Impaired gustatory neophobia following traumatic brain injury in rats

To investigate the function of the amygdala following traumatic brain injury (TBI), rats were tested on a gustatory neophobia task that is sensitive to amygdala and hippocampal damage. Rats were either injured at a moderate level of fluid percussion injury (2.1 atm) or surgically prepared but not injured (sham-injury). Seven days after injury (n = 8) or sham injury (n = 9), rats were habituated to the testing chamber without food items present for 30 min. All rats were then food deprived. Twenty-four hours later, rats were placed in the testing chamber for 30 min and allowed to eat freely from four dishes of different foods: rat chow, raisins, potatoes, and cookies. Results showed that injured and sham-injured rats did not differ in their ability to find hidden food, suggesting that TBI does not produce an enduring impairment of olfaction. There was also no difference in the total amount of food eaten between injured and sham groups (p > 0.05). The percentage of each type of food consumed did differ between the two groups with sham controls consuming more familiar food (rat chow) compared to the unfamiliar foods (p < 0.01). The injured animals distributed their eating evenly among the four foods with no particular preference for any one food (p < 0.05). This pattern of eating behavior in injured animals is similar to animals that have lesions to both the hippocampus and amygdala (Sutherland and McDonald, 1990). Therefore, the results of this experiment suggest that, in addition to the hippocampus, the amygdala may also contribute to the behavioral changes observed following TBI.