AbstractAfter both unilateral and bilateral lesions in globus pallidus conditioned avoidance responses were extinguished more rapidly than in normal and control operated cats. This was observed at a time when retention had returned to normal. Animals with bilateral lesions in globus pallidus tested 30 days after the operation learned the avoidance response slower than normal and control operated cats. Retention tested 30 days after bilateral lesions in globus pallidus was impaired as compared with normal and control operated cats. Sixty days postoperatively retention was normal. Therefore a memory defect cannot account for the rapid extinction observed more than 60 days postoperatively; it may be explained by diminished fear.