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At least 523 records · Page 29Linked to original sources
PubMed2000

DNA fragmentation factor 45 deficient mice exhibit enhanced spatial learning and memory compared to wild-type control mice.

Programmed cell death or apoptosis is a highly regulated physiological process that is critical in development, particularly in the central nervous system. The DNA fragmentation factor 45 (DFF45 or ICAD) is a subunit of a heterodimeric DNase complex that is crucial for DNA fragmentation and normal apoptosis. To examine the neurobiological consequences of lacking DNA fragmentation and timely apoptosis during mouse development in vivo, we compared spatial learning behaviors in DFF45 mutant and wild-type control mice. We found that DFF45 mutant mice exhibit enhanced spatial learning and memory compared to wild-type mice. Moreover, both the granule cell density and total granule cell number in the hippocampal dentate gyrus region are higher in the DFF45 mutant brains than in the wild-type brains. We propose that the increase in granule cell number in the dentate region due to the DFF45 mutation changes the neuronal network underlying spatial learning and memory in DFF45 mutant mice.

Animals↗
PubMed1987

Transitive movements in a deafferented man.

It has not been determined if the performance of transitive movement requires sensory feedback from the limb to the brain. We tested a deafferented patient's ability to pantomime, imitate, and use actual objects in both eyes open and eyes closed conditions. Although his performance deteriorated when his eyes were closed, the major error made by this patient was the inability to correctly orient the instrument (or pretended instrument) toward the object of the instrument's action.

Adult↗
PubMed1996

A simple computer based system to analyze Morris water maze trials on-line.

The development of a system for the acquisition, analysis and storage of data from open-field water-maze procedures in which rats learn to escape from water onto a hidden platform is described. The use of an object-oriented programming language simplifies the programming of the application and provides scientists without formal training in computer programming the ability to create their own software application. The core hardware is an IBM-compatible AT 486 computer and a video capture board. The Microsoft Windows compatible software is written in G (LabVIEW) and presents the user a graphically based 'virtual instrument' thus simulating functions of real instruments which can be interactively accessed. The graphical approach allows the programmer to make fast and simple adaptations of the software to suit the specific experimental problem. Image analysis software tools (Concept V.i) were integrated into this system which has been used successfully for over 2 years in our lab.

Animals↗
PubMed1976

Ranks and relationships in Highland ponies and Highland Cows.

Recent studies of primates have questioned the importance of dominance hierarchies in groups living under natural conditions. In a herd of Highland ponies and one of Highland cattle grazing under free-range conditions on the Isle of Rhum (Inner Hebrides) well defined hierarchies were present. The provision of food produced a marked increase in the frequency of agonistic interactions but had no effect on the rank systems of the two herds. While rank was clearly important in affecting the distribution of agonistic interactions, it was poorly related to behaviour in non-agonistic situations.

Agonistic Behavior↗
PubMed2002

Landmark use and development of navigation behaviour in the weakly electric fish Gnathonemus petersii (Mormyridae; Teleostei).

African mormyrids, such as Gnathonemus petersii, migrate: nocturnally, from daytime shelters to find food and return by morning, and seasonally, spawning in swamps flooded during the rainy season. The present study examined whether the fish use landmarks detected via electrolocation to locate an aperture, whether they detect changes in landmark size and respond appropriately, whether landmarks or hydrostatic pressure are the primary cues for navigation and whether fish of different developmental stages behave differently with respect to landmarks and navigation. The fish's task was to locate and swim through a circular aperture in a wall dividing an aquarium into two compartments. Two groups of fish were trained to find the aperture with a landmark present, while a control group had no such landmark. The water level remained constant throughout training. At the end of training, the fish's task was to locate the aperture after the landmark size had changed or the water level had increased. The results show that G. petersii use landmarks to orient and navigate. They can detect changes in landmark size and will modify their locomotor behaviour to integrate the change into an internal representation. If the water level changes, increasing hydrostatic pressure, the fish orient to a landmark, if present. If no landmark is present, the fish rely on an internal representation oriented to hydrostatic pressure. Larger, early-adult G. petersii located the aperture faster than smaller, sub-adult fish.

Animals↗
PubMed2003

Reasoning, models, and images: behavioral measures and cortical activity.

The goal of this study was to investigate the neurocognitive processes of mental imagery in deductive reasoning. Behavioral studies yielded four sorts of verbal relations: (1) visuospatial relations that are easy to envisage both visually and spatially; (2) visual relations that are easy to envisage visually but hard to envisage spatially; (3) spatial relations that are hard to envisage visually but easy to envisage spatially; and (4) control relations that are hard to envisage both visually and spatially. In three experiments, visual relations slowed the process of reasoning in comparison with control relations, whereas visuospatial and spatial relations yielded inferences comparable to those of control relations. An experiment using functional magnetic resonance imaging showed that in the absence of any correlated visual input (problems were presented acoustically via headphones), all types of reasoning problems evoked activity in the left middle temporal gyrus, in the right superior parietal cortex, and bilaterally in the precuneus. In the prefrontal cortex, increased activity was found in the middle and inferior frontal gyri. However, only the problems based on visual relations also activated areas of the visual association cortex corresponding to V2. The results indicate that cortical activity during reasoning depends on the nature of verbal relations. All relations elicit mental models that underlie reasoning, but visual relations in addition elicit visual images. This account resolves inconsistencies in the previous literature.

