Supramodal and cross-modal representations of working memory in higher-order cortex.

Working memory is essential for guiding our behaviors in daily life, where sensory information continuously flows from the external environment. While numerous studies have shown the involvement of sensory areas in maintaining working memory in a feature-specific manner, the challenge of utilizing retained sensory representations without interference from incoming stimuli of the same feature remains unresolved. To overcome this, essential information needs to be maintained dually in a form distinct from sensory representations. Here, using working memory tasks to retain braille patterns presented tactually or visually during fMRI scanning, we discovered two distinct forms of high-level working memory representations in the parietal and prefrontal cortex, together with modality-dependent sensory representations. First, we found supramodal representations in the superior parietal cortex that encoded braille identity in a consistent form, regardless of the involved sensory modality. Second, we observed that the prefrontal cortex and inferior parietal cortex specifically encoded cross-modal representations, which emerged during tasks requiring the association of information across sensory modalities, indicating a different high-level representation for integrating a broad range of sensory information. These findings suggest a framework for working memory maintenance that incorporates two distinct types of high-level representations-supramodal and cross-modal-operating alongside sensory representations.