Abstract
Introduction: There are two long-standing debates regarding the nature of visual short-term memory (VSTM) representations and their neural underpinnings. One question is whether VSTM depends on the same neural circuitry as vision or whether it functions separately. The second question is whether VSTM and attention use overlapping mechanisms. Methods: To evaluate these questions, two experiments evaluated retinotopic activation during attention and VSTM maintenance. Participants attended to and remembered the contents of two (out of four) visually presented sectors. After this they were tested for change detection on the sectors: in the first experiment change detection was performed in the same location (prospective attention encouraged), while in the second the change detection was performed centrally regardless of the sectors' location (prospective attention discouraged). Results: During the VSTM maintenance period, both univariate methods and Multi-Voxel Pattern Analysis showed evidence of spatial encoding in visual cortex only where prospective attention to the sector locations was encouraged, but no evidence when it was not required. However, spatial encoding was evident during attention in both experiments, ruling out an explanation based on power. This spatial selectivity was equivalent to that obtained from purely sensory stimulation. Conclusion: We conclude that VSTM does not use the same low-level visual circuitry as typical visual processing or attention, suggesting it is underpinned by different mechanisms than either of these. Visual processing and attention, on the other hand, appear to have similar neural correlates. We suggest that previous findings of VSTM activating visual cortex are due to residual attentional activation.
Medical Research Council.