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Age-dependent pathways of brain energy metabolism: the suckling rat, a natural model of the ketogenic diet.

As a consequence of the high fat content of maternal milk, the suckling rat may be viewed as a 'natural model' of the ketogenic diet. Changes in energy metabolism during this period of development may give us some clues into the antiepileptic properties of the ketogenic diet. We have, therefore studied the postnatal evolution of local cerebral metabolic rates for glucose (LCMRglcs) and of regional rates of cerebral uptake of beta-hydroxybutyrate (betaHB) in the developing rat between postnatal day (PN) 10 and 35. LCMRglcs were low and homogeneous at PN10. They increased significantly in four auditory regions between PN10 and PN14, at the time of maturation of auditory function. Between PN14 and PN17, they increased further in two auditory regions, one visual area (the lateral geniculate nucleus), three limbic and three motor areas. These increases occurred simultaneously with the maturation of vision and the development of locomotion and general exploratory behavior. Between PN17 and PN21, LCMRglcs increased by 28-97% (depending on brain area) and by a mean value of 25% in all areas studied. In contrast to the function-related increases in LCMRglcs, regional rates of cerebral betaHB uptake underwent a generalized non-specific increase between PN1O and PN14, and stayed at a high level until PN17. Between PN17 and PN21, rates of cerebral betaHB uptake decreased significantly in all brain regions studied, and reached very low levels by PN35. Thus, even in the suckling rat, whose cerebral metabolic activity depends upon both glucose and ketone bodies, it is the postnatal increases in LCMRglcs that appear to be critical for the acquisition of new functions and neurological competence. Conversely, the homogeneous increase in cerebral betaHB uptake occurring between PN10 and PN17 at a period of active brain growth may rather reflect non-specific mechanisms of cell growth.

3-Hydroxybutyric Acid↗

Acute stress enhances anxiolytic-like drug responses of mice tested in a black and white test box.

Drug-induced facilitation of exploration of a two-compartment black and white test box was studied in mice applying different stressors before test. Tail suspension suppressed exploration of both compartments and enhanced diazepam- or eltoprazine-induced increase of exploration of the white compartment. (-)-Penbutolol reversed the effects of eltoprazine suggesting involvement of 5-HT(1A/1B) receptors. Buspirone had weak effects both under standard conditions, and after tail suspension. Ritanserin suppressed exploratory behavior, and this effect was potentiated by tail suspension. In conclusion, application of acute tail suspension stress immediately before test in the black and white box enhanced the sensitivity to drugs. In contrast to this, forced swimming suppressed general behavioral activity, but in this case diazepam facilitated the behavior in both compartments. Foot shocks immediately before test reduced activity in the black compartment and did not affect the behavior in the white compartment. Thus different acute stressors modified behavior in the black and white box differently. Chronic stress (crowded housing) produced an anxiolytic-like response.

Animals↗

Calibration of vector navigation in desert ants.

Desert ants (Cataglyphis sp.) monitor their position relative to the nest using a form of dead reckoning [1] [2] [3] known as path integration (PI) [4]. They do this with a sun compass and an odometer to update an accumulator that records their current position [1]. Ants can use PI to return to the nest [2] [3]. Here, we report that desert ants, like honeybees [5] and hamsters [6], can also use PI to approach a previously visited food source. To navigate to a goal using only PI information, a forager must recall a previous state of the accumulator specifying the goal, and compare it with the accumulator's current state [4]. The comparison - essentially vector subtraction - gives the direction to the goal. This whole process, which we call vector navigation, was found to be calibrated at recognised sites, such as the nest and a familiar feeder, throughout the life of a forager. If a forager was trained around a one-way circuit in which the result of PI on the return route did not match the result on the outward route, calibration caused the ant's trajectories to be misdirected. We propose a model of vector navigation to suggest how calibration could produce such trajectories.

Animals↗

Brain function and personality in normal males: a SPECT study using statistical parametric mapping.

