Attentional selection for short-term memory: gaze-direction at encoding predicts retrieval activity in posterior parietal cortex

Remembering of complex visual stimuli demands a tight interplay between memory functions and attentional selection. Here, we examined this interplay during free-viewing of complex and dynamic visual scenes (8 videos, approx. 5 min each). We used patterns of fixation to index attentional selection for encoding in short-term memory, and exploited these to predict brain activity during retrieval. Each video was characterized by 8 different actors/actresses who entered twice into the scene, at unpredictable times: the first appearance corresponded to the memory “encoding” phase, while the second presentation represented the memory “retrieval” phase. We monitored gaze-direction and used the tendency of the subjects to look towards each actor during the encoding phase as an index of attentional selection. Accordingly, we categorised each actors as: “high probability of selection/encoding”, when subjects fixated the actor more during the first than the second presentation; versus “low probability of selection/encoding”, when subjects fixated the actor more during the second than the first presentation. The fMRI analyses considered the brain activity during retrieval, as a function of fixation probability at encoding. This revealed activation in the posterior parietal cortex (SPG), plus occipital visual areas (FFA). We conclude that eye-movements during encoding can predict retrieval-related activation.