Visual recognition in monkeys: effects of separate vs. combined transection of fornix and amygdalofugal pathways.

Performance on an object recognition test was assessed in monkeys with transections of either the fornix, the amygdalofugal pathways, or both. Whereas separate transection of the two pathways produced only small and unreliable effects, their combined transection produced a severe deficit. Comparison with the results of a previous study (Mishkin 1978) indicates that combined disconnection of the amygdala and hippocampus from the diencephalon yields a memory impairment similar to that following combined damage to the two limbic structures themselves. The findings suggest that recognition memory in monkeys depends on two parallel limbo-diencephalic pathways.