Role of freezing and fear in avoidance decrements following mammillothalamic tractotomy in cat: II. Appetitively motivated behavior

Abstract

Although previous work (Krieckhaus, 1964a; Krieckhaus & Chi, 1966) suggests that it is unlikely that the avoidance decrements following lesions of the mammillothalamic tract (MTT) are attributable to increased freezing behavior, in each case evaluation of freezing was confounded with concomitant changes in avoidance behavior. In the present experiment, freezing following MTT lesions was evaluated independently of avoidance behavior by using either the conditioned emotional response (CER) or an appetitively motivated visual discrimination in which the incorrect response was punished. In neither case was there any indication of increases in freezing or other signs of fear following lesions of the MTT. We thus conclude that the reported increases in freezing behavior following MTT lesions are a result of rather than a cause of a primary decrement in avoidance behavior.