Detecting faces in pure noise images: a functional MRI study on top-down perception

Abstract

To assess the nature of top-down perceptual processes without contamination from bottom-up input, this functional MRI study investigated face detection in pure noise images. Greater activation was revealed for face versus nonface responses in the fusiform face area, but not in the occipital face area. Across participants, positive correlations were found for the degree of greater face-detection activation between the fusiform face area and bilateral inferior frontal gyri, suggesting a top-down pathway generating perceptual expectations. In contrast, the medial frontal, parietal, supplementary motor, parahippocampal, and striatal areas produced negative correlations between degrees of greater face-detection activation and behavioral responses, suggesting a possible role for these areas in selecting and executing appropriate responses that are based on the top-down expectations.

Face recognition under ambiguous visual stimulation: fMRI correlates of “encoding styles”

“…In the absence of strong top-down guidance by, for example, expectations or selective attention, a reliable object categorization of these ambiguous stimuli might be more strongly driven by the application of primary schemata as represented in object sensitive visual areas. Studies on object categorization of ambiguous stimuli in the absence of top-down control demonstrated a relation between activation in extrastriate object sensitive regions with the individual categorization behavior [Akrami et al, 2009;Li et al, 2009;Liu and Jagadeesh, 2008;Sterzer and Kleinschmidt, 2007;Summerfield et al, 2006b;Zhang et al, 2008]. However, besides stimulus properties top-down control is the second important factor during percept formation and top-down control is quite often represented in frontal brain regions.…”

“…For example, object selective regions are active during task instructions to simply imagine specific objects for which these brain regions are sensitive without any sensory stimulation [O'Craven and Kanwisher, 2000]. In the presence of ambiguous sensory stimulation, such as ambiguous [Summerfield et al, 2006a,b] or random noise images [Li et al, 2009;Zhang et al, 2008], frontal brain regions seem to enhance signals in extrastriate object sensitive regions that match the object category predicted by task instructions. Such task instructions might involve to selectively attend one of two superimposed objects [O'Craven et al, 1999].…”

“…However, these secondary schemata seem to be more transient in nature, but might, similar to primary schemata, figure as template against which incoming information is compared. Secondary schemata seem to originate predominantly in frontal brain regions and modulate the information flow and categorization processes in extrastriate visual processing regions [Fenske et al, 2006;Li et al, 2009;Summerfield et al, 2006a,b;Zhang et al, 2008], whereby the orbito-frontal cortex (OFC) in particular seems to signal subjectively successful object categorization [Fenske et al, 2006;Summerfield and Koechlin, 2008].…”

“…However, besides stimulus properties top-down control is the second important factor during percept formation and top-down control is quite often represented in frontal brain regions. Top-down control by secondary schemata could be generated by context-related expectations [Fenske et al, 2006;Kveraga et al, 2007a] or by task instructions [Li et al, 2009;Zhang et al, 2008], and this top-down influence might affect the bottom-up processing and primary schema application in extra-striate brain regions. For example, object selective regions are active during task instructions to simply imagine specific objects for which these brain regions are sensitive without any sensory stimulation [O'Craven and Kanwisher, 2000].…”

“…However, visual object recognition is not only affected by this bottom-up processing but also by top-down modulations. Such top-down processes are imposed, for example, by selectively attending to a specific stimulus or stimulus feature [Banich et al, 2000], expectations about the occurrence of specific objects [Li et al, 2009;Zhang et al, 2008], predictions about forthcoming objects [Fenske et al, 2006;Summerfield and Egner, 2009], or the monitoring of decision processes under uncertainty conditions [Ridderinkhof et al, 2004]. This higher level top-down modulation might facilitate the processing of attended, expected, or predicted objects though this facilitation might be based on different underlying brain mechanisms, such that attention might enhance and expectation might reduce visual processing in extrastriate object sensitive brain regions [see Summerfield and Egner, 2009].…”