Visual Cortex Responds to Invisible Objects

When one object passes in front of another we know that the occluded object has not vanished, and yet representations in our visual cortex have been assumed not to reflect this information. Instead, such "object permanence" information has been thought to require active maintenance, perhaps with help from prefrontal regions, thus explaining why young children (with underdeveloped prefrontal cortices) often fail to show behavior that is consistent with knowledge of object permanence.

A recent study by Hulme & Zeki elaborates this view by presenting 13 subjects in an fMRI scanner with faces or houses which were either directly visible or occluded by another object.

The results showed that the fusiform gyrus was activated across both occluded and visible events for faces, and analogous results in the lateral occipital cortex for houses. That is, these regions which have been thought to respond to visually-present objects also showed similar responses for objects which were not visible!

In addition, for both types of stimuli, left ventral premotor cortex was more active for occluded than visible stimuli. This result suggests that premotor regions may somehow be involved in maintaining visual representations even in the absence of direct visual perception.

This claim is consistent with previous work, cited by the authors, showing that premotor cortex may support object permanence in infancy. Other researchers have since cited this work as indicating a potential role for "motoric simulation" in the development of basic cognitive skills.