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Prenatal protein malnutrition and hippocampal function: partial reinforcement extinction effect
J Tonkiss1, G A Foster, J R Galler
1Center for Behavioral Development and Mental Retardation, Boston University School of Medicine, MA 02118.
Insights
Prenatal malnutrition did not affect the partial reinforcement extinction effect (PREE) in rats, showing similar persistence in both malnourished and control groups. However, prenatal nutrition influenced running speed during acquisition, suggesting altered food motivation.
Area of Science:
- Behavioral neuroscience
- Nutritional science
- Animal behavior
Background:
- Prenatal nutrition is critical for neurodevelopment and can influence long-term behavioral outcomes.
- Malnutrition during development may impact learning, motivation, and response persistence.
- The partial reinforcement extinction effect (PREE) is a robust phenomenon demonstrating increased persistence after intermittent reward schedules.
Purpose of the Study:
- To investigate the impact of prenatal protein malnutrition on the partial reinforcement extinction effect (PREE) in rats.
- To examine how prenatal nutrition affects instrumental learning and motivation.
- To determine if prenatal malnutrition alters response persistence during extinction after continuous or partial reinforcement.
Main Methods:
- Rats were fed low (6% casein) or adequate (25% casein) protein diets during gestation.
- Offspring were subjected to food restriction to 80% of free-feeding weight.
- Animals were trained to run for food rewards under continuous reinforcement (CR) or partial reinforcement (PR) schedules, followed by extinction trials.
Main Results:
- A significant partial reinforcement extinction effect (PREE) was observed in both previously malnourished and control rats, with PR groups showing greater persistence than CR groups.
- Differences in running speed were noted during acquisition between malnourished and control groups under both CR and PR conditions.
- These acquisition differences suggest that prenatal malnutrition may affect food motivation.
Conclusions:
- Prenatal protein malnutrition does not abolish the partial reinforcement extinction effect (PREE).
- Behavioral persistence during extinction is preserved despite prenatal nutritional insults.
- Prenatal malnutrition can influence instrumental learning acquisition, potentially through altered motivational states.
Abstract:
Developing rats were either malnourished or well-nourished during the prenatal period by feeding their dams diets of low (6% casein) or adequate (25% casein) protein content 5 weeks prior to mating and throughout pregnancy. All pups were well-nourished from the day of birth onwards. Male offspring aged 107 days were gradually reduced to 80% of their free-feeding weight. When weights were stable they were trained to run in an alley for food rewards given on every trial (continuous reinforcement, CR) or on a random 50% of trials (partial reinforcement, PR), then the running response was extinguished. A very clear and similar partial reinforcement extinction effect (PREE) was demonstrated in the previously malnourished and control rats when reward was discontinued. That is, PR groups showed greater persistence as compared with CR groups. During acquisition, however, differences in running speed were observed in the goal section between 6-25 PR and 25-25 PR groups, and between 6-25 CR and 25-25 CR groups. The latter may be due to differences between the nutritional groups in food motivation.