Whole person-evoked fMRI activity patterns in human fusiform gyrus are accurately modeled by a linear combination of face- and body-evoked activity patterns

Abstract

Visual cues from the face and the body provide information about another's identity, emotional state, and intentions. Previous neuroimaging studies that investigated neural responses to (bodiless) faces and (headless) bodies have reported overlapping face- and body-selective brain regions in right fusiform gyrus (FG). In daily life, however, faces and bodies are typically perceived together and are effortlessly integrated into the percept of a whole person, raising the possibility that neural responses to whole persons are qualitatively different than responses to isolated faces and bodies. The present study used fMRI to examine how FG activity in response to a whole person relates to activity in response to the same face and body but presented in isolation. Using multivoxel pattern analysis, we modeled person-evoked response patterns in right FG through a linear combination of face- and body-evoked response patterns. We found that these synthetic patterns were able to accurately approximate the response patterns to whole persons, with face and body patterns each adding unique information to the response patterns evoked by whole person stimuli. These results suggest that whole person responses in FG primarily arise from the coactivation of independent face- and body-selective neural populations.

Whole-agent selectivity within the macaque face-processing system

“…The subadditive and additive responses align with the prevailing view that face patches consist of category-selective neurons; unadulterated face-selective neurons would lead to the former and a mix of selective face and body neurons would lead to the latter. These responses were largely expected, because viewing multiple objects commonly evokes subadditive or additive fMRI signals (25)(26)(27), and previous studies of face-body integration in the human face areas have found responses in this subadditive to additive range (22,28,29). The superadditive fMRI signals in the anterior patches, however, are a surprising finding, at odds with the idea that these areas are strictly domainspecific.…”

Interobject grouping facilitates visual awareness

“…The representation of physical (e.g., geometrical) relationships among simple stimuli, such as those leading to the formation of illusory contours, seems to rely on both early visual cortical areas and higher-level ventral stream areas (e.g., Abu Bakar, Liu, Conci, Elliott, & Ioannides, 2008;Stanley & Rubin, 2003;von der Heydt, Peterhans, & Baumgartner, 1984), whereas the representation of object-object relations likely involves only higher occipitotemporal object processing areas (Kim & Biederman, 2010;Roberts & Humphreys, 2010). Distributed patterns of activity in these areas evoked by two objects can be modeled as a linear combination of the response patterns to the individual objects (MacEvoy & Epstein, 2009;Reddy, Kanwisher, & VanRullen, 2009) and the relative weighting of the two patterns seems to be altered when the two objects form meaningful spatial relationships (Baeck, Wagemans, & Op de Beeck, 2013; but see also Kaiser, Strnad, Seidl, Kastner, & Peelen, 2014), indicating that these object configurations are represented in visual cortex activity patterns. Furthermore, Kanizsa-type figures do not only induce the perception of illusory contours but also of an illusory surface, which constitutes a salient region that ''pops out'' in visual search (Davis & Driver, 1994;Gurnsey, Poirier, & Gascon, 1996).…”

Task influences pattern discriminability for faces and bodies in ventral occipitotemporal cortex

“…In this region of overlap, a univariate analytic approach revealed no significant difference in their mean activations. These findings indicate that the category-selectivity of neural responses can be defined at a finer resolution than can be easily examined in conventional univariate analysis (Downing, Wiggett, & Peelen, 2007; Kaiser, Strnad, Seidl, Kastner, & Peelen, 2014; Weiner & Grill-Spector, 2010). …”