Unattended working memory items are coded by persistent activity in human medial temporal lobe neurons

The role of persistent neural activity in working memory storage is well documented, particularly in tasks where memorized items are of equal importance. However, the encoding mechanism for unattended items, often considered as 'activity silent', remains poorly understood. Here we recorded the activity of image-selective neurons in the medial temporal lobe while subjects (n = 12) shifted attention between concurrently stored memory items. Our results demonstrate that both attended and unattended memory items are encoded through persistent activity. Additionally, we observed a dynamic transformation in the neuronal subspace following cue presentation, reflecting a shift in how information was maintained. While information about the unattended item was decodable at the single-trial level from preselected image-selective cells, it was not decodable from the entire population of medial temporal lobe cells. These findings support models of persistent activity and challenge the notion that unattended items are stored via 'activity-silent' mechanisms.