The overall goal of the proposed research is to investigate the relative contributions of familiarity and recollection to the development of visual recognition memory in infants as assessed by the visual-paired comparison (VPC). Despite the extent to which the VPC has been used to study memory in infants, a key distinction has been overlooked in interpreting results of this research: that between conscious recollection and assessments of familiarity. Recollection involves the retrieval of qualitative information about the context in which an item was previously encountered, and is thought to depend critically on the hippocampus. Familiarity, on the other hand, involves the assessment of global similarities between study and test items that appears to be mediated by perirhinal cortex and high-level visual association areas. The extent to which recollection and familiarity contribute to visual recognition memory in infants is a key focus of the present research, and is critical to our understanding of both memory development and brain development in infants. The hypotheses being tested are that (a) familiarity contributes to infant visual recognition memory earlier in development than recollection, and (b) recollection does not emerge until sometime during the second year of life. To test these hypotheses, we will examine the effects of manipulations known to dissociate recollection and familiarity in adults on infants'performance in the VPC.
The specific aims of this application are to: (1) Examine the contribution of recollection to infant visual recognition memory. Separate groups of 9-, 12-, 18-, and 24-month-old infants will be tested in two versions of the VPC: one in which the orientation of the familiar object stays the same from familiarization to test (same- orientation condition), and another in which a mirror-inversion of the familiar object is presented at test (mirror-reflection condition). If recollection contributes to infants'performance in the VPC, then study-test changes in reflection should disrupt infants'recognition memory in the VPC. (2) Examine the contribution of familiarity to infant visual recognition memory. Separate groups of 9-, 12-, 18-, and 24-month-old infants will be tested in two versions of the VPC: one in which each test trial is preceded by a masked presentation of the familiar object (same-prime condition), and another in which test trials are preceded by a masked presentation of an unfamiliar object (different-prime condition). If familiarity contributes to infants'recognition memory in the VPC, then brief pre-test presentations of the familiar object should facilitate infants'performance in the VPC. The work proposed here is the first step in a long-term plan to systematically examine the electrophysiological correlates of recollection and familiarity in infants.
The outcome of the proposed research will provide important new information about memory development in typically developing infants. This knowledge could dramatically change the way we think about infant cognition, and will ultimately help us understand how disruptions in the development of brain systems involved in learning and memory may give rise to developmental disorders.
