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At least 613 records · Page 34Linked to original sources
PubMed2004

Memantine improves spatial learning in a transgenic mouse model of Alzheimer's disease.

Memantine, a low- to moderate-affinity uncompetitive N-methyl-D-aspartate receptor antagonist, has been shown to improve learning and memory in several pharmacological models of Alzheimer's disease (AD). In the present study, the effect of memantine on locomotor activity, social behavior, and spatial learning was assessed in a transgenic mouse model of AD. Eight-month-old male C57BL/6J mice carrying mutated human APP and PS1 genes (APP/PS1) and their nontransgenic (NT) litter mates were administered a therapeutic dose of memantine (30 mg/kg/day p.o.) for 2 to 3 weeks. At this age, APP/PS1 mice show elevated levels of beta-amyloid peptides in several brain regions. APP/PS1 mice exhibited less exploratory rearing and increased aggressive behavior compared with NT mice. In the water maze test for spatial learning, APP/PS1 mice had longer escape latencies to both hidden and visible platforms, but they did not differ from NT mice in their swimming speed. Memantine significantly improved the acquisition of the water maze in APP/PS1 mice without affecting swimming speed. Memantine did not affect either locomotor activity or aggressive behavior in either genotype. These data indicate that memantine improves hippocampus-based spatial learning in a transgenic mouse model of AD without producing nonspecific effects on locomotion/exploratory activity.

Aggression↗
PubMed1994

Thymectomy-induced deterioration of learning and memory in mice.

Male ddY mice were thymectomized 4 weeks after birth. Learning behaviors, tested in passive and active avoidance performances and in a spatial memory task, were significantly impaired in thymectomized mice at 10 months after thymectomy, in addition to the reduced immune response. Contents of hypothalamic norepinephrine and hypothalamic choline acetyltransferase activity were significantly increased in thymectomized mice. These results suggested that thymectomy at young adult life in mice not only impaired the immune response, but also deteriorated the learning and memory ability.

Animals↗
PubMed2007

Spatial bridges and the spread of Chlamydia: the case of a county in Sweden.

OBJECTIVES: The so-called small-world effect can have a great impact on efforts to control the incidence and prevalence of sexually transmitted infections. This is because a small number of so-called spatial bridgers (individuals who, through sexual contacts, interconnect geographically distant areas) can drastically lower the average path length in the sexual network and, as a result, make locally based intervention programs much less effective. The objectives of this study were to analyze the sociodemographic characteristics of these bridgers and to compare the result with the remaining study population. The purpose was to determine whether it is possible to identify them for targeted intervention programs. STUDY DESIGN: During 2001, contact tracing was performed in approximately 98% of all cases with positive test results in Värmland County. The sexual networks obtained constituted a study population of 851 individuals. Statistical analysis was used to characterize individuals engaged in spatial bridging behavior. RESULTS: Approximately 8% of the study population was characterized as spatial bridgers. Using multivariate analysis, we found almost no significant differences between these individuals and the rest of the study population when it came to sociodemographic variables, including education, economy, and ethnicity. CONCLUSION: The number of spatial bridgers is high enough to create a small-world network with links that can fuel the endemic chlamydia in Värmland County. Sociodemographic information could not be used to characterize spatial bridgers. In interventions against chlamydia, spatial bridgers shall be considered as potentially important for sustaining the disease.

Adolescent↗
PubMed1994

Interaction between 5-HT1A and nicotinic cholinergic receptors in the regulation of water maze navigation behavior.

The interaction between serotonin (5-HT)1A and nicotinic cholinergic receptors in the regulation of spatial navigation behavior in the Morris water maze (WM) test was studied. Pretraining intraperitoneal (i.p.) injections of a combination of subthreshold doses of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (a 5-HT1A receptor agonist) at 30 micrograms/kg and mecamylamine (a nicotinic cholinergic receptor antagonist) a 2500 micrograms/kg greatly impaired WM navigation to a hidden platform and slightly, but not statistically significantly, impaired WM navigation to a visible platform. Post-training i.p. injections of this combination had no effect on WM navigation performance. Serotonin depletion induced by p-chlorophenylalanine (PCPA) increased the performance impairing action of pretraining injected combination of 8-OH-DPAT 30 micrograms/kg and mecamylamine 2500 micrograms/kg. In trained rats combined injections of 8-OH-DPAT 30 micrograms/kg and mecamylamine 2500 micrograms/kg given pretraining had no effect on the navigation to a hidden platform located in a familiar or in a novel position. Pretraining trial injected combination of hexamethonium 2000 micrograms/kg (a peripherally acting nicotinic antagonist) and 8-OH-DPAT 30 micrograms/kg had no effect on navigation. These data suggest that a combined treatment with a 5-HT1a receptor agonist and a nicotinic cholinergic receptor antagonist more severely impair non-mnemonic acquisition performance processes than consolidation and retrieval processes.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2003

