Object ensemble processing in human anterior-medial ventral visual cortex.

Our visual system can extract summary statistics from large collections of similar objects without forming detailed representations of the individual objects in the ensemble. Such object ensemble representation is adaptive and allows us to overcome the capacity limitation associated with representing specific objects. Surprisingly, little is known about the neural mechanisms supporting such object ensemble representation. Here we showed human observers identical photographs of the same object ensemble, different photographs depicting the same ensemble, or different photographs depicting different ensembles. We observed fMRI adaptation in anterior-medial ventral visual cortex whenever object ensemble statistics repeated, even when local image features differed across photographs. Interestingly, such object ensemble processing is closely related to texture and scene processing in the brain. In contrast, the lateral occipital area, a region involved in object-shape processing, showed adaptation only when identical photographs were repeated. These results provide the first step toward understanding the neural underpinnings of real-world object ensemble representation.