FIG. 1 Histogram distribution of individual animals as a function of defensive boxing in the shock box. Defensive boxing performance measured as the percentage' of total shocks to which animals responded with boxing. A. Performance on first test for all animals: preoperative test for experimental animals and first of two tests for normal controls. B. Second test for normal controls. C. One week postoperative test for experimental animals (lesioned). Animals with greater than 50% damage to the midbrain central gray are cross-hatched.