Human posterior parietal cortex maintains color, shape and motion in visual short-term memory

We used functional magnetic resonance imaging (fMRI) to investigate the neural substrate of visual short-term memory for objects defined by features processed in the dorsal and the ventral visual streams. Here we adopted the conventional delayed recognition task, whereas in addition to the more commonly used visual features of color and shape, motion direction was applied to define an item. Our behavioral results indicated that the capacity limit of visual short-term memory of motion direction was approximately two, which was significantly lower than those of color and shape, about three or four. We also found that storage capacity was significantly reduced when subjects were required to retain all three features superimposed in space. Meanwhile, fMRI results revealed that activity in the posterior part of the superior parietal lobe was memory–load dependent for all three features indicating that it collects and stores visual information from both the two visual processing streams, whereas the anterior part was load dependent only for motion.