Distinct visuo-motor brain dynamics for real-world objects versus planar images.

Ultimately, we aim to generalize and translate scientific knowledge to the real world, yet current understanding of human visual perception is based predominantly on studies of two-dimensional (2-D) images. Recent cognitive-behavioral evidence shows that real objects are processed differently to images, although the neural processes that underlie these differences are unknown. Because real objects (unlike images) afford actions, they may trigger stronger or more prolonged activation in neural populations for visuo-motor action planning. Here, we recorded electroencephalography (EEG) when human observers viewed real-world three-dimensional (3-D) objects or closely matched 2-D images of the same items. Although responses to real objects and images were similar overall, there were critical differences. Compared to images, viewing real objects triggered stronger and more sustained event-related desynchronization (ERD) in the μ frequency band (8-13 Hz) - a neural signature of automatic motor preparation. Event-related potentials (ERPs) revealed a transient, early occipital negativity for real objects (versus images), likely reflecting 3-D stereoscopic differences, and a late sustained parietal amplitude modulation consistent with an 'old-new' memory advantage for real objects over images. Together, these findings demonstrate that real-world objects trigger stronger and more sustained action-related brain responses than images do. The results highlight important similarities and differences between brain responses to images and richer, more ecologically relevant, real-world objects.