Disruption of central-place foraging in the rat following lesions of the dorsomedial thalamic nucleus

The neural basis of central-place foraging was investigated in the laboratory rat, using a six-arm radial maze. Pieces of cheddar cheese of different sizes were placed on the ends of the maze arms, and preoperative central-place foraging behavior was monitored. Then bilateral electrolytic lesions were made in the fimbria fornix (FF), amygdala (AMY), medial frontal cortex (MFC), dorsomedial thalamic nucleus (MD), and combined MFC-MD, and a comparison was made with control animals on the tendency to carry pieces of cheese to the center of the radial-arm maze. Rats with more than 77% destruction of the MD exhibited a reduction in food-carrying behavior and a concomitant increase in eating food items at the ends of arms, in comparison with control animals. Rats with less than 77% destruction of the MD exhibited some reduction in food-carrying behavior, but they did not differ significantly from controls. Rats with lesions of the FF, AMY, and MFC did not exhibit any reduction in food-carrying behavior. These findings suggest that the MD plays a role in adaptive food-carrying behaviors that are involved in central-place foraging.