Alteration in escape responding in the cat. A lesion and degeneration and comparison following stimulation studies

15 cats were trained to cross a hurdle in a shuttle box when stimulated through a single bipolar electrode chronically implanted in the subthalamic, mesencephalic and most rostral pontine tegmentum. A lesion was then made through one or both electrode poles. Upon recovery, three patterns of response emerged: (1) crossing with higher threshold or longer latencies; (2) no crossing, or (3) no change in crossing. The response pattern correlated with the anatomic findings. The nine animals that crossed before but not after the lesion, showed either lesions or heavy axonal and terminal degeneration in the H2 field.