Increased Activation in the Fusiform Face Area to Greebles is a Result of Expertise Training, Not by its Face-likeness

Abstract

In 2011, Brants, Wagemans, & Op de Beeck (JOCN 23:12, pp. 3949-3958) trained eight individuals to become Greeble experts, and found neuronal inversion effects [NIEs; i.e., higher Fusiform Face Area (FFA) activity for upright, rather than inverted Greebles]. These effects were also found for faces, both before and after training. By claiming to have replicated the seminal Greeble training study (i.e., Gauthier, Tarr, Anderson, Skudlarski, & Gore, 1999, Nat Neurosci, 2, 568-573), Brants et al. interpreted these results as participants viewing Greebles as faces throughout training, contrary to the original argument of subjects becoming Greeble experts only after training. However, such a claim presents two issues. First, the behavioral training results of Brants et al. did not replicate those of Gauthier et al (1999), raising concerns of whether the right training regime had been adopted. Second, both a literature review and meta-analysis of NIE in the FFA suggest its unreliability as an index of face(-like) processing. To empirically evaluate these issues, the present study compared two documented training paradigms (i.e., Gauthier & Tarr, 1997, Vision Res, 37, 1673-1682; and Gauthier, Williams, Tarr, & Tanaka, 1998, Vision Res, 38, 2401-2428) and explored their impact on the FFA. The results showed significant increases in the FFA for Greebles, and a clear neural "adaptation" (i.e., decreased activity for faces following Greebles, but not following non-face objects, in the FFA) both only in the Gauthier97 group, and only after training, reflecting clear modulation of expertise following "appropriate" training. In both groups, no clear NIE for faces nor Greebles were found. Collectively, these data invalidate the two assumptions behind the Brants et al. findings, and provide not only the updated support, but also the new evidence, for the perceptual expertise hypothesis of FFA.