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BackgroundBrain regions that mediate learning of a conditioned place preference (CPP) undergo significant development in pre and periadolescence. Consuming a high fat (HF) diet during this developmental period and into adulthood can lead to learning impairments in rodents. The present study tested whether HF diet intake, consumed only in pre and periadolescence, would be sufficient to cause impairments using a CPP procedure.MethodsRats were randomly assigned to consume a HF or a low fat (LF) diet during postnatal days (PD) 21-40 and were then placed back on a standard lab chow diet. A 20-day CPP procedure, using HF Cheetos® as the unconditioned stimulus (US), began either the next day (PD 41) or 40 days later (PD 81). A separate group of adult rats were given the HF diet for 20 days beginning on PD 61, and then immediately underwent the 20-day CPP procedure beginning on PD 81.ResultsPre and periadolescent exposure to a LF diet or adult exposure to a HF diet did not interfere with the development of a HF food-induced CPP, as these groups exhibited robust preferences for the HF Cheetos® food-paired compartment. However, pre and periadolescent exposure to the HF diet impaired the development of a HF food-induced CPP regardless of whether it was assessed immediately or 40 days after the exposure to the HF diet, and despite showing increased consumption of the HF Cheetos® in conditioning.ConclusionsIntake of a HF diet, consumed only in pre and periadolescence, has long-lasting effects on learning that persist into adulthood.

The hypothesis that participants will eat more fruits (apple slices) and vegetables (carrot cuts) if they are made more proximate and visible was tested using a 2 × 2 between-participants design. Proximity was manipulated by placing fruits and vegetables in a bowl at a table where participants sat (near) or 2 m from the table (far). Visibility was manipulated by placing fruits and vegetables in an opaque bowl that was covered (not visible) or in a clear bowl that was open (visible). The results showed that placing apple slices and carrot cuts in closer proximity to participants increased intake of these healthy foods. Making these foods more visible increased intake of apple slices but not carrot cuts, possibly because fruits taste sweet and so may be more motivationally salient than bitter-tasting carrots. Regardless, these data are the first to demonstrate experimentally that the proximity and visibility of fruits and vegetables can influence intake of these foods.