When encoding yields remembering: insights from event-related neuroimaging

To understand human memory, it is important to determine why some experienc es are remembered whereas others are forgotten. Until recently insights int o the neural bases of human memory encoding, the processes by which informa tion is transformed into an enduring memory trace, have primarily been deri ved from neuropsychological studies of humans with select brain lesions. Th e advent of functional neuroimaging methods, such as positron emission tomo graphy (PET) and functional magnetic resonance imaging (fMRI), has provided a new opportunity to gain additional understanding of how the brain suppor ts memory formation. Importantly, the recent development of event-related f MRI methods now allows for examination of trial-by-trial differences in neu ral activity during encoding and of the consequences of these differences f or later remembering. In this review, we consider the contributions of PET and fMRI studies to the understanding of memory encoding, placing a particu lar emphasis on recent event-related fMRI studies of the Dm effect: that is , differences in neural activity during encoding that are related to differ ences in subsequent memory We then turn our attention to the rich literatur e on the Dm effect that has emerged from studies using event-related potent ials (ERPs). It is hoped that the integration of findings from ERP studies, which offer higher temporal resolution, with those from event-related fMRI studies, which offer higher spatial resolution, will shed new light on whe n and why encoding yields subsequent remembering.