A finite set of content-free pointers in visual working memory: magnetoencephalography (MEG) evidence

Human visual working memory (VWM) is known to be capacity-limited, but the nature of this limit continues to be debated. Recent work has proposed that VWM is supported by a finite (~3) set of content-free pointers, acting as stand-ins for individual objects and binding features together. According to this proposal, the pointers do not represent features within themselves, but rather bind features represented elsewhere together. The current study set out to test if neural hallmarks resembling these content-free pointers can be observed with magnetoencephalography (MEG). Based on two VWM delay-match-to-sample experiments (N = 20 each) examining memory for simple and complex objects, we report a sustained response in MEG over right posterior cortex whose magnitude tracks the core hypothesized properties of this content-free pointer system: load-dependent, capacity-limited, and content-free. These results provide novel evidence for a finite set of content-free pointers underlying VWM.