The role of the superior intraparietal sulcus in supporting visual short-term memory for multifeature objects

Everyday objects can vary in a number of feature dimensions, such as color and shape. To identify and recognize a particular object, often times we need to encode and store multiple features of an object simultaneously. Previous studies have highlighted the role of the superior intraparietal sulcus (IPS) in storing single object features in visual short-term memory (VSTM), such as color, orientation, shape outline, and shape topology. The role of this brain area in storing multiple features of an object together in VSTM, however, remains mostly unknown. In this study, using an event-related functional magnetic resonance imaging design and an independent region-of-interest-based approach, how an object's color and shape may be retained together in the superior IPS during VSTM was investigated. Results from four experiments indicate that the superior IPS holds neither integrated whole objects nor the total number of objects (both whole and partial) stored in VSTM. Rather, it represents the total amount of feature information retained in VSTM. The ability to accumulate information acquired from different visual feature dimensions suggests that the superior IPS may be a flexible information storage device, consistent with the involvement of the parietal cortex in a variety of other cognitive tasks. These results also bring new understanding to the object benefit reported in behavioral VSTM studies and provide new insights into solving the binding problem in the brain.