Comparative cognition, hippocampal function, and recollection

Aristotle (350BC) contended that “...other animals (as well as man) have memory, but, of all that we are acquainted with, none, we venture to say, except man, shares in the faculty of recollection.” Here Aristotle distinguishes “memory,” as an elementary matching of current sensations to impressions from prior experience, from the capacity for reminiscence, as the ability to mentally reconstruct past experiences. Jumping to current times, Tulving (1983, 2002) characterized animals as having the capacity for acquiring semantic knowledge, but claimed that episodic recollection “... has evolved only once, and in only one species, although other species would benefit from it as much as do humans.” Neither Aristotle nor Tulving employed experimental evidence in support of their claims, but several other contemporary researchers have, with indecisive results, such that there is currently no consensus on whether animals have the capacity for recollection (reviewed in Clayton, Bussey, & Dickinson, 2003; Clayton, Bussey, Emery, & Dickinson, 2003; Hampson & Schwartz, 2004; see also Roberts, 2005). This literature will not be critiqued again here. Instead, I will What is conscious recollection? Is it special to humans or do animals have this capacity as well? What brain circuitry supports the kinds of information processing that constitute recollection? This review will outline recent evidence from studies on rodents, monkeys and humans bearing on these questions. This review focuses on a comparative approach that identified features of recollection that can be studied across species, explores these elements of recollection in animals, and examines in animals the role of the medial temporal areas that are critically involved in conscious recollection in humans. Substantial evidence indicates that animals exhibit all the fundamental features of recollection, that these abilities depend on the hippocampus in animals as well as humans, and that neuronal representations in the hippocampus reflect information processing fundamental to the features of recollection. In addition, the functional circuitry of the hippocampal system is largely conserved across species, and its organization suggests information processing mechanisms that support the features of recollection are common across species.