Parietal and early visual cortices encode working memory content across mental transformations

- A mental rotation task is used to investigate mental representations after transformations.
- Transformed visual working memory content is encoded in visual and parietal cortices.
- Representations are based on a common neural code before and after mental rotation.
- The results represent evidence for a generalized visual workspace in posterior brain regions.

Active and flexible manipulations of memory contents “in the mind's eye” are believed to occur in a dedicated neural workspace, frequently referred to as visual working memory. Such a neural workspace should have two important properties: The ability to store sensory information across delay periods and the ability to flexibly transform sensory information. Here we used a combination of functional MRI and multivariate decoding to indentify such neural representations. Subjects were required to memorize a complex artificial pattern for an extended delay, then rotate the mental image as instructed by a cue and memorize this transformed pattern. We found that patterns of brain activity already in early visual areas and posterior parietal cortex encode not only the initially remembered image, but also the transformed contents after mental rotation. Our results thus suggest that the flexible and general neural workspace supporting visual working memory can be realized within posterior brain regions.