Effects of prenatal exposure to cocaine on Morris water maze performance in adult rats.

The spatial memory of adult rats prenatally exposed to cocaine and that of control offspring was assessed using the Morris water maze. Offspring were derived from Sprague Dawley dams that received subcutaneous injection of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on gestational Days 8-20, pair-fed dams injected with saline, or nontreated control dams. After acquisition, the platform was moved to a new location (reversal phase). Probe trials were conducted at the end of acquisition and reversal training. On the 1st acquisition day, adult male and female offspring prenatally exposed to cocaine required significantly more time and traversed a greater distance to find the hidden platform than did control offspring. Despite these initial differences observed in C40 offspring performance, all of the rats were performing at equivalent levels at the time probe trials were conducted. (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)     

Sex differences in monitoring performance.

220 male and 220 female undergraduates monitored a visual display for 1 hr. Although the results indicate females were poorer monitors, detecting 10% fewer signals and committing more false alarms, these sex differences accounted for only 4% of the variance of detection performance and less than 1% of the variance of the false alarm measure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Traumatic brain injury in the developing rat: effects of maturation on Morris water maze acquisition

Previous work has demonstrated that postnatal and adult rats show different physiological responses to lateral fluid percussion (FP) brain injury. Compared to adult animals, the younger rats showed longer apnea and shorter unconsciousness, and sustained hypotension at all injury severities, with higher mortality following severe traumatic brain injury (TBI). To determine if these younger rats exhibit differential cognitive impairments, the Morris water maze (MWM) was used to compare the degree of spatial learning deficits between moderately injured postnatal day 17 (P17), P28, and adult rats, as well as their age-matched controls. Comparisons between shams of different ages showed a maturational time course for MWM acquisition, where adult rats learned the task 34-58% faster than younger age groups. Injured adults showed escape latency deficits throughout the entire training period, took 39% fewer direct paths to the platform during training, took 24% longer to reach criterion performance, and showed poor probe trial performance than adult shams. Injured P28s exhibited escape latency deficits during the first week, with 23% more trials to criterion and 24% fewer direct paths compared to P28 shams. In contrast, injured P17 rats showed no significant difference from age-matched controls in terms of escape latency, number of direct paths taken, or time to criterion performance. This work suggests that, upon surviving the insult, P17 injured rats show remarkable sparing compared to P28 and adult injured animals.     

Severity of spatial learning impairment in aging: Development of a learning index for performance in the Morris water maze.

The Morris water maze task was originally designed to assess the rat's ability to learn to navigate to a specific location in a relatively large spatial environment. This article describes new measures that provide information about the spatial distribution of the rat's search during both training and probe trial performance. The basic new measure optimizes the use of computer tracking to identify the rat's position with respect to the target location. This proximity measure was found to be highly sensitive to age-related impairment in an assessment of young and aged male Long-Evans rats. Also described is the development of a learning index that provides a continuous, graded measure of the severity of age-related impairment in the task. An index of this type should be useful in correlational analyses with other neurobiological or behavioral measures for the study of individual differences in functional/biological decline in aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in group task performance.

115 female and 118 male psychology students worked individually or in 3-person same-sex groups on a production task (requiring the generation of ideas) or on a discussion task (requiring group members to reach consensus concerning their evaluation of an issue). Because the content of the tasks was carefully selected not to favor the interests or expertise of one sex over the other, no sex differences were expected when Ss worked individually. Results show no gender differences in individual production performance. Only the creativity of the discussion problems was affected by gender; males working individually generated more creative solutions than did females. Consistent with prior research, males in groups generated more solutions to the production problems than did females; females in groups generated higher quality solutions to the discussion problem than did males. (35 ref) (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)     

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)     

Rotation of water in the Morris water maze interferes with path integration mechanisms of place navigation

