TO ASCERTAIN WHETHER THE ABOLISHMENT OF VISUAL DISCRIMINATION HABITS BY DAMAGE TO THE AREA OF THE RED NUCLEUS RESULTS PRIMARILY FROM A SENSORY-PERCEPTUAL LOSS OR AN INTEGRATIVE-MEMORY DEFICIT, 31 NORMAL AND MIDBRAIN DAMAGED ADULT MALE ALBINO WISTAR RATS WERE TESTED FOR RETENTION OF A PREOPERATIVELY LEARNED VISUAL SIZE DISCRIMINATION, TESTED ON SIZE DISCRIMINATION THRESHOLD, AND THEN TESTED FOR RETENTION OF A VISUAL FORM DISCRIMINATION HABIT. BILATERAL RED NUCLEUS LESIONED SS DID SIGNIFICANTLY POORER ON RETENTION TASKS THAN CONTROLS OR SS RECEIVING MORE DORSAL OR ASYMMETRICAL MIDBRAIN LESIONS. RED NUCLEUS SS PERFORMED MORE POORLY THAN CONTROLS, BUT NOT OTHER MIDBRAIN SS, ON VISUAL THRESHOLD TASKS. RESULTS WERE INTERPRETED WITHIN A CENTRENCEPHALIC VIEW OF BRAIN FUNCTIONING. (PsycINFO Database Record (c) 2006 APA, all rights reserved)