurring on the preceding trial. It is concluded that the SFE is best accounted for by an orientation reaction (OR) habituation assumption, whereas the CE is probably attributable to preexperimentally acquired sets on the part of children to expect stimulus (or response) change as the more apt to occur (or more apt to be required) event in a 2-stimulus, 2-response experimental situation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nitric oxide is involved in the formation of learning and memory in rats: studies using passive avoidance response and Morris water maze task

Blood leukocytes of 16 patients with alcoholic liver cirrhosis and 18 healthy controls were induced for interferon (IFN) production by phytohemagglutinin (PHA) and concanavalin A (ConA) in the presence or absence of isoprinosine and levamisole at concentrations of 10 micrograms/ml and 1 ng/ml. This interferon was neutralized in 87-95% by anti-HuIFN-gamma monoclonal antibodies. In the presence of the drugs the IFN-gamma production was enhanced, however, IFN-gamma titers yielded from leukocytes of cirrhotic patients were still below the titers observed in stimulated and unstimulated blood leukocytes of healthy controls. For example, IFN titers induced by PHA in the presence of levamisole (1 ng/ml) in cirrhotic patients were 2.5 times lower (20.2 +/- 11.1 U/ml) in comparison to healthy subjects (50.6 +/- 27.3 U/ml).     

The task rule congruency effect in task switching reflects activated long-term memory.

Reaction time task rule congruency effects (RT-TRCEs) reflect faster responses to stimuli for which the competing task rules indicate the same correct response than to stimuli indicating conflicting responses. The authors tested the hypothesis that RT-TRCE reflects activated overlearned response category codes in long-term memory (such as up or left). The results support the hypothesis by showing that (a) RT-TRCE was absent for tasks for which there were no response codes ready beforehand, (b) RT-TRCE was present after these tasks were practiced, and (c) these practice effects were found only if the tasks permitted forming abstract response category codes. The increase in the RT-TRCE with response slowness, found only for familiar tasks, suggests that the abstract response category codes may be verbal or linguistic in these cases. The results are discussed in relation to task-switching theories and prefrontal functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posttraining paradoxical sleep in rats is increased after spatial learning in the Morris water maze.

The role of posttraining paradoxical sleep (PS) in spatial or nonspatial learning in the Morris water maze was evaluated. Sprague-Dawley rats were given a 12-trial training session in either the hidden or the visible platform versions of the task. Subgroups then underwent paradoxical sleep deprivation (PSD) beginning at different times after training. Rats with PSD imposed from 14 hr after spatial training had poorer retest scores than any other group. Other rats, implanted with electrodes to permit continuous recording of sleep electroencephalography, were found to undergo a prolonged period of elevated PS after spatial training. By contrast, rats trained in the nonspatial version of the water maze task did not show retention deficits after PSD or elevated PS after training. These results support a role for PS in spatial, but not nonspatial, learning in the Morris water maze. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ipidacrine (NIK-247), a novel antidementia, rapidly enters the brain and improves scopolamine-induced amnesia in rats during the Morris water maze task

The effects of single and repeated administrations of ipidacrine (NIK-247, 9-amino-2, 3, 5, 6, 7, 8-hexahydro-1H-cyclopenta [b] quinoline monohydrochloride monohydrate) on scopolamine-induced spatial learning deficit were investigated in rats using the Morris water maze task. A single oral administration of ipidacrine (0.3 and 1 mg/kg) reduced the increased total latency induced by scopolamine in this task. The repeated administration of ipidacrine (1 mg/kg) of once a day for 5 successive days reduced the increased total latency induced by scopolamine to the levels of the saline-treated control rats in this task. In this pharmaco-kinetic study, ipidacrine was rapidly taken up into the brain within 5 min. Moreover, higher drug levels were observed mainly in the cortex and hippocampus, which both play important roles in learning and memory. Thus, a previous study together with this investigation indicate that ipidacrine improves amnesia which consists of the impairment of the working and reference memory in various animal models, suggesting that ipidacrine is a useful candidate for the therapy of patients with Alzheimer's disease.     

Effects of repeated disorientation on the acquisition of spatial tasks in rats: Dissociation between the appetitive radial arm maze and aversive water maze.

This study examined the effects of disorientation on the acquisition of different spatial reference memory tasks. In an appetitively motivated radial arm maze task in which 1 arm was consistently baited, rats that were disoriented before each trial were impaired in their ability to acquire the task relative to rats placed in a clear container and not disoriented. However, disoriented rats were able to learn a Morris water maze and a water version of the radial arm maze under similar training conditions, suggesting that the effects of disorientation may interact with the quality or quantity of motivation involved in a given task. These results suggest that appetitive and aversive spatial tasks are dissociable, and that any impairment that is due to disorientation is specific to the appetitive radial arm maze task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)