Effects of subconvulsive electrical stimulation to the hippocampus on emotionality and spatial learning and memory in rats.

OBJECTIVE: To observe the effects of repeated subconvulsive electrical stimuli to the hippocampus on the emotional behavior and spatial learning and memory ability in rats. METHODS: One hundred and eight male Wistar rats were randomized into 3 groups. Animals in group SE (n = 42) were given subconvulsive electrical stimulation to the hippocampus through a constant pulsating current of 100 mu A with an intratrain frequency of 25 Hz, pulse duration of 1 millisecond, train duration of 10 seconds and interstimulus interval of 7 minutes, 8 times a day, for 5 days. In the electrode control group or CE group (n = 33), animals were implanted with an electrode in the hippocampus, but were not stimulated. Group NC (n = 33) animals received no electrode or any stimulation. The emotional behavior of experimental rats was examined by activity in an unfamiliar open field and resistance to capture from the open field, while the spatial learning and memory ability was measured during training in a Morris water maze. RESULTS: The stimulated rats tested 1 month after the last round of stimulation displayed substantial decreases in open field activity (scale: 10.4 +/- 2.3, P < 0.05) and increases in resistance to capture (scale: 2.85 +/- 0.56, P < 0.01). The amount of time for rats in group SE to find the platform (latency) as a measurement for spatial bias was prolonged (29 +/- 7) seconds after 15 trials in the water maze, P < 0.05). The experimental rats swam aimlessly in all four pool quadrants during the probe trial in the Morris water maze. CONCLUSIONS: Following repeated subconvulsive electrical stimuli to the hippocampus, rats displayed long-lasting significant abnormalities in emotional behavior, increased anxiety and defensiveness, enhanced ease to and delayed habituation to startlement, transitory spatial learning and memory disorder, which parallels many of the symptoms in posttraumatic stress disorder patients.

Animals↗
PubMed2006

Minimum-norm reconstruction for sensitivity-encoded magnetic resonance spectroscopic imaging.

In this work we propose minimum-norm reconstruction as a means to enhance the spatial response behavior in parallel spectroscopic MRI. By directly optimizing the shape of the spatial response function (SRF), the new method accounts for coil sensitivity variation across individual voxels and their side lobes. In this fashion, it mitigates the signal contamination and side-lobe aliasing, to which previous techniques are susceptible at low resolution. Although the computational burden is higher, minimum-norm reconstruction is shown to be feasible using an iterative algorithm. Benefits in terms of SRF shape and artifact suppression are demonstrated.

Algorithms↗
PubMed2001

The approximately ideal, more or less free distribution.

We present the minimum set of requirements necessary and sufficient to represent the foraging behaviour of an animal, and its utilisation of food, in order to explore the emergent properties of behaviour that allow animals to reduce their hunger. We present an individual-based model of foraging that provides a simple quantification of the requirements, which is sufficiently simple to yield some analytical results. Complex interactions beyond the scope of analysis have been explored through simulating animals foraging in regenerating patchy environments. In most cases the populations pass into equilibrium distributions which appear to be stable. The equilibria always approximate closely to the ideal free distribution, although typically with a small degree of undermatching. (Undermatching is the term applied to the departure from the ideal free distribution caused by a smaller proportion of the population than expected occupying areas with a higher than average regeneration rate). The model therefore implies that the distribution, hitherto accounted for in terms of ESSs may, in fact, be simply an effect of the animal's utilization of the food it collects to reduce its hunger. The model defines a specific feeling rate, v, the rate at which an animal can feed on a unit of food. This is a function of three parameters, v1, the specific feeding rate when alone, v(infinity), the rate, possibly zero, at which it can feed in the presence of an indefinitely large number of conspecifics, and n1/2, the number of conspecifics that cause v to take the value (v1+v(infinity)/2. Exploitation competition in the absence of interference is represented by setting v1 = v(infinity). Differences in competitive ability in exploitation have been represented by simulating animals with a range of values of v1, those with the larger values, feeding more rapidly, being the more effective competitors, and those with the lower values being the less effective. Interference competition is represented by setting v1 > v(infinity) and social facilitation by v1 < v(infinity). Individual differences in the strength of interaction are represented by different values of n(1/2). In competition, the animals with the larger values of n(1/2) are the more effective competitors: in facilitation, they are the less effective facilitators. The addition of physiological and behavioural detail makes very little alteration to the emergent equilibria, always close to the ideal free distribution, almost always showing undermatching.

