Vase or Face? A Neural Correlate of Shape-Selective Grouping Processes in the Human Brain

Abstract

Recent neuroimaging studies have described a differential activation pattern associated with specific object images (e.g., face-related and building-related activation) in human occipito-temporal cortex. However, it is as yet unclear to what extent this selectivity is due to differences in the statistics of local object features present in the different object categories, and to what extent it reflects holistic grouping processes operating across the entire object image. To resolve this question it is essential to use images in which identical sets of local features elicit the perception of different object categories. The classic Rubin vase-face illusion provides an excellent experimental set to test this question. In the illusion, the same local contours lead to the perception of different objects (vase or face). Here we employed a modified Rubin vase-face illusion to explore to what extent the activation in face-related regions is attributable to the presence of local face features, or is due to a more holistic grouping process that involves the entire face figure. Biasing cues (gratings and color) were used to control the perceptual state of the observer. We found enhanced activation in face-related regions during the "face profile" perceptual state compared to the "vase" perceptual state. Control images ruled out the involvement of the biasing cues in the effect. Thus, object-selective activation in human face-related regions entails global grouping processes that go beyond the local processing of stimulus features.

Spontaneous local variations in ongoing neural activity bias perceptual decisions

“…2A). This result is in line with previous findings from sustained presentation of the Rubin ambiguity (11,14,15), where perception is bistable and periods of face dominance are associated with greater FFA activity.Confirming our critical hypothesis, we also found a significant right-FFA activity difference of similar magnitude to the stimulus-related effect already present in immediate prestimulus periods and thus related to neural activity several seconds before (Fig. 2 A).…”

Neural correlates of human action observation in hearing and deaf subjects

“…It is interesting that this particular left hemisphere region has been observed in studies of visual object processing, including decisions regarding face versus object properties (Gerlach et al, 2000;Levy et al, 2001;Hasson et al, 2001). In the context of the present study, these findings are consistent with engagement of a visual posterior lateral system that is involved in the assessments of visual properties of action stimuli that may be engaged for the differentiation of non-linguistic human action in deaf individuals.…”

Autism and the development of face processing

“…Fourth, FFA responses are modulated by changes in facial features and configuration [139]. Fifth, the adult FFA is correlated with detection, categorization and identification of faces, but not nonface objects [10,11,136,138]. In contrast, activations of face-selective regions in the STS do not correlate with recognition performance [11].…”

“…Second, neuroimaging methods have revealedspecific face-selective regions in the fusiform gyrus, namely the ''FFA'' [7]. Third, FFA responses to vaguely face-like stimuli correlate with the subjective experience of face perception [8,[136][137][138], suggesting that the FFA responds to the face gestalt. Fourth, FFA responses are modulated by changes in facial features and configuration [139].…”