The circuit for visual object memory in the monkey was found earlier to depend on interaction between the cortical visual system and the limbic system, comprising the medial temporal lobe, medial diencephlon, and ventromedial frontal (VMF) region. We have now found that this form of visual memory, which includes object recognition and object-reward recall, depends particularly on the orbitofrontal as compared to the anterior cingulate component of the VMF region. This finding, together with recent evidence that the rhinal cortex is the critical medial temporal area for object memory (see LN-02736), indicates that the essential limbic circuit for this form of memory is comprised mainly of the rhinal cortex, orbitofrontal cortex, and the magnocellular division of the thalamic medial dorsal nucleus. Although rhinal lesions nearly preclude monkeys from recognizing objects presented a minute or two earlier, they do not prevent very short-term memory; indeed, memory of a new object for five seconds or less is essentially normal after rhinal lesions. This residual ability can be demonstrated by training monkeys with rhinal lesions to perform delayed nonmatching-to-sample (DNMS) with trial-unique stimuli and short intratrial delays. Under these conditions the lesioned monkeys appear to learn DNMS not as a cognitive principle based on recognition memory but as a behavioral rule based on habit formation. This type of rule learning in the absence of the rhinal cortex depends on interaction between the cortical visual system and the frontal lobe, the ability being abolished when ventral frontal lesions (including inferior frontal and orbitofrontal cortex) are superimposed on rhinal lesions. A simpler type of habit formation, namely, concurrent visual discrimination learning with 24-hour intertrial intervals, depends instead on interaction between the cortical visual system and its neostriatal targets in the ventrocaudal putamen and tail of caudate nucleus; our new evidence indicates that impairment in this form of learning is directly proportional to the extent of damage to these structures.