Preadaptation to the feeding schedule does not eliminate activity-based anorexia in rats

To test whether activity-based anorexia (ABA) still occurs after preadaptation to the feeding schedule, 20 rats were first exposed to a feeding schedule of one 90-min meal per day until adaptation occurred (measured by maintenance of stable body weight). Then, during ABA training, half the rats (wheel group) were confined in running wheels except during the daily meal, and half (cage group) were not. Wheel running suppressed feeding—that is, food intake in the wheel group was less than that in the cage group. Also, the rats in the wheel group lost weight, whereas those in the cage group did not. Wheel running increased over days. Thus, the defining characteristics of ABA were evident in rats that were not subjected to ABA training until after they had become well adapted to the feeding schedule. These findings support the view that the suppression of feeding produced by wheel running triggers the vicious circle of ABA. They also cast doubt on the hypothesis that activity-induced interference with adaptation to the feeding schedule plays a key role in causing ABA.     

Function learning: induction of continuous stimulus-response relations.

This research investigates how people learn to select particular response magnitudes along one physical dimension (duration) when given stimulus magnitudes from another dimension (spatial extent). Stimuli and correct responses were related by either a power function, a logarithmic function, or a linear function with a positive intercept. The power function was learned quickly and accurately. In contrast, systematic response biases occurred during the early phases of learning the logarithmic and linear functions. As practice progressed, however, the biases gradually disappeared. These results support an adaptive regression model. According to it, people learn functions through a subjective process analogous to statistical regression. There is assumed to be an initial constraint that treats stimulus-response pairs as if a power function characterizes them.