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PubMed2005

Testosterone and estradiol produce different effects on cognitive performance in male rats.

The effects of castration and hormone treatment on cognitive performance were evaluated in male rats. Castrated animals received either testosterone or estradiol and were compared with gonadally intact animals and with castrated controls. Results revealed a dissociation between the effects of testosterone and estradiol on cognitive performance in male rats. Specifically, estradiol enhanced acquisition of a delayed matching-to-position spatial task, similar to previously published observations in females. In contrast, neither castration nor testosterone treatment had any significant effect on acquisition of the delayed matching-to-position task, but did appear to affect delay-dependent working memory. None of the treatments had any significant effect on acquisition of a configural association negative patterning task, suggesting that effects on the delayed matching-to-position task were not due to effects on motivational factors. These data demonstrate that, as in females, gonadal hormones influence cognitive performance in males and suggest that estradiol and testosterone affect distinct cognitive domains.

Analysis of Variance↗
PubMed2005

Effects of pregnancy on spatial cognition in female Hooded Long-Evans rats.

Studies examining the roles of estrogens and progestins on spatial cognition have been highly contradictory. To determine if the hormonal environment of pregnancy affects spatial cognition, pregnant (n = 7) and virgin (n = 7) Hooded Long-Evans rats were tested in a Morris water maze throughout the 3 weeks of pregnancy and the second week postpartum. Latency to platform, path length, swim velocity, and time in quadrant were compared over trial-days. To compare water maze performance with changes in hormone levels, serum concentrations of estradiol and progesterone were measured on the first, third, and fifth days of testing during the third week of pregnancy. Subjects learned to find the platform as indicated by decreased time and distance to platform over each trial-week and increased time spent in the quadrant where the platform had been located the previous week. However, there were no differences between treatment groups on time or distance to platform over trial-days. Swim velocity did not differ between or within groups over the 4 weeks of testing. Although primigravid and virgin females were similar in their abilities to learn the novel location of a submerged platform and return to it over time, pregnant animals demonstrated less perseveration to previously learned information and were quicker to locate the platform when it moved to a new location. Thus, reproductive status did not affect reference memory but enhanced working memory in the Morris water maze.

Analysis of Variance↗
PubMed2005

Testosterone modulates performance on a spatial working memory task in male rats.

Gonadal hormones have been shown to modulate memory retention in female rats. The current experiments examine the role of testicular hormones in modulating the performance of male rats on two spatial water maze tasks. In the first study, castrated and intact rats were trained on the visible platform and hidden platform versions of the Morris water maze task. Castration did not affect performance on either version of this reference memory task with castrated and intact rats demonstrating similar performance both during acquisition and on post-training probe trials. In the second experiment, castrated and intact rats were tested on a delayed-matching-to-place version of the water maze. Rats received a series of trial pairs in the maze with a hidden platform located in the same pool location on the exposure and retention trials of each pair; between pairs of trials, however, the platform was repositioned to a novel pool location. The interval between trials was either 10- or 60-min and memory retention, taken as the difference between the pathlengths on the exposure and retention trials, declined as the interval increased. Relative to intact males, castrated males demonstrated impaired working memory retention at 60-min but not at 10-min retention intervals. This interval-dependent impairment in working memory retention was reversed by physiologic levels of testosterone replacement. These findings indicate that castration does not significantly affect acquisition or probe trial performance on a classic reference memory task but does impair spatial working memory retention, an effect that is reversed by exogenous testosterone.

Analysis of Variance↗
PubMed2006

Chronic 17beta-estradiol pretreatment and ischemia-induced hippocampal degeneration and memory impairments: a 6-month survival study.