Acoustic Stimulation↗
PubMed1999

Behavioral effects of ivermectin in mice.

BACKGROUND AND PURPOSE: Ivermectin is a common anthelmintic drug, widely used in laboratory rodents for treatment of pinworm and mite infestations. We evaluated the action of ivermectin on sensitive behavioral tasks in mice during treatment for mites within a barrier facility. METHODS: A total of 21 (5 males, 16 females) mice (129/SvEv) were used for measuring body weight, open field locomotor activity, and rotarod motor coordination. For acoustic startle and prepulse inhibition, 20 C57BL/6J and 29 AKR/J mice were studied. For the Morris water task, the same 20 C57BL/6J mice were studied. Ivermectin (0.08% sheep drench) was administered in the drinking water of the home cage for 8 weeks. Control groups received normal tap water in identical bottles. RESULTS: Ivermectin did not affect general health, body weight, motor coordination, swimming behavior, or spatial learning in several inbred strains of mice. However, it induced a small but significant effect on some sensitive behaviors. CONCLUSIONS: A cautious approach to initiating ivermectin treatment in mice should be used for sensitive behavioral experiments.

Acoustic Stimulation↗
PubMed1982

Laboratory observations of aggregative behavior of garter snakes, Thamnophis sirtalis: roles of the visual, olfactory, and vomeronasal senses.

Two experiments were conducted to determine (a) whether male garter snakes (Thamnophis sirtalis) require a functional vomeronasal or olfactory system to return to previously preferred shelter locations and (b) the sensory modalities used by snakes to aggregate in the absence of previously deposited chemical cues. In Experiment 1, snakes with vomeronasal nerve lesions did not return to previously preferred shelter locations when tested individually. However, when tested with a group that included "control" animals, they returned to previously preferred shelters. The shelter-selection behavior of snakes with olfactory nerve lesions improved postoperatively, whereas the behavior of animals with sham lesions was unchanged. In Experiment 2, snakes were tested for aggregation in aquaria in which the substrate and other contents were cleaned between trials. After blindfolding or after olfactory nerve cuts, snakes aggregated at normal levels. When the snakes' vomeronasal ducts were sutured closed, aggregation scores were significantly depressed, although two of the three groups with vomeronasal duct sutures did aggregate just above chance levels. These studies indicate that use of chemical signals by garter snakes in shelter selection and aggregation is mediated by the vomeronasal system and that neither the olfactory nor the visual system is critical for these behaviors.

Animals↗
PubMed2002

The impact of consumer-resource cycles on the coexistence of competing consumers.

This article seeks to determine the extent to which endogenous consumer-resource cycles can contribute to the coexistence of competing consumer species. It begins with a numerical analysis of a simple model proposed by Armstrong and McGehee. This model has a single resource and two consumers, one with a linear functional response and one with a saturating response. Coexistence of the two consumer species can occur when the species with a saturating response generates population cycles of the resource, and also has a lower resource requirement for zero population growth. Coexistence can be achieved over a wide range of relative efficiencies of the two consumers provided that the functional response of the saturating consumer reaches its half-saturation value when the resource population is a small fraction of its carrying capacity. In this case, the range of efficiencies allowing coexistence is comparable to that when two competitors have stable dynamics and a high degree of resource partitioning. A variety of modifications of this basic model are analyzed to investigate the consequences for coexistence of different resource growth equations, different functional and numerical response shapes, and other factors. Large differences in functional response shape appear to be the most important factor in producing robust coexistence via resource cycles. If the unstable species has a concave numerical response, this greatly expands the conditions allowing coexistence. If the stable consumer species has a convex (accelerating) functional and/or numerical response, the range of conditions allowing coexistence is also expanded. We argue that large between-species differences in functional response form can often be produced by between-consumer differences in the adaptive adjustments of foraging effort to food density. Consumer-resource cycles can also expand the conditions allowing coexistence when there is resource partitioning, but do so primarily when resource partitioning is relatively slight; this makes the ease of coexistence relatively independent of consumer similarity.

Ecosystem↗
PubMed2003

The well-worn route and the path less traveled: distinct neural bases of route following and wayfinding in humans.

Finding one's way in a large-scale environment may engage different cognitive processes than following a familiar route. The neural bases of these processes were investigated using functional MRI (fMRI). Subjects found their way in one virtual-reality town and followed a well-learned route in another. In a control condition, subjects followed a visible trail. Within subjects, accurate wayfinding activated the right posterior hippocampus. Between-subjects correlations with performance showed that good navigators (i.e., accurate wayfinders) activated the anterior hippocampus during wayfinding and head of caudate during route following. These results coincide with neurophysiological evidence for distinct response (caudate) and place (hippocampal) representations supporting navigation. We argue that the type of representation used influences both performance and concomitant fMRI activation patterns.

Adult↗