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A study of orientation in a zero gravity environment by means of virtual reality simulation.

When the International Space Station (ISS) is completed and starts its operation, crew members will be stationed for three months or more in orbit aboard the ISS. As they stay longer in the space environment, "habitability" for them will become most important in the design of the interior space. One of the problems about habitability in a zero gravity (0 G) environment is disorientation. Crew members have difficulty in discriminating between "up" and "down" and more serious disorientations may cause space motion sickness. Crew members rely on visual perception to orient themselves because they can't use their sense of equilibrium in a 0 G environment. Although color and the direction of equipment of Space Shuttles or modules has been considered, no systematic study has been conducted on interior space. This study intended to clarify how people acquire visual information and recognize their orientation in a 0 G environment by an experiment in which a subject wears a head-mounted display (HMD) and enters a virtual weightless state represented by computer graphics (CG). Visual information of a room and the degree-of-freedom of motion were varied to examine the influence of the conditions on such a simple task as movement through several connected modules, and the performance and the behavior of each subject were investigated.

Humans↗

Ocular dominance column width and contrast sensitivity in monkeys reared with strabismus or anisometropia.

PURPOSE: To study the relationship between the width of ocular dominance columns in primary visual cortex and spatial contrast sensitivity functions in monkeys with strabismus or anisometropia during infancy. METHODS: Adult monkeys having had monocular visual abnormalities induced in infancy were tested behaviorally for spatial contrast sensitivity and then subjected to functional enucleation of one eye to reveal the ocular dominance columns (ODCs) of the primary visual cortex by cytochrome oxidase (CO) staining. The relative widths of the left and right eyes' ODCs were measured and related to the contrast sensitivity functions. RESULTS: The relative widths of the ODCs having input from eyes with strabismic or anisometropic amblyopia were reduced in proportion to the age of onset and the duration of the early visual abnormality. The relative losses in contrast sensitivity were in ordinal agreement with the losses in relative width of the ODCs. CONCLUSIONS: Amblyopia induced by the early monocular abnormalities of strabismus or anisometropia is proportional to the loss in cortical afference as reflected in the reduction in width of the respective ODCs in the primary visual cortex.

Amblyopia↗

Anxiety and increased 5-HT1A receptor response in NCAM null mutant mice.

Mice deficient in the neural cell adhesion molecule (NCAM) show behavioral abnormalities as adults, including altered exploratory behavior, deficits in spatial learning, and increased intermale aggression. Here, we report increased anxiety-like behavior of homozygous (NCAM-/-) and heterozygous (NCAM/-) mutant mice in a light/dark avoidance test, independent of genetic background and gender. Anxiety-like behavior was reduced in both NCAM+/+ and NCAM-/- mice by systemic administration of the benzodiazepine agonist diazepam and the 5-HT1A receptor agonists buspirone and 8-OH-DPAT. However, NCAM-/- mice showed anxiolytic-like effects at lower doses of buspirone and 8-OH-DPAT than NCAM+/+ mice. Such increased response to 5-HT1A receptor stimulation suggests a functional change in the serotonergic system of NCAM-/- mice, likely involved in the control of anxiety and aggression. However, 5-HT1A receptor binding and tissue content of serotonin and its metabolite 5-hydroxyindolacetic acid were found unaltered in every brain area of NCAM-/- mice investigated, indicating that expression of 5-HT1A receptors as well as synthesis and release of serotonin are largely unchanged in NCAM-/- mice. We hypothesize a critical involvement of endogenous NCAM in serotonergic transmission via 5-HT1A receptors and inwardly rectifying K+ channels as the respective effector systems.

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

Learned interaction of visual and idiothetic cues in the control of place field orientation.

In a symmetrical environment (like a square box) hippocampal place cells use a mixture of visual and idiothetic (movement) information to tell them which way the environment is oriented. The present experiment tested the hypothesis that if the visual landmarks were mobile, place cells would learn to disregard these and rely on idiothetic cues instead. Place cells were recorded in a square box surrounded by circular black curtains. A cue card hung on the curtain behind one of the walls to break the fourfold symmetry. The relative influence of this card on the location of place fields was assessed each day by confining the rat on a rotating platter underneath an opaque cover, and then rotating the card and the platter by different amounts, to see whether subsequently recorded place fields had rotated with the card or with the rat. For some rats, these trials had been preceded by trials in which the card had been visibly moved from trial to trial, so that the rats had seen that it was mobile. Other rats received no prior visual information that the card was mobile. In the rats that had previously seen the card move, place fields initially rotated with the card but by the end of five sessions usually rotated with the rat instead. For rats that had never seen the card move, place fields always followed the card. Thus, the cells were able to "learn" that their preferred directional input, the card, was unreliable. A third group of rats, who were covered only for 30 s while the card was moved, showed mixed behaviour, suggesting a degradation of the idiothetic trace with time.

Animals↗

Striatal microinjections of interleukin-2 and rat behaviour in the elevated plus-maze.