Exogenous administration of estrogen has been shown to significantly reduce ischemia-induced neuronal degeneration. However, the long-term impact of such treatment on neuronal protection and functional recovery remain largely unknown. The present study assessed the effects of a 15-day pretreatment with 17beta-estradiol on memory deficits and neuronal damage up to 6 months following a 10-min global ischemia in rats. Four groups of ovariectomized female rats [sham-operated and ischemic rats receiving a 15-day pretreatment of either the vehicle or 17beta-estradiol (100 microg/kg)] were tested. The 8-arm radial maze and object recognition tests served to evaluate the impact of 17beta-estradiol treatment on ischemia-induced spatial and recognition memory impairments, respectively. Testing in the radial maze was initiated at two distinct time intervals following reperfusion (7 and 120 days) to evaluate changes in memory functions over time. Our findings revealed long-lasting neuroprotective effects of 17beta-estradiol treatment on hippocampal CA1 pyramidal cells in ovariectomized ischemic rats (43.5% greater neuronal survival than observed in vehicle-treated ischemic animals). Importantly, this neuronal protection translated into significant improvements of recognition and spatial memory functions in estradiol-treated ischemic rats.

Analysis of Variance↗
PubMed2006

Impairment of spatial learning by estradiol treatment in female mice is attenuated by estradiol exposure during development.

High doses of estradiol (E(2)) can impair spatial learning in the Morris water maze, in ovariectomized mice, but the same dose has no effect on adult castrated males. Here, we test the hypothesis that this sex difference is caused by neonatal actions of E(2). In Experiment 1, C57BL/6J pups were given daily estradiol benzoate (EB) or oil injections from the day of birth until postnatal Day 3. Adults were gonadectomized and received EB (s.c.) or oil 28 h before the first day of training, and 4 h before each of four daily training sessions on the Morris water maze. Females given oil as neonates, and EB prior to training displayed the poorest performance. Females that received EB as neonates and EB prior to training were insensitive to the deleterious effects of adult EB and performed better than males given the same hormone treatments. We conducted a second experiment using aromatase enzyme knockout (ArKO) mice. Adult male and female ArKO and wild-type (WT) littermates were gonadectomized and received either injections of oil or EB prior to and during water maze training (as described above). Hormone treatment failed to affect performance, yet, female but not male ArKO mice showed impaired learning compared to WT littermates. Thus, exposure to estradiol during neonatal development can counteract the deleterious effects of EB on adult spatial learning.

Animals↗
PubMed2006

The effect of intrahippocampal insulin microinjection on spatial learning and memory.

Insulin is best known for its action on peripheral target tissues such as the adipocyte, muscle and liver to regulate glucose homeostasis. Insulin and its receptor are found in specific area of CNS with a variety of region-specific functions different from its direct glucose regulation in the periphery. The hippocampus and cerebral cortex distributed insulin/insulin receptor has been shown to be involved in brain cognitive functions. Previous studies about the effect of insulin on memory are controversial. In the present study, the effect of insulin microinjection into CA1 region of rat hippocampus on water maze performance has been investigated. Insulin had a discrepant effect dose dependently. The spatial learning and memory were impaired with lower dose of insulin, had not changed with intermediate doses, while they improved with higher doses. These results suggest that insulin may have a dose-dependent effect on spatial learning and memory.

Animals↗
PubMed2003

The impact of hands-free message reception/response on driving task performance.

A series of closed-course driving experiments were conducted in which 41 drivers ranging in age from 19 to 70 were put through a series of increasingly challenging driving performance tasks both in the presence and absence of audible messages. The messages required specific responses and these, along with driving performance measures based on driver/vehicle response characteristics, were recorded. The results clearly showed a negative impact of the message task on driver decision-making performance when this involved the more complex tasks of weaving and especially left-turning. Such decision-making decrements in the presence of the messages were exacerbated by adverse pavement surface conditions.

Adult↗
PubMed2004

An accident waiting to happen: a spatial approach to proactive pedestrian planning.

