Transformed Visual Working Memory Representations in Human Occipitotemporal and Posterior Parietal Cortices

Recent fMRI studies reported transformed representations between perception and visual working memory (VWM) in the human early visual cortex (EVC). This is inconsistent with the still widely cited original proposal of the sensory account of VWM, which argues for a shared perception-VWM representation based on successful cross-decoding of the two representations. Although cross-decoding was usually lower than within-VWM decoding and consistent with transformed VWM representations, this has been attributed to experimental differences between perceptual and VWM tasks: once they are equated, the same representation is expected to exist in both. Including human participants of both sexes, this study compared target and distractor representations during the same VWM delay period for the same objects, thereby equating experimental differences. Even with strong VWM representations present throughout the occipitotemporal cortex (OTC, including EVC) and posterior parietal cortex (PPC), fMRI cross-decoding revealed significant representational differences between distractors (perception) and targets (VWM) in both regions. Similar differences existed between target encoding (perception) and delay (VWM), being greater in OTC than PPC, indicating more invariant target representations in PPC than OTC. As only part of the sensory input is usually task-relevant, sustaining sensory input in VWM without selection/refinement/consolidation is both taxing and unnecessary. Transformed representations, mediated by task goals and associative areas coding task-relevant information (e.g., PPC), can easily account for these and other recent findings. A task-driven transformed account of VWM thus better captures the nature of VWM representation in the human brain (including EVC) than the sensory representations originally proposed by the sensory account of VWM.