ACQUISITION AND REVERSAL OF DISCRIMINATIONS IN MALNOURISHED RATS

Abstract

A nutritional deficiency often results in multiple morphological, neurochemical and behavioral consequences. This experiment analyzed the acquisition and reversal in a discrimination learning task in control and early malnourished independent groups of rats with light or sound as discriminative stimuli. The animals received diets with 16% (Controls- C) or 6% of protein (Malnourished – M) from birth to 35 days of life. After this period, animals received commercial diet ad libitum until the end of the experiment (recovery period for malnourished group). Before day 85 of life, preparing for the discrimination training, the body weight was reduced in 15% of the ad libitum weight. During acquisition of the discrimination bar presses were reinforced with water in RV 12:1 during the SD (Light or Sound) and extinguished during stimuli removal. After an 80% discrimination index was reached, a reversal phase was initiated in which responding was reinforced during the absence light or sound. Both groups showed a significant session effect in both phases. The malnourished discrimination performance was similar to the control animals, and there was no significant effect of diet or stimulus modality. The comparison of the rate of responding between the acquisition and reversal phases showed more significant differences in SD than in SD (the animals maintained the rate of responding during the old S?) and a tendency of better performance during the light SD than with the sound SD. However, there were no significant differences between malnourished and control groups. These data suggest that a refinement in procedures is necessary in order to identify more subtle changes in the discrimination learning due to early malnutrition.Key words: protein malnutrition, discrimination learning, discrimination reversal, sound, light, bar press, rats