There are about 75,000 pedestrian crashes in the United States each year. Approximately 5000 of these crashes are fatal, accounting for 12% of all roadway deaths. On college campuses, pedestrian exposure and crash-risk can be quite high. Therefore, we analyzed pedestrian crashes on the campus of the University of North Carolina at Chapel Hill (UNC) as a test case for our spatially-oriented prototype tool that combines perceived-risk (survey) data with police-reported crash data to obtain a more complete picture of pedestrian crash-risk. We use spatial analysis techniques combined with regression models to understand factors associated with risk. The spatial analysis is based on comparing two distributions, i.e. the locations of perceived-risk with police-reported crash locations. The differences between the two distributions are statistically significant, implying that certain locations on campus are perceived as dangerous, though pedestrian crashes have not yet occurred there, and there are actual locations of police-reported crashes that are not perceived to be dangerous by pedestrians or drivers. Furthermore, we estimate negative binomial regression models to combine pedestrian and automobile exposure with roadway characteristics and spatial/land use information. The models show that high exposure, incomplete sidewalks and high crosswalk density are associated with greater observed and perceived pedestrian crash-risk. Additionally, we found that people perceive a lower risk near university libraries, stadiums, and academic buildings, despite the occurrence of crashes.

Accidents, Traffic↗
PubMed2002

Attending to objects: costs or benefits?

The single-object advantage is said to occur when performance is faster and/or more accurate when the two targets to be compared appear on one object than when they appear on two different objects. The single-object advantage has been interpreted to suggest that attention can select objects rather than unparsed regions of visual space. In five experiments we explored whether directing attention to one object rather than two objects produces a benefit or a minor cost. Participants were required to compare two target features that belonged to one object, to two objects, or did not belong to any object. In addition, we varied the relevance to the task of object-related global information, such as symmetry of the object and perceptual cluttering of the background. Results showed that attending to one object in comparison to attending to no object produced a benefit only when object-related global information was relevant to the task. In contrast, when object-related global information was irrelevant to the task, attending to one object produced a cost. Thus, it can be concluded that attending to an object does not produce an absolute benefit, but rather produces a smaller cost than attending to two objects.

Attention↗
PubMed2003

Exocentric pointing to opposite targets.

We use an exocentric pointing task to study exocentric visual directions to targets that are opposite to a pointer relative to the observer. (The apparent distance between the target and the pointer always exceeded 90 degrees of visual angle.) All pointing takes place in the horizontal plane at eye height. Observers could not see both target and pointer at a single glance. They had to look back and forth between them, using combinations of eye movements, head turns, twists at the waist and turning on the feet. In the limit of diametrically opposite targets we find that the observers pick either one of two distinct orientations of the pointer as equally "visually correct". Which one results depends on the stance assumed by the observer. The difference between the two equally acceptable pointings is between 5 degrees and 10 degrees. Such a result is predicted from earlier measurements in the context of a model that describes the geometry of the horizon as a Riemannian space with varying intrinsic curvature. The present results thus fit--perhaps surprisingly--very well in such a picture.

Eye Movements↗
PubMed1996

Visual-spatial deficits expalin visual symptoms in Alzheimer's disease.

PURPOSE: To determine whether the visual symptoms of patients with Alzheimer's disease are related to visual-spatial dysfunction. METHODS: We administered a test battery modified from existing neuropsychometric materials that taxed visual-spatial skills, form identification, color vision, and visual memory. We tested 14 patients with Alzheimer's disease who had visual symptoms prominent enough to prompt ophthalmologic consultation, 11 patients with Alzheimer's disease who lacked such visual symptoms, and a control group of 53 subjects without Alzheimer's disease. The groups with Alzheimer's disease were matched for Wechsler Adult Intelligence Scale-Revised scores. RESULTS: Patients with Alzheimer's disease who had prominent visual symptoms differed significantly from those without prominent visual symptoms only in their relatively poor visual-spatial test scores. CONCLUSIONS: Visual symptoms in Alzheimer's disease are related primarily to visual-spatial deficits. These findings are consistent with previous evidence that patients with Alzheimer's disease who have prominent visual symptoms have accentuated histologic and metabolic abnormalities in the parieto-occipital regions known to process visual-spatial information. The findings support the view that pathways mediating visual-spatial and form identification are at least partially segregated in the brain, and emphasize that tests used to screen visually symptomatic patients with Alzheimer's disease will be more effective if they prominently assess visual-spatial skills.

Aged↗
PubMed1976

Communication and spatial relationships in a colony of common grackles.