The idea that place navigation in the Morris water maze is implemented by path integration between locations determined by landmark sighting was investigated in a 200-cm-diameter pool in which circular (7.2 degrees/s) motion of water could be induced by tangentially arranged water jets. The rats were trained at 8 trials per day to navigate to an erectable platform which was raised after the rat had spent a criterion time in the target annulus (30 cm in diameter) in the midpoint of the NW quadrant. Asymptotic escape latency of 7 s was reached after 9 days in moving water (n = 8) and after 6 days in stationary water (n = 8). The group overtrained for 13 days in stable water performed well even after it was transferred to moving water. Changing the sense of rotation of water from counterclockwise to clockwise did not affect the asymptotic performance. The above findings show that overtrained rats rely on landmark sighting rather than on path integration. The influence of water movement reappeared when place navigation to a new target (SW) was examined in alternating 2-s periods of light (L) and darkness (D). On the first day, the latencies were 15.2 +/- 1.2 and 22.8 +/- 1.9 s in stable and moving water, respectively, but dropped to 10 s on the following day. The tracks generated in the L period were more tortuous than those generated in the D period and this difference was more pronounced in moving than in stable water. It is concluded that path integration mechanisms supporting navigation during intervals of darkness are impaired in moving water but that this impairment disappears in overtrained animals.     

Sex differences in the evaluation and performance of dominant acts.

D. Bakan (see PA, Vol 41:2200) conceptualizes 2 major modes of existence: agency and communion. In the agentic (masculine) mode, the individual is concerned with self-protection, self-assertion, and self-enhancement. Communion involves concern with the larger group of which one is a part. Two studies were conducted to explore these distinctions in the domain of dominance. In the 1st, 57 undergraduates evaluated 100 acts, previously and independently nominated as dominant, on their social desirability. Male raters judged self-enhancing and self-asserting acts (e.g., flattering someone to get one's way) as relatively more desirable than did female raters, who judged group-oriented, communal acts (e.g., introducing a speaker at a meeting) as more desirable. In the 2nd study, 83 Ss examined sex differences in the behaviors that express dominance. Dominant men tended to express their dominance through both communal and agentic acts, whereas dominant women tended to express dominance primarily through group-oriented actions. Results lend support to the agency/communion conceptualization and suggest sex-linked differentiation of dominant behavior. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reliability, distribution, and validity of age-related cognitive deficits in the Morris water maze

In the present study, F-344 rats throughout 1.5 to 26 months of age were tested in the reference memory version, a moving-platform repeated acquisition version, and in a cued platform version of the Morris water maze. The results suggest that: (1) performance in the water maze declines continuously, beginning at the earliest age, and very closely fits a linear function; (2) there are robust, reliable differences between individuals in terms of their performance in the Morris water maze, but chronological age accounts for only a fraction of the variance between individuals; (3) there is no evidence of a bimodal distribution among aged rats--there is no distinct subgroup of individuals that performs so poorly that they are qualitatively different from the majority of the population, and distinctions between "impaired" and "unimpaired" subjects must be based on arbitrary criteria that may not be consistent from one study to the next; (4) age-related deficits in the Morris water maze may not be restricted to learning and memory, but may also include deficits in attention, the ability to process spatial information, and/or the ability to develop efficient spatial search strategies; and (5) swim distance is the most appropriate measure of cognitive function in the Morris water maze, but the relationship between this measure and other measures of noncognitive function make it clear that swim distance may not be a pure measure of cognitive function. Although the Morris water maze remains a valuable preclinical test with better validity and specificity than many other behavioral tests, measures of performance in the Morris water maze should not be considered synonymous with cognitive function.     

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)     

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)     

Sex differences in problem-solving performance as a function of attitude differences.

Men make significantly higher scores than women on a scale of attitudes toward problem solving. Attitude scores "have some positive relationship to performance scores." From Psyc Abstracts 36:01:1GD56C. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In vitro autoradiography of hippocampal excitatory amino acid binding in aged Fischer 344 rats: Relationship to performance on the Morris water maze.

