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 s ensitive to amygdala and hippocampaI 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 depriv ed. Twenty-four hours later, rats were placed in the testing chamber f or 30 min and allowed to eat freely from four dishes of different food s: rat chow, raisins, potatoes, and cookies. Results showed that injur ed and sham-injured rats did not differ in their ability to find hidde n food, suggesting that TBI does not produce an enduring impairment of olfaction. There was also no difference in the total amount of food e aten between injured and sham groups (p > 0.05). The percentage of eac h type of food consumed did differ between the two groups with sham co ntrols consuming more familiar food (rat chow) compared to the unfamil iar foods (p < 0.01). The injured animals distributed their eating eve nly among the four foods with no particular preference for any one foo d (p > 0.05). This pattern of eating behavior in injured animals is si milar to animals that have lesions to both the hippocampus and amygdal a (Sutherland and McDonald, 1990). Therefore, the results of this expe riment suggest that, in addition to the hippocampus, the amygdala may also contribute to the behavioral changes observed following TBI.