Brief encounters with real objects modulate medial parietal but not occipitotemporal cortex

Abstract

Humans are skilled at recognizing everyday objects from pictures, even if we have never encountered the depicted object in real life. But if we have encountered an object, how does that real-world experience affect the representation of its photographic image in the human brain? We developed a paradigm that involved brief real-world manual exploration of everyday objects prior to the measurement of brain activity with fMRI while viewing pictures of those objects. We found that while object-responsive regions in lateral occipital and ventral temporal cortex were visually driven and contained highly invariant representations of specific objects, those representations were not modulated by this brief real-world exploration. However, there was an effect of visual experience in object-responsive regions in the form of repetition suppression of the BOLD response over repeated presentations of the object images. Real-world experience with an object did, however, produce foci of increased activation in medial parietal and posterior cingulate cortex, regions that have previously been associated with the encoding and retrieval of remembered items in explicit memory paradigms. Our discovery that these regions are engaged during spontaneous recognition of real-world objects from their 2D image demonstrates that modulation of activity in medial regions by familiarity is neither stimulus nor task-specific. Overall, our results support separable coding in the human brain of the visual appearance of an object from the associations gained via real-world experience. The richness of object representations beyond their photographic image has important implications for understanding object recognition in both the human brain and in computational models.