Perception of Impossible Scenes Reveals Differential Hippocampal and Parahippocampal Place Area Contributions to Spatial Coherency.

Surprisingly little is known about how the brain combines spatial elements to form a coherent percept. Regions that may underlie this process include the hippocampus (HC) and parahippocampal place area (PPA), regions central to spatial perception but whose role in spatial coherency has not been explored. Participants were scanned with functional MRI while they judged whether Escher-like scenes were possible or impossible. Univariate analyses revealed differential HC and PPA involvement, with greater HC activity during spatial incoherency detection and more PPA activity during spatial coherency detection. Recognition and eye-tracking data ruled out long- or short-term memory confounds. Multivariate statistics demonstrated spatial coherency-dependent functional connectivity for the HC, but not PPA, with greater HC connectivity to various brain regions including lateral occipital complex during spatial incoherency detection. We suggest the PPA is preferentially involved during the perception of spatially coherent scenes, whereas the HC binds distinct features to create coherent representations.