| Scope and method of study. This study focused on the issues of developmental differences in long-term recognition memory between 3- and 5-month-old infants and the modification of an event-related potential (ERP) paradigm to test the behaviorally-established phenomena of reactivation. Participants in the study were 48 3-month-old infants from the Stillwater, Oklahoma area. Infants received 100 tones then 50 random presentations of the same tone (familiar) and a novel tone 24-hours later. This data was used to determine developmental differences in long-term recognition memory. To test for reactivation, the infants returned three weeks later and given 100 familiar tones, 10 familiar tones, 10 novel tones, or no tones, followed 24-hours later with presentation of 50 familiar and 50 novel tones. Five different ERP measures, average peak amplitude, average peak latency single-trial amplitude, amplitude variability, and latency variability, were used as dependent measures. A priori t-tests, modified to maintain acceptable familywise error rates, were used to test established hypotheses. Post hoc analyses of variance were run to establish addition trends.;Findings and conclusions. The three-month-old infants, when familiarized with a stimulus and tested 24-hours later showed an increase in ERP amplitude at the P2 peak for both the familiar and novel stimulus indicating the experience with one tone frequency generalizes to similar tone frequencies. This contradicts with previous findings with 5-month-olds which had a increase in amplitude only to the familiar stimulus on the second day. Findings for the N2 peak were the same for both age groups possibly indicating two different processing functions are attributing to the ERP wave form. The results for forgetting, necessary for the indication of reactivation, were mixed making it unclear if forgetting had occurred. Varying results across the three of the dependent measures indicated that the experience on the third day resulted in differences that were group dependent for the ERP amplitude of the fourth day stimuli. |