Understanding the differences between individuals' personality types at a functional brain level is now possible due to recent developments in both functional brain imaging and personality models. The psychobiological model for temperament and character offers one approach to exploring personality. This study uses SPECT imaging to investigate brain function in relationship to the personality traits in the Temperament and Character Index. A general linear model approach was implemented at a voxel-by-voxel level, using quartile groupings for the personality predictors. t contrasts were used to investigate significant clusters of activation or deactivation. The results show a number of significant relationships between personality traits and regional cerebral blood flow, which show distinct nonlinear trends. All seven of the Cloninger personality traits were significantly related to regional cerebral blood flow. The results suggest that differences in brain function in some regions may reflect differences in personality traits.

Adult↗

Children's preference for challenge: the role of perceived competence and control.

This research tested the hypothesis that children's perceptions of academic competence and their personal control over school-related performance affects subsequent intrinsic interest and preference for challenge in an evaluative setting. In a correlational study, children's self-reported perceptions of academic competence and personal control were found to relate positively to their intrinsic interest in schoolwork and preference for challenging school activities. A subset of this sample was exposed to varying levels of a controlling directive, and preference for challenge was assessed behaviorally during a free-choice period in which subjects were unaware that they were being observed. As predicted, the data indicated that when given the evaluative, controlling directive, children who had high perceptions of academic competence and control preferred a greater challenge than did children whose perceptions were low on these measures. No difference between groups in terms of preference for challenge was evident when no controlling directive was presented. These findings are discussed in terms of theories of intrinsic motivation and potential processes that underly these effects.

Achievement↗

Enhancing the expression of flavor neophobia: some effects of the ingestion-illness contingency.

Four experiments investigating factors contributing to enhanced ingestional neophobia are reported. Rats administered lithium chloride following ingestion of a novel coffee solution showed an enhanced neophobia reaction to vinegar and casein. This enhancement was specific to the novelty of both the conditioning and test fluids and was not observed in animals receiving noncontingent toxicosis. Poisoning alone, however, mediated a nonspecific fluid suppression that persisted for approximately two drinking sessions following treatment. In contrast to other experiments, the operation of generalization was detected only when a novel flavor was the test fluid, suggesting that neophobia enhancement is at least partially mediated by a conditioned novelty aversion resulting from the novel flavor-lithium contingency.

Animals↗

Psychosocial correlates and predictors of AIDS risk behaviors, abortion, and drug use among a community sample, of young adult women.

Relations among latent constructs of Social Conformity, Sensation Seeking, Polydrug Use, Sexual Experience, Abortion, and Risky AIDS Behaviors were examined among a community sample of women (N = 438, mean age = 25.5 years) using confirmatory factor analysis (CFA) and predictive structural equation models (SEM). In the CFA, Risky AIDS Behavior was strongly related to more Polydrug Use and less Social Conformity and modestly related to Sexual Experience and Abortions. In SEMs, Social Conformity significantly predicted less Risky AIDS Behavior and less Polydrug Use but did not predict Abortions. Prior Sexual Experience predicted more Polydrug Use and Abortions. We conclude that the same psychological processes and predispositions that relate low social conformity to drug use and other unhealthy behaviors also influence AIDS-risk behaviors, even among a community sample of women.

Abortion, Induced↗

Radio-frequency lesions of the thalamus produce delayed-nonmatching-to-sample impairments comparable to pyrithiamine-induced encephalopathy in rats.

Rats were trained and matched on a delayed-nonmatching-to-sample (DNMTS) task and randomly assigned to treatment. In Experiment 1, radio-frequency (RF) lesions were aimed at lateral portions of the internal medullary lamina (L-IML), midline thalamus (MT), mammillary bodies (MB), and the combination of MT and MB. In Experiment 2, RF lesions were aimed at the fornix. After recovery, DNMTS was retrained at retention intervals retention interval of 3.0-18.0 s, the critical retention interval for 75% DNMTS accuracy was determined by a staircase procedure, and spontaneous exploration was observed in an open field. L-IML lesions produced significant deficits on DNMTS and exploratory behavior that were comparable to deficits on the same tasks in rats recovered from pyrithiamine-induced thiamine deficiency. Fornix lesions produced significant DNMTS deficits that were substantially smaller than for the L-IML group. The MT, MB, and MT+MB treatments had no significant effect on DNMTS.

