Response profiles to uni- and bilateral stimulation in higher-order visual cortex

We used functional Magnetic Resonance Imaging (fMRI) at 7T, complemented with additional 3T data. Six healthy participants, with normal or corrected to normal vision, saw stimuli of two different object classes (presented in blocks) while performing a visual detection task. Whereas fixation was kept at the middle of the screen, stimuli were presented at peripheral locations (at 6° eccentricity in the lower visual quadrant). Crucially, a stimulus could either be presented in isolation in one hemifield (unilateral stimulation), or could be combined with a simultaneously presented stimulus in the opposite hemifield (bilateral stimulation). Focusing on the entire ensemble of visually responsive voxels in occipitotemporal cortex, we assessed to what extent object category decoding was possible based on distributed voxel activation patterns in either hemisphere both within and across hemifields, as previously shown for category-selective regions at 3T (e.g., Cichy et al., 2011, Cichy et al., 2013). Furthermore, we examined how object position and identity preferences are reflected in (rank ordered) voxel-wise response amplitudes. In addition, we quantified the consistency of the overlap in activations to uni- and bilateral stimulus configurations across subjects. Finally we explored how to optimally predict the response to bilateral stimulus configurations based on the responses to their constituent elements shown in isolation.