Revisiting the maturation of medial temporal lobe memory functions in primates.

In a review of the literature on the development of the medial temporal lobe region in humans, monkeys, and rodents, Bachevalier and Beauregard indicated that in primates, memory functions subserved by this neural system emerge early in life and increment gradually with further postnatal maturation. Furthermore, they stated that the late-developing memory functions of normal neonates was more likely owing to the slow maturation of the association areas of the cortex than to the slow maturation of the hippocampal formation. This conclusion was based on the limited knowledge concerning the development of hippocampal-dependent memory functions and the maturational events in the medial temporal lobe of monkeys. Over the last decade, however, more information has accumulated about the structural, functional, and behavioral changes occurring throughout ontogeny in monkeys that suggest a refinement of this view. Whereas there is still much to be discovered, we thought it timely to put into perspective the latest findings in hope of shedding light on memory development in general, and particularly, on the role of medial temporal lobe structures in infant and adult memory. [Note: Hippocampal formation refers to the hippocampus proper (Ammon’s fields), dentate gyrus, and subicular complex. Hippocampal region refers to the hippocampal formation and the adjacent entorhinal, perirhinal, and parahippocampal cortex.]