Noam Khayat¹ (), Shaul Hochstein¹; ¹Hebrew University of Jerualem, ²ELSC Edmond & Lily Safra Center for Brain Sciences, ³Life Sciences Inst

Ensemble perception refers to the visual system's ability to extract summary statistical information from groups of similar objects, commonly assessed through the efficiency of perceptual averaging. While this phenomenon has been extensively studied and characterized behaviorally, its underlying neural mechanisms remain largely unexplored. Using functional magnetic resonance imaging (fMRI) and Multi-Voxel Pattern Analysis (MVPA), we investigated how the neural representation of ensemble averaging—specifically for line orientations—can be decoded across cortical regions. Our experimental paradigm was designed to identify regions that encode explicit ensemble average information, with participants instructed to actively perceive and passively report the average orientation in a subsequent two-alternative forced choice (2-AFC) task. While some studies have suggested that the Parahippocampal Place Area (PPA) may specialize in ensemble perception and others have proposed that the neural representation of ensemble percepts is formed by pooling signals across multiple levels of the visual processing stream, our findings reveal that the Lateral Occipital Complex (LOC) also encodes ensemble average information, as evidenced by significantly above-chance classification accuracies. This result is novel and surprising, as the LOC is traditionally associated with object recognition and perception, independent of low-level visual features. We demonstrate that, beyond its well-established role in recognizing individual objects, the LOC also processes information of groups of objects perceived as unified wholes.

Acknowledgements: Israel Science Foundation (ISF)