Our next analysis turned to the question of how hippocampal output

might EPZ 6438 influence scene perception. Previous work has described a network of occipitotemporal areas that contribute to scene perception, including the lingual gyri (Aguirre et al., 1998 and Menon et al., 2000) and the lateral occipital complex (LOC; Malach et al., 1995 and Park et al., 2011). We therefore conducted a psychophysiological interaction (PPI) analysis in order to determine whether the hippocampus contributes to detection of scene changes through functional interactions with occipitotemporal visual areas. The seed region for the PPI analysis was the left posterior hippocampus ROI from the preceding analyses, Rucaparib and ROIs for the left and right lingual gyrus and the left and right LOC were selected by identifying voxels in these regions that showed greater activation for scenes than for faces. For both the left and right lingual gyrus and LOC, functional connectivity with the posterior hippocampus increased with increasing perceptual decision confidence (left lingual gyrus, t(17) = 1.60, p = 0.06; right lingual gyrus, t(17) = 2.05, p = 0.03; left LOC, t(17) = 1.74, p = 0.05; right LOC, t(17) = 1.89, p = 0.04). These results are similar to findings that the posterior hippocampus exerts top-down modulation of visual cortical areas in a task that involves constructing and maintaining scene representations over a brief amount of time

( Chadwick et al., 2012). The current findings suggest that the hippocampus forms Ketanserin a network with visual scene processing regions in the service of assessing the strength

of perceptual match/mismatch. The current study yielded converging patient and neuroimaging evidence in support of a role for the hippocampus in visual scene perception (Lee et al., 2012). Furthermore, the results implicate the hippocampus specifically in strength-based perceptual discriminations, but not in state-based perception. Patients with hippocampal damage, including those with focal hippocampal lesions, were selectively impaired at making perceptual judgments based on continuously graded strength information, and hippocampal activity varied in a graded manner with perceptual decision confidence. Our findings potentially reconcile the controversy about MTL involvement in perception by suggesting that the hippocampus may be specifically necessary for one kind of perceptual judgment—perception based on the strength of relational match. Indeed, our data demonstrate that if only binary same/different judgments were collected, the presence or absence of a deficit in patients would depend on the response criteria used by participants. According to some theories, the hippocampus is necessary for complex spatial perceptual decisions in which conjunctions of features, rather than individual features, are diagnostic for task performance (Lee et al.