Alcohol Amnestic Disorder↗

Attitude formation through exploration: valence asymmetries.

The formation of attitudes toward novel objects was examined as a function of exploratory behavior. An initial experiment, in which participants played a computer game that required them to learn which stimuli, when sampled, produced favorable or unfavorable outcomes, demonstrated learning, attitude formation, and generalization to novel objects. The findings also revealed 2 interesting valence asymmetries: a learning asymmetry involving better learning for negatively valenced than positively valenced objects and a generalization asymmetry involving stronger generalization as a function of negative than of positive attitudes. Findings from 4 experiments led to an explanation of the learning asymmetry in terms of information gain being contingent on approach behavior and related the generalization asymmetry to a negativity bias that weighs resemblance to a known negative more heavily than resemblance to a positive.

Adult↗

Imitation of the sequential structure of actions by chimpanzees (Pan troglodytes).

Imitation was studied experimentally by allowing chimpanzees (Pan troglodytes) to observe alternative patterns of actions for opening a specially designed "artificial fruit." Like problematic foods primates deal with naturally, with the test fruit several defenses had to be removed to gain access to an edible core, but the sequential order and method of defense removal could be systematically varied. Each subject repeatedly observed 1 of 2 alternative techniques for removing each defense and 1 of 2 alternative sequential patterns of defense removal. Imitation of sequential organization emerged after repeated cycles of demonstration and attempts at opening the fruit. Imitation in chimpanzees may thus have some power to produce cultural convergence, counter to the supposition that individual learning processes corrupt copied actions. Imitation of sequential organization was accompanied by imitation of some aspects of the techniques that made up the sequence.

Animals↗

Does Octopus vulgaris have preferred arms?

Previous behavioral studies in Octopus vulgaris revealed lateralization of eye use. In this study, the authors expanded the scope to investigate arm preferences. The octopus's generalist hunting lifestyle and the structure of their arms suggest that these animals have no need to designate specific arms for specific tasks. However, octopuses also show behaviors, like exploration, in which only single or small groups of arms are involved. Here the authors show that octopuses had a strong preference for anterior arm use to reach for and explore objects, which points toward a task division between anterior and posterior arms. Four out of 8 subjects also showed a lateral bias. In addition, octopuses had a preference for a specific arm to reach into a T maze to retrieve a food reward. These findings give evidence for limb-specialization in an animal whose 8 arms were believed to be equipotential.

Animals↗

Neonatal amygdala lesions affect appetitive motivational and consummatory aspects of social behavior in the rat.

In the present study, rats received amygdala lesions (AMX) on either Postnatal Day 7 (PD 7; immature brain) or PD 21 (almost mature brain), and adult social activity was studied after short-term isolation housing. Sham-operated rats demonstrated increased following and approaching behavior after 7 days of isolation compared with after 4 days of isolation, an effect that was absent in AMX-PD 7 and AMX-PD 21 rats. Furthermore, AMX-PD 7 rats, but not AMX-PD 21 rats, displayed a reduction in investigatory behavior after prolonged isolation. This indicates that in AMX-PD 21 rats, mainly appetitive motivational aspects of social behavior were affected, whereas in AMX-PD 7 rats both motivational and consummatory aspects were disturbed. Finally, the reported deficits in AMX-PD 7 rats may reflect neurodevelopmental deficits of structures connected with the amygdala.

Age Factors↗

Polycose taste pre-exposure fails to influence behavioral and neural indices of taste novelty.

Taste novelty can strongly modulate the speed and efficacy of taste aversion learning. Novel sweet tastes enhance c-Fos-like immunoreactivity (FLI) in the central amygdala and insular cortex. The present studies examined whether this neural correlate of novelty extends to different taste types by measuring FLI signals after exposure to novel and familiar polysaccharide (Polycose) and salt (NaCl) tastes. Novel Polycose not only failed to elevate FLI expression in central amygdala and insular cortex, but also failed to induce stronger taste aversion learning than familiar Polycose. Novel NaCl, on the other hand, showed patterns of FLI activation and aversion learning similar to that of novel sweet tastes. Possible reasons for the resistance of Polycose to typical pre-exposure effects are discussed.

Analysis of Variance↗