Retrieval-related Eye Movements Are Predictive of Memory Precision.

Eye movements are predictive of successful episodic memory encoding and retrieval, but it is unclear whether they reflect the precision of retrieved memory content. Here, we examined relationships between eye fixations, memory precision, and fMRI BOLD activity. At study, participants were presented with object images, each placed at a random location on a circle. At test, both studied and new images were presented. Participants were instructed to recall and signal the studied location of each image, guessing if necessary. They then indicated if the image had been studied. Simultaneous fMRI and eye-tracking data were acquired during the test phase. For correctly recognized images, trial-wise angular distances between the studied and reported locations were fitted to a two-component mixture model. On the basis of model-derived parameters, correctly recognized images were categorized as those associated with successful location retrieval (location hits) or guesses. Location hits were further divided into high- and low-precision trials. At retrieval, fixation location predicted both successful retrieval and the precision of the retrieved location memory. In addition, across-trial fixation patterns were more similar for location hits than for guesses and for high- than for low-precision trials. The association between retrieval success and fixation precision was evident across almost the entire recall phase, whereas memory precision effects emerged around 1-1.5 sec after image onset. Fixation precision and pattern similarity each predicted trial-wise memory precision independently of hippocampal BOLD activity, which also predicted memory precision. Taken together, the findings indicate that eye movements during retrieval track the fidelity of retrieved mnemonic content.