Tested young and aged Fischer 344 rats on the place and cue versions of the Morris water maze task. Although all of the young animals reached criterion within the 8-day testing period, the aged animals could be divided into 2 groups on the basis of their performance to criterion: achievers and nonachievers. Upon completion of the water maze testing, the animals were sacrificed, and their brains were processed for in vitro autoradiography of hippocampal excitatory amino acid receptors. Significant differences were found between the young and old rats in the levels of N-methyl-{d}-aspartate, CPP, kainate, and AMPA binding in subregions of the hippocampus. Despite the age-related decline in hippocampal glutamate receptors, no relationship was observed between the density or distribution of excitatory amino acid receptors and performance on the water maze task in the aged rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modafinil and memory: Effects of modafinil on Morris water maze learning and Pavlovian fear conditioning.

Modafinil has been shown to promote wakefulness and some studies suggest the drug can improve cognitive function. Because of many similarities, the mechanism of action may be comparable to classical psychostimulants, although the exact mechanisms of modafinil's actions in wakefulness and cognitive enhancement are unknown. The current study aims to further examine the effects of modafinil as a cognitive enhancer on hippocampus-dependent memory in mice. A high dose of modafinil (75 mg/kg ip) given before training improved acquisition on a Morris water maze. When given only before testing, modafinil did not affect water maze performance. We also examined modafinil (0.075 to 75 mg/kg) on Pavlovian fear conditioning. A low dose of pretraining modafinil (0.75 mg/kg) enhanced memory of contextual fear conditioning (tested off-drug 1 week later) whereas a high dose (75 mg/kg) disrupted memory. Pretraining modafinil did not affect cued conditioning at any dose tested, and immediate posttraining modafinil had no effect on either cued or contextual fear. These results suggest that modafinil's effects of memory are more selective than amphetamine or cocaine and specific to hippocampus-dependent memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aging and atropine effects on spatial navigation in the Morris water task.

A recent animal model that has been particularly useful in the neurobiology of aging has been the age-related decline of spatial information processing capacity in Sprague-Dawley rats measured in the place-learning water task developed by Morris (1981). In the first experiment of the present study, place behavior was examined in young (6 months), old (23–24 months), and very old (28 months) rats of another strain, Long-Evans. As an analogue of aging-related cholinergic dysfunction the effects of atropine sulfate (5–50 mg/kg), an anticholinergic drug that is known to disrupt behavior in this task, also was determined. Place navigation was not impaired in undrugged rats, even those in the oldest age group. Rats treated with atropine showed dose-dependent deficits. In a second experiment, young (4–5 months), old (18–20 months), and very old (28 months) Fischer-344 rats were examined. Place navigation was impaired in the old rats. The very old (28 months) rats could not swim well enough to be tested adequately. Although nonspatial deficits associated with aging may be found across most strains tested, there appear to be very large strain-related differences in spatial processing ability as a function of age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in the connection between need for achievement and school performance.

Hypothesized that in a traditional classroom, only boys of moderate ability and girls of high ability would be strongly motivated to achieve. 138 male and 157 female 7th graders in Norway were tested for need to achieve (n Ach), IQ, and school achievement. Motive to achieve success was measured by the TAT score of n Ach. Results support the hypothesis. It is suggested that bright boys need to be stimulated since they are not inspired to use their motive to achieve and that low-ability boys and low- and average-ability girls are not stimulated to achieve since they probably find the demands too heavy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences and residual effects of food deprivation in the satiated rat.

Following 100 days of food deprivation, during which 9 male and 9 female albino rats received acquisition and extinction training in a runway, and following 2 mo of ad lib feeding, Ss were given a reacquisition test under satiated conditions. Results indicate that females were significantly superior in running speed and frequency of food consumption during satiated reacquisition; while there was a large performance decrement in males following the drive shift, females performed at about the same level during satiation as during food deprivation. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)