Interaction envelope: Local spatial representations of objects at all scales in scene-selective regions

Abstract

While several cortical regions have been highlighted for their category selectivity (e.g., scene-selective regions like the parahippocampal place area, object selective regions like the lateral occipital complex), a growing trend in cognitive neuroscience has been to investigate what particular perceptual properties these regions calculate. Classical scene-selective regions have been particularly targeted in recent work as being sensitive to object size or other related properties. Here we test to which extent these regions are sensitive to spatial information of stimuli at any size. We introduce the spatial object property of "interaction envelope," defined as the space through which a user transverses to interact with an object. In two functional magnetic resonance imaging experiments, we examined activity in a comprehensive set of perceptual regions of interest for when human participants viewed object images varying along the dimensions of interaction envelope and physical size. Importantly, we controlled for confounding perceptual and semantic object properties. We find that scene-selective regions are in fact sensitive to object interaction envelope for small, manipulable objects regardless of real-world size and task. Meanwhile, small-scale entity regions maintain selectivity to stimulus physical size. These results indicate that regions traditionally associated with scene processing may not be solely sensitive to larger object and scene information, but instead are calculating local spatial information of objects and scenes of all sizes.

Keywords: Interaction envelope; Parahippocampal place area; Scene-selective regions; Spatial object properties; fMRI.

Fig. 1

All 320 stimuli used in the fMRI experiments, grouped by condition. The first overarching analysis of the study contrasts activity for small versus big objects, but the main manipulation can be seen in the 2-factor design of the small objects, covarying physical size with interaction envelope size.

Fig. 2

ROI analysis of percent signal change for viewing objects of small scale versus large scale. Regions are grouped based on whether they are more selective for larger entities (in blue: PPA, OPA, Big ROIs, RSC), smaller entities (in red: left Small ROIs, left LOS),or neither (LOC, FFA, EBA). Asterisks indicate significant differences in a paired t-test (all p < 0.005), and error bars indicate standard error of the mean.

Fig. 3

A chart of percent signal change for the ROI analysis in the Main Experiment. ROI graphs are grouped as in Fig. 2, with ROIs with selectivity to large entities in blue, ROIs for smaller entities in red, and other ROIs in gray. Error bars indicate standard error of the mean. Stars indicate a significant effect of interaction envelope, diamonds indicate a significant effect of physical size, and the star within the diamond indicates a significant effect of the statistical interaction of the factors. Significance was determined at a level of p < 0.05. For each ROI, the highlighted symbol is the effect with the higher effect size.

Fig. 4

A random-effects whole brain analysis (N = 16). (Top) F-maps (a sagittal and coronal view) for a repeated-measures 2-way ANOVA, showing voxels with a significant main effect (p < 0.005 uncorrected) for interaction envelope (blue) and physical size (red). (Bottom) T-maps for general linear models on the conditions. The intercorrelated condition map (left) shows the contrast of significant activation (p < 0.005 uncorrected) for objects of both small physical size and envelope (red—no voxels emerge) versus objects of both large physical size and envelope (blue). The orthogonalized conditions map (right) shows the contrast of significant activation of the other two conditions where size and interaction envelope are not correlated—small physical size and large envelope size (blue) versus large physical size and small envelope size (red—no voxels emerge).

Fig. 5

A chart of percent signal change for each ROI in the Control Experiment, where participants are asked to attend to the size of each object while performing a 1-back task. This graph is read in the same way as Fig. 2.