We showed that the relationship between cytokine mRNA in the rat brain and elevated plus-maze behaviour is site- (striatum, prefrontal cortex), and cytokine-specific (interleukin-2). Here, we investigated whether a striatal microinjection of interleukin-2 (1, 10, 25 ng) affects elevated plus-maze behaviour. Analyses showed no acute effects of IL-2 on open arm time, whereas dose-dependent differences in rearing activity, and open arm entries became apparent between IL-2 doses. Twenty-four hours later, a previous dose of 25 ng IL-2 showed a trend for more open arm time compared to vehicle. These behavioural changes are discussed in relation to anxiety-relevant and exploratory behaviour, and possible neurochemical mechanisms.

Analysis of Variance↗

Behavior of the gray short-tailed opossum (Monodelphis domestica) in the open field and in response to a new object, in comparison with the rat.

We compared the behavior of the gray short-tailed opossums (Monodelphis domestica) and Long-Evans rats during repeated exposures to the open-field (OF) test. Animals were videotaped for 10 min on four consecutive days. A new object was placed in the center of the field on the third day and it was present there again on the fourth day. The rate of locomotor activity in the opossum was always higher than that in the rat. On the first exposure to the open field, both species showed strong thigmotaxy. On the second day, opossums shifted a significant part of their activity to the internal and central parts of the field, while thigmotaxy dominated in the rats' behavior till the end of the experiment. The frequency and time of exploration of a new object placed on the central square was higher in the opossums than in rats. They also showed higher frequency of rearings and lower defecation scores, while the time of grooming was similar to the rats'. These results, that are consistent with those of our earlier experiments in the elevated plus maze (EPM), show that in response to novelty Monodelphis opossums change their behavior from defensive to exploratory faster than rats and then explore it more intensely. These differences may be either a result of different ecologies or evolution of the two species.

Animals↗

Non-random patterns of host use by the different parasite species exploiting a cockle population.

Different parasite species sharing the same intermediate host species may have similar or conflicting interests, depending on whether they are at the same stage in their life-cycle or whether they share the same definitive host. In the New Zealand cockle, Austrovenus stutchburyi, metacercariae of the digenean Meiogymnophallus sp. are positively associated with metacercariae of Curtuteria australis. This relationship is found in different cockle samples, and is independent of cockle shell size, which suggests that it is not merely the product of metacercariae accumulation over time. Both digenean species have the same definitive host, oystercatchers. Metacercariae of C. australis manipulate the phenotype of cockles, impairing the cockle's ability to burrow in the sediments. This makes the host more susceptible to oystercatcher predation. Thus Meiogymnophallus sp. can benefit by associating with C. australis and may hitch a ride with the manipulator parasite. This is supported by the finding that cockles impaired by C. australis and lying at the sediment surface harbour greater numbers of Meiogymnophallus than buried cockles. A third digenean species, whose sporocysts are found in cockles and which is not transmitted by predation, occurred only in surface cockles. Finally, a parasitic copepod with a direct life-cycle was found evenly distributed among buried and surface cockles, independently of their metacercarial loads. These results show that different parasite species do not use cockles in a random fashion, and that not all patterns of host use are consistent with shared or conflicting interests among parasites.

Animals↗

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.

Animals↗

Transthyretin is involved in depression-like behaviour and exploratory activity.

Transthyretin (TTR), the major transporter of thyroid hormones and vitamin A in cerebrospinal fluid (CSF), binds the Alzheimer beta-peptide and thus might confer protection against neurodegeneration. In addition, altered TTR levels have been described in the CSF of patients with psychiatric disorders, yet its function in the CNS is far from understood. To determine the role of TTR in behaviour we evaluated the performance of TTR-null mice in standardized tasks described to assess depression, exploratory activity and anxiety. We show that the absence of TTR is associated with increased exploratory activity and reduced signs of depressive-like behaviour. In order to investigate the mechanism underlying these alterations, we measured the levels of catecholamines. We found that the levels of noradrenaline were significantly increased in the limbic forebrain of TTR-null mice. This report represents the first clear indication that TTR plays a role in behaviour, probably by modulation of the noradrenergic system.

Animals↗

Selecting the best home range model: an information-theoretic approach.

Choosing an appropriate home range model is important for describing space use by animals and understanding the ecological processes affecting animal movement. Traditional approaches for choosing among home range models have not resulted in general, consistent, and unambiguous criteria that can be applied to individual data sets. We present a new application of information-theoretic model selection that overcomes many of the limitations of traditional approaches, as follows. (1) It alleviates the need to know the true home range to assess home range models, thus allowing performance to be evaluated with data on individual animals. (2) The best model can be chosen from a set of candidate models with the proper balance between fit and complexity. (3) If candidate home range models are based on underlying ecological processes, researchers can use the selected model not only to describe the home range, but also to infer the importance of various ecological processes affecting animal movements within the home range.

Animal Migration↗