EEG signals represent updated memory representations in working memory

Visual short-term memory (VSTM) creates continuity of representations over time. Working memory, in addition, gives us access to these representations to manipulate or update them. Visual representations stored in VSTM have been successfully reconstructed from measurements of neural activity. However, it is unclear whether the updated state of a remembered item is reflected in these neural representations. To ask this question, we measured alpha-band oscillations (8-12Hz), associated with visual attention, and sustained EEG potentials (<6Hz), associated with visual short-term memory maintenance, while participants remembered and updated a sinusoid gabor in visual short-term memory. In the task, participants were asked to mentally rotate a grating based on a color cue that indicated whether participants should rotate the remembered item 1) clockwise, 2) counter-clockwise, or 3) not at all. We found that reconstructions from sustained EEG (< 6 Hz) reflected updated representations with higher fidelity while alpha-band frequency (8-12Hz) computed broad scope of reconstructions including initial sensory representations. These results suggest that neural signal carries not only the sensory information but also manipulated mnemonic representations.