Interactive shape and color representation in visual working memory for colored objects in the human occipitotemporal cortex.

Two defining visual features of a real-world object are its shape and color. While previous fMRI pattern decoding studies showed that these features are represented in a largely orthogonal and independent manner in the human occipitotemporal cortex (OTC) during visual perception, how they are coded together in visual working memory (VWM) remains unknown. Here, we asked human participants to retain a real-world object's shape and color together in VWM. Using fMRI pattern decoding, we trained a linear classifier to decode two object shapes in one color to then decode the same two object shapes either in the same color (within-decoding) or in a different color (cross-decoding). During VWM encoding, replicating prior findings, we found significant cross-decoding and no drop in cross-decoding compared to within-decoding across OTC, indicating orthogonal and independent shape and color coding. During VWM delay, we again found significant cross-decoding, but more critically, a significant cross-decoding drop in OTC shape-selective areas and ventral color areas, indicating interactive shape and color coding in these areas in VWM. To our knowledge, this is the first time that interactive shape and color representations are reported in VWM in the human brain using fMRI pattern decoding. Sensory representations of an object's shape and color are thus transformed during VWM delay, likely tracking the demand of VWM to enable more efficient information storage.