Contributions of low- and high-level contextual mechanisms to human face perception

Abstract

What we perceive is modulated by the context in which it appears. Contextual modulations are especially robust when processing upright face stimuli but are found throughout the human visual system. Face contextual modulations have been attributed to specialized (holistic) mechanisms implemented in high-level regions of the processing hierarchy. Here we examine their potential functional link to low-level contextual mechanisms, i.e. the relationship of contextual modulations between basic (contrast detection task) and complex (face) stimuli (eye matching task). Face stimuli were shown in upright and inverted orientations, to investigate the extent to which the neural specialization for upright faces influences the potential functional link between low- and high-level contextual mechanisms. Both the profile and magnitude of the contextual modulations correlated between inverted eye matching and contrast detection tasks. Neural specialization modulated this functional relationship as contextual modulation in upright eye matching and contrast detection tasks only correlated at the level of their profile suggesting the functional independence but the similar working principles of the mechanisms involved. The combined study of low- and high-level contextual modulations sheds new light on the functional relationship between the different levels of the visual processing hierarchy, and thus on its functional organization.