Parietal Cortex and Object Permanence

Parietal cortex is critical for the maintenance of object information over delays. This is true both in tests of working memory (e.g., 1, 2 and 3) as well as simple visual manipulations involving the occlusion of visible objects.

A great example is this study by Olson et al., who demonstrated that neurons in human intraparietal sulcus (IPS) and middle temporal (MT) cortex increased their activity in response to objects which disappeared due to occlusion (i.e., they were hidden behind another object) relative to those which simply disappeared without an occluder. This was particularly robust in the case of IPS, and was observed even in the context of a task in which no responses were required - indicating the IPS result did not merely reflect motoric preparation or response-related intentions.

This has been replicated in subsequent work, with the important caveat that other regions are also more active during occlusion than other visual events (including frontal cortex, which is more traditionally associated with object permanence).

Other work also finds parietal activity in object permanence paradigms among adult humans (here, although it was superior parietal lobe and precuneus, and not the IPS, and it's reported only in the supplementary information, since parietal was for some reason not an a priori ROI).

One working hypothesis is that the parietal cortex is responsible for maintenance in working memory tasks because that function - active maintenance of object information in pursuit of goals - relies on the same neural regions subserving the maintenance demands imposed by a much older problem (developmentally and evolutionarily): processing visually occluded objects.