Most communication among common grackles Quiscalus quiscula occurs at distances of less than a few metres in the noisy environment of a breeding colony. This report examines both the adaptations of communication to these conditions and the effects of communication in regulating individual's spatial relationships. For each of six vocalizations and five action patterns studied in one colony, I consider variation in the form of the display, the circumstances associated with its use, and the responses it elicits. Each individual, male or female, has one characteristic, stereotyped song pattern that would facilitate individual recognition between mates. Variation in the components of vocalizations and action patterns is of two kinds: unidimensional, with either covarying or nested components, or multidimensional, with independently varying components, alternatives that have different implications for communication. The wide-spectrum sounds made by common grackles offer advantages in close-range communication in colonies, because the ease of locating such signals would minimize the cocktail-party effect, although they would have disadvantages in long-range communication. Most vocalizations of common grackles lack assocations with specific responses or external contexts, a situation that should often characterize short-range communication between acquainted individuals. The responses to vocalizations vary with context, especially the initial spatial relationships and identities of the interactors.

Animal Communication↗
PubMed2003

Spatial working memory as an endophenotype for schizophrenia.

BACKGROUND: Spatial working memory impairments are among the neurocognitive deficits that may mark genetic predisposition toward schizophrenia. We previously reported that impairment on the spatial span subtask of the Wechsler Adult Intelligence Scale-Revised increased in a dose-dependent manner with increasing genetic predisposition toward schizophrenia in a sample of discordant twins; however, it remains to be determined whether these deficits reflect difficulties with encoding, maintenance, manipulation, time-tagging of visual spatial information, storage capacity, or complex motor response. METHODS: We developed a spatial delayed response task in which memory set size was parametrically varied, holding constant manipulation and decision processes. We then reassessed 80 of the previously studied twins (17 probands with 8 monozygotic co-twins and 13 dizygotic co-twins, and 42 healthy twins). RESULTS: The spatial delayed response task was sensitive to genetic loading for schizophrenia but did not provide evidence for capacity limitations in probands or their co-twins. CONCLUSIONS: The findings suggest that deficits in the encoding or storage aspects of short-term spatial mnemonic processing may be an effective endophenotypic marker for schizophrenia.

Female↗
PubMed1999

Local infusion of an alpha-1 adrenergic agonist into the prefrontal cortex impairs spatial working memory performance in monkeys.

BACKGROUND: Stimulation of alpha-2 adrenoceptors in the monkey or rat prefrontal cortex (PFC) has been known to improve spatial working memory (SWM) and stimulation of alpha-1 adrenoceptors in the rat PFC has been reported to impair SWM. The present study attempted to replicate in monkey the rat experiments on alpha-1 adrenoceptor stimulation. METHODS: The alpha-1 adrenergic agonist phenylephrine or the alpha-2 adrenergic agonist guanfacine was infused into the dorsolateral prefrontal cortex (dlPFC) of monkeys performing the delayed-response (DR) task, a task of SWM, to see how the drugs affect SWM performance. RESULTS: Phenylephrine infusion in dlPFC significantly impaired DR performance, whereas guanfacine improved performance. The effects of both drugs were delay-dependent. Infusions outside dlPFC were ineffective. CONCLUSIONS: Stimulation of prefrontal cortical alpha-1 adrenoceptors impairs SWM function in monkeys, consistent with the parallel study in rats, whereas stimulation of alpha-2 adrenoceptors improves SWM, indicating that alpha-1 and alpha-2 adrenoceptors may have opposing roles in the PFC.

Adrenergic alpha-1 Receptor Agonists↗
PubMed2000

Disturbance of rat lever-press learning by hippocampo-prefrontal disconnection.

To determine whether the medial prefrontal cortex (PFC), ventral hippocampus and hippocampo-PFC pathway are involved in operant lever-press learning, we conducted lidocaine injections to these brain sites. Rats were injected immediately after lever-press acquisition in the first training, and the second 5-min test the next day. Results showed the response rate of either PFC- or ventral hippocampus-inactivated rats to be lower than that of control rats in the test the next day. Rats having lidocaine injected into the unilateral ventral hippocampus combined with contralateral medial PFC also showed lower response rate in their tests. These results suggest that hippocampo-PFC disconnection disturbs operant learning.

Animals↗