Animals↗
PubMed2006

Individual and sex differences in learning abilities of ravens.

Behavioral and physiological characteristics of individuals within the same species have been found to be stable across time and contexts. In this study, we investigated individual differences in learning abilities and object and social manipulation to test for consistency within individuals across different tasks. Individual ravens (Corvus corax) were tested in simple color and position discrimination tasks to establish their learning abilities. We found that males were significantly better in the acquisition of the first discrimination task and the object manipulation task, but not in any of the other tasks. Furthermore, faster learners engaged less often in manipulations of conspecifics and exploration of objects to get access to food. No relationship between object and social manipulation and reversal training were found. Our results suggest that individual differences in regard to the acquisition of new tasks may be related to personalities or at least object manipulation in ravens.

Animals↗
PubMed2006

Population coding strategies and involvement of the superior colliculus in the tactile orienting behavior of naked mole-rats.

Even simple behaviors of vertebrates are typically generated by the concerted action of large numbers of brain cells. However, the mechanisms by which groups of neurons work together as functional populations to guide behavior remain largely unknown. One of the major model systems for exploring these mechanisms has been mammalian visuomotor behavior. We describe here experiments that establish a new model system for analyzing the sensory control of behavior by neuronal populations using a mammalian somatosensory response: orientation to touch cues in a rodent. We found that the CNS mechanisms used to direct these orientation responses to touch can be delineated from behavioral experiments. In this study we demonstrate that the superior colliculus, a component of the vertebrate midbrain most often thought of as a visual structure, is an essential component of the naked mole-rat's unique tactile orienting behavior. Furthermore, the information processing that underlies this behavior displays striking parallels with that used for visual orientation at anatomical and computational levels.

Animals↗
PubMed1999

Molecular mechanisms of Fyn-tyrosine kinase for regulating mammalian behaviors and ethanol sensitivity.

Mice lacking Fyn, a Src-related non-receptor tyrosine kinase, show impairment of various behaviors, such as spatial learning, suckling, emotional behaviors, and ethanol sensitivity. These mice also display both morphological defects and impairment of synaptic function. Fyn is highly expressed in the mammalian CNS from embryonic day 8.5 to adulthood. Pharmacological and electrophysiological analyses of mice lacking Fyn reveal gamma-aminobutyric acid and glutamatergic defects. We propose here the hypothesis that these defects are caused separately by developmental disorganization and impairment of synapse function by a deficit in Fyn. Regarding the glutamatergic defect, in particular, after ethanol administration the N-methyl-D-aspartate (NMDA)-dependent function is recovered by Fyn, paralleled with tyrosine phosphorylation of NMDA receptor 2B subtype. Thus, modulation of the NMDA receptor function by Fyn may have a significant role in building and regulating sophisticated neural circuits and behavior. In addition, the cadherin-related neural receptor (CNR) family is isolated by binding activity for Fyn. The CNR-Fyn complex will also open a new angle for gaining insight into the molecular mechanisms for regulating mammalian behavior.

Affective Symptoms↗
PubMed2003

Open-field behavior withstands drastic changes in arena size.

