Hunger and satiety determine foraging decissions in land snails: Evidence from the invasive species Theba pisana.

The foraging behaviour of gastropod molluscs usually involves complex decisions that provide a model for the study of high-order cognitive processes. Land snails tested for food-finding in the laboratory, however, have shown an invariable feeding pattern: novel foods are mostly missed (i.e. just found by chance) whilst familiar foods, due to a type of conditioned attraction, are always located and ingested. This effect, known as Food-attraction conditioning, has led to the conclusion that, regardless of their hunger level, land snails are both willing to eat anything at any moment and also blind to the odours of novel foods. An alternative account of these findings emerges from the fact that the snails are usually tested whilst in a moderate state of hunger, so that they benefit from feeding on known foods but not from taking the risk of feeding on those that are unknown. The present experiments suggest that it is the case. Snails of the invasive species Theba pisana were tested for food-finding according to their seasonal cycle in a laboratory located in their native Mediterranean region. Subjects collected at the beginning of their aestivation period succeed in locating novel food items after being deprived for a long period (45 days), but ignored a conditioned food when they were sated with this food at the end of their lethargy. The results allow us to conclude that the feeding behaviour of snails is the product of a complex cost-benefit analysis in which their motivational state and the stimuli they perceive (and the memory of such stimuli), are evaluated. Finally, we anticipate that these results will be of use in increasing the efficiency of current baits employed for the protection of crops.

Individual differences in chemotherapy-induced anticipatory nausea.

Anticipatory Nausea (AN) is a severe side effect of chemotherapy that can lead cancer patients to discontinue their treatment. This kind of nausea is usually elicited by the re-exposure of the patients to the clinical context they need to attend to be treated. There has been considerable agreement that AN represents a paradigmatic example of Pavlovian conditioning, and within this framework, several behavioral interventions have been proposed in order to prevent this phenomenon. However, some studies have questioned the validity of the Pavlovian approach, suggesting that CS-US associations are neither necessary nor sufficient for AN to occur. The data and the alternative theories behind such criticisms are discussed. Additionally, it is suggested that animal models of AN could be enriched by taking into account rats' individual differences.

Fluid consumption in lithium-treated rats: roles of stimulus novelty and context novelty.

In 5 experiments thirsty rats received an injection of lithium chloride or of saline, and their consumption of fluid was monitored at 5-min intervals for 30 min. The novelty of the fluid and the novelty of the test context was varied. In Experiment 1 a novel fluid (a sucrose solution) was offered in a novel context; in Experiment 2 the fluid was novel and the context was familiar (the home cage); in Experiment 3 the fluid was familiar and the context was novel; and in Experiment 4 both fluid and context were familiar. Lithium influenced fluid consumption in those designs that included at least one novel feature (Experiments 1, 2, and 3, but not in Experiment 4). Consumption was initially enhanced (with respect to the controls) when the context was novel, but was suppressed when the fluid was novel. In Experiment 5, the flavor was over-ingested after lithium treatment when it was presented in a short (5 min) test conducted in a novel place, but was rejected in a subsequent consumption in the home cages. It is argued that the effect of lithium depends on two factors: enhanced attention to salient cues that modifies the exploratory responses evoked by a novel context; rapid conditioning of an aversion when the fluid consumed is novel. Implications for the use of fluid consumption as an index of lithium-induced nausea are considered.

Fracturas crecedoras del cráneo en la infancia / Growing skull fractures in childhood

Presentamos 7 casos operados de fractura crecedora de cráneo. El desgarro dural es un hecho fundamental en el desarrollo de esta condición. Se enfatiza la importancia del cierre dural meticuloso como hecho central del tratamiento quirúrgico. Destacamos la importancia del seguimiento clínico-radiológico de los lactantes y pre-escolares portadores de una fractura lineal de cráneo