The precision of retrieving temporal information : behavioral and electrophysiological studies

Abstract

The knowledge of when an event took place provides benefits to episodic memory, such as distinguishing among multiple traces and learning event sequences. As a tool for understanding memory, time is appealing given its ever-changing quality, and the ease with which it is targeted at retrieval. Whereas studies of episodic retrieval typically employ categorical measures of retrieval, characterizing a continuous feature such as time warrants measures sensitive to the precision of retrieved information. Through four experiments, we adapted a paradigm for assessing the fine-grained precision of retrieval to understand the nature of judging the time at which a memory was encoded. Subjects studied a series of pictures and were subsequently tested on when they previously studied items. Temporal judgments were less accurate with passing time, with negligible guessing. Neurally, ERP amplitudes in left parietal electrodes tracked the precision of temporal judgments, with higher ERP amplitudes associated with better precision. Additionally, frequency power in both the alpha and theta bands were associated with temporal precision. Finally, while testing spatial retrieval, a correspondence emerged between spatial and temporal precision on a trial to trial basis, but a dissociation was found in which the recency effects found in temporal judgments was not present in spatial judgments. Together, these findings elucidate the role of time and space in episodic memory retrieval.