Individual voles were tested on successive days under increasing, decreasing, or randomly changing arena size. Locomotor behavior was adjusted to arena size by (i) preserving the same level of activity, (ii) taking longer but less frequent trips in smaller arenas in contrast to taking more frequent yet shorter trips in the larger arenas, and (iii) moving in the entire space available for exploration in the smaller arenas in contrast to remaining along the walls of the open field in the larger arenas. The effect of testing order was minimal, probably being related to increased novelty under increasing arena size, as opposed to habituation under decreasing arena size, when parts of the same area were re-explored. These behavioral changes averaged up to a two-fold difference compared with the larger six-fold change in the perimeter and 44-fold change in the area of the open field. The modest change in open-field behavior indicates that it has a solid spatio-temporal structure that withstands extensive environmental changes. This behavioral stability and consistency further validates studies of pharmacological, neurological, and genetic preparations that use behavior in a small open field as representation of the general pattern of behavior.

Animals↗
PubMed2001

Dissociation of the effects of bilateral lesions of the dorsal hippocampus and parietal cortex on path integration in the rat.

Rodents are able to rely on self-motion (idiothetic) cues and navigate toward a reference place by path integration. The authors tested the effects of dorsal hippocampal and parietal lesions in a homing task to dissociate the respective roles of the hippocampus and the parietal cortex in path integration. Hippocampal rats exhibited a strong deficit in learning the basic task. Parietal rats displayed a performance impairment as a function of the complexity of their outward paths when the food was placed at varying locations. These results suggest that the parietal cortex plays a specific role in path integration and in the processing of idiothetic information, whereas the hippocampus is involved in the calibration of space used by the path integration system.

Animals↗
PubMed2005

Do humans integrate routes into a cognitive map? Map- versus landmark-based navigation of novel shortcuts.

Do humans integrate experience on specific routes into metric survey knowledge of the environment, or do they depend on a simpler strategy of landmark navigation? The authors tested this question using a novel shortcut paradigm during walking in a virtual environment. The authors find that participants could not take successful shortcuts in a desert world but could do so with dispersed landmarks in a forest. On catch trials, participants were drawn toward the displaced landmarks whether the landmarks were clustered near the target location or along the shortcut route. However, when landmarks appeared unreliable, participants fell back on coarse survey knowledge. Like honeybees (F. C. Dyer, 1991), humans do not appear to derive accurate cognitive maps from path integration to guide navigation but, instead, depend on landmarks when they are available.

Adolescent↗
PubMed1996

Defective imitation of gestures in patients with damage in the left or right hemispheres.

OBJECTIVES: Defective imitation of meaningless gestures has repeatedly been demonstrated in patients with apraxia and has been interpreted as being due to a deficit of motor execution. There is, however, controversy as to whether some impairment of imitation also occurs in patients with right brain damage. The aim was to compare defective imitation in patients with left and right brain damage and to explore whether there are qualitative differences between them. METHODS: Imitation was examined in 80 patients with left brain damage (LBD) and aphasia, 40 patients with right brain damage (RBD), and 60 controls for three types of gestures:hand positions, finger configurations, and combined gestures which required a defined hand position as well as a defined configuration of the fingers. RESULTS: Regardless of whether imitation of hand positions and finger configurations were tested each on their own or together, they showed differential susceptibility to RBD and LBD. Whereas imitation of finger configurations was about equally impaired in RBD and LBD, defective imitation of hand positions occurred almost exclusively in patients with LBD, and whereas controls as well as patients with RBD committed less errors with hand positions than with finger configurations, the reverse was the case in patients with LBD. CONCLUSIONS: The pattern of results goes against a deficit of motor execution as being the cause of defective imitation in patients with LBD, as it is difficult to see why such a deficit should affect proximal movements necessary for reaching hand positions more than differential finger movements. An alternative explanation would be that in patients with LBD errors are due to defective mediation by knowledge about the human body whereas in patients with RBD they stem from faulty visuospatial analysis of the demonstrated gesture.

Adult↗
PubMed1978

Development of behavior in Lemur macaco in the first nineteen weeks.

Eight young Lemur macaco were observed in a zoo during the first 19 weeks of life. Data were obtained on general motor development, development of independence from the mother, contributions of mothers and young to thhe maintenance of proximity, nursing, grooming, relations between twins, play, feeding, sexual dichromatism, and communication. The results are compared with similar data from other prosimians and from anthropoid primates, and some suggestions made about the evolutionary and adaptive significance of certain aspects of L. macaco development.

Agonistic Behavior↗