PT  - JOURNAL ARTICLE
AU  - Daniel Kaiser
AU  - Marius V. Peelen
TI  - Transformation from independent to integrative coding of multi-object arrangements in human visual cortex
AID  - 10.1101/117432
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 117432
4099  - http://biorxiv.org/content/early/2017/03/16/117432.short
4100  - http://biorxiv.org/content/early/2017/03/16/117432.full
AB  - The human visual system has adapted to process cluttered scenes containing dozens of regularly arranged objects. The regularity among objects critically contributes to the efficiency of naturalistic vision. Recent studies investigating multiple object perception have demonstrated that visual cortex responses to multi-object displays can be accurately modeled by a linear combination of responses to individual objects, revealing independent processing of simultaneously presented objects. Here we use fMRI to show that this independence partly breaks down when objects are positioned according to frequently experienced configurations. Participants viewed pairs of objects that formed minimalistic two-object scenes (e.g., a “living room” consisting of a sofa and television) presented in their regularly experienced spatial arrangement or in an irregular arrangement (with interchanged positions). Additionally, single objects were presented centrally and in isolation. Multi-voxel activity patterns evoked by the object pairs were modeled as the average of the response patterns evoked by the two single objects forming the pair. In two experiments, this approximation in object-selective cortex (OSC) was significantly less accurate for the regularly than the irregularly positioned pairs, indicating integration of individual object representations. More detailed analysis revealed a transition from independent to integrative coding along the posterior-anterior axis of the visual cortex, with the independent component (but not the integrative component) being almost perfectly predicted by object selectivity across the visual hierarchy. These results reveal a transitional stage between individual object and multiobject coding in visual cortex, providing a possible neural correlate of efficient processing of regularly positioned objects in natural scenes.