Evaluating functional localizers: The case of the FFA

Abstract

Functional localizers are routinely used in neuroimaging studies to test hypotheses about the function of specific brain areas. The specific tasks and stimuli used to localize particular regions vary widely from study to study even when the same cortical region is targeted. Thus, it is important to ask whether task and stimulus changes lead to differences in localization or whether localization procedures are largely immune to differences in tasks and contrasting stimuli. We present two experiments and a literature review that explore whether face localizer tasks yield differential localization in the fusiform gyrus as a function of task and contrasting stimuli. We tested standard localization tasks---passive viewing, 1-back, and 2-back memory tests---and did not find differences in localization based on task. We did, however, find differences in the extent, strength and patterns/reliabilities of the activation in the fusiform gyrus based on comparison stimuli (faces vs. houses compared to faces vs. scrambled stimuli).

Intra- and interhemispheric connectivity between face-selective regions in the human brain

“…The locations of the core face-processing regions (FFA, OFA, and STS) were consistent with those described in previous studies (Andrews and Ewbank 2004;Berman et al 2010;Downing et al 2006;Fox et al 2009;Hoffman and Haxby 2000;Kanwisher et al 1997). We also found significant face selectivity in the right IFG (see also Chan and Downing 2011;Scalaidhe et al 1999;Tsao et al 2008;Vignal et al 2000) and the right IPS.…”

“…Although many studies have shown that regions in the core system are face selective, it is not clear whether all regions in the extended system are face selective or are merely recruited by the face-processing system (Berman et al 2010;Ishai 2008;Wiggett and Downing 2008). Our second objective was to determine how these face-selective regions are connected.…”

High-resolution imaging of expertise reveals reliable object selectivity in the fusiform face area related to perceptual performance

“…Despite the similarity of the patterns for car expertise and face responses in the right hemisphere, it should be kept in mind that the face localizer and the correlation map were acquired at different resolutions and that one represents a simple contrast but the other captures variance in neural activity related to individual differences in a discrimination task. Defining the peak FFA based on a functional localizer has proven robust to differences in task difficulty or contrast categories for the FFA (33), but this appears less likely in other regions. Future work comparing correlations with expertise for faces to that of objects in a sample with sufficient variability in behavioral face performance (32) could better test the similarity of these networks.…”

Direct Structural Connections between Voice- and Face-Recognition Areas

“…2C) was used to localize the FFA with the standard contrast visual "face stimuli versus object stimuli" (Kanwisher et al, 1997). By combining an object (a mobile phone) and human hand in the control stimulus, we used a combination of stimuli frequently used in FFA localizers (Kanwisher et al, 1997;Fox et al, 2009;Berman et al, 2010). These two conditions were embedded in a more complex experiment that was designed to address a different research question.…”