Spatial navigation is believed to be guided in part by reference to an internal map of the environment. We used functional magnetic resonance imaging (fMRI) to test for a key aspect of a cognitive map: preservation of real-world distance relationships. University students were scanned while viewing photographs of familiar campus landmarks. fMRI response levels in the left hippocampus corresponded to real-world distances between landmarks shown on successive trials, indicating that this region considered closer landmarks to be more representationally similar and more distant landmarks to be more representationally distinct. In contrast, posterior visually responsive regions such as retrosplenial complex and the parahippocampal place area were sensitive to landmark repetition and encoded landmark identity in their multivoxel activity patterns but did not show a distance-related response. These data suggest the existence of a map-like representation in the human medial temporal lobe that encodes the coordinates of familiar locations in large-scale, real-world environments.

We used functional magnetic resonance imaging (fMRI) to demonstrate the existence of a mechanism in the human lateral occipital (LO) cortex that supports recognition of real-world visual scenes through parallel analysis of within-scene objects. Neural activity was recorded while subjects viewed four categories of scenes and eight categories of 'signature' objects strongly associated with the scenes in three experiments. Multivoxel patterns evoked by scenes in the LO cortex were well predicted by the average of the patterns elicited by their signature objects. By contrast, there was no relationship between scene and object patterns in the parahippocampal place area (PPA), even though this region responds strongly to scenes and is believed to be crucial for scene identification. By combining information about multiple objects within a scene, the LO cortex may support an object-based channel for scene recognition that complements the processing of global scene properties in the PPA.

Summary Previous work using functional magnetic resonance imaging (fMRI) has shown that the identities of isolated objects can be extracted from distributed patterns of activity in the human brain [1]. Outside the laboratory, however, objects almost never appear in isolation; thus it is important to understand how multiple simultaneously-occurring objects are encoded in the visual system. Here we use multi-voxel pattern analysis to examine this issue, specifically testing whether patterns evoked by pairs of objects in the lateral occipital complex (LOC) showed an ordered relationship to patterns evoked by their constituent objects presented alone. Subjects viewed four categories of objects, presented either alone or in different-category pairs, while performing a one-back task that required attention to each item on the screen. Applying a “searchlight” pattern classification approach [2] to identify voxels with the highest signal-to-noise ratios, we found that the responses to object pairs among these informative voxels were well-predicted by the averages of their responses to the corresponding component objects. We validated this relationship by classifying patterns evoked by object pairs based on synthetic patterns created by averaging patterns evoked by single objects. These results indicate that the representation of multiple objects in LOC is governed by response normalization mechanisms similar to those reported in the visual systems of several species, including macaques [3–6]. They also suggest a coding scheme that allows patterns of population activity to preserve information about multiple objects under conditions of distributed attention, facilitating fast object and scene recognition during natural vision.

Complex visual scenes preferentially activate several areas of the human brain, including the parahippocampal place area (PPA), the retrosplenial complex (RSC), and the transverse occipital sulcus (TOS). The sensitivity of neurons in these regions to the retinal position of stimuli is unknown, but could provide insight into their roles in scene perception and navigation. To address this issue, we used functional magnetic resonance imaging (fMRI) to measure neural responses evoked by sequences of scenes and objects confined to either the left or right visual hemifields. We also measured the level of adaptation produced when stimuli were either presented first in one hemifield and then repeated in the opposite hemifield or repeated in the same hemifield. Although overall responses in the PPA, RSC, and TOS tended to be higher for contralateral stimuli than for ipsilateral stimuli, all three regions exhibited position-invariant adaptation, insofar as the magnitude of adaptation did not depend on whether stimuli were repeated in the same or opposite hemifields. In contrast, object-selective regions showed significantly greater adaptation when objects were repeated in the same hemifield. These results suggest that neuronal receptive fields (RFs) in scene-selective regions span the vertical meridian, whereas RFs in object-selective regions do not. The PPA, RSC, and TOS may support scene perception and navigation by maintaining stable representations of large-scale features of the visual environment that are insensitive to the shifts in retinal stimulation that occur frequently during natural vision.