New research from a team of researchers at Vanderbilt University, part of the Temporal Dynamics Learning Center supported by NSF, used functional magnetic resonance imaging (fMRI) to study the structural correlates of face and object recognition ability. Prior work had shown that perceptual experts, such as car aficionados, have more activity in their visual system when they look at objects in their expert category.
The new work reveals that experts also have thicker gray matter in a critical part of the brain that is called the fusiform face area (FFA) and is known to be important for face recognition. A surprising finding of this work is that while people with a thicker FFA performed better with vehicles, it was those with a thinner FFA who performed better with faces and living objects.
This research offers important insights into the role of the FFA in visual perception and visual memory. Together with prior functional effects in FFA, the findings demonstrate that this region is important beyond faces, for non-face object processing. This structural effect of expertise has an interesting advantage over the more standard functional expertise effects: it could lead to a relatively faster accumulation of evidence across different labs, because a relatively quick behavioral test to measure object recognition ability can be easily administered, after the fact, to subjects who participated in any fMRI study that localized the FFA (see McGugin, R.W., Richler, J.J., Herzmann, G., Speegle, M. & Gauthier, I. 2012. The Vanderbilt Expertise Test Reveals Domain-General and Domain-Specific Sex Effects in Object Recognition. Vision Research, 69:10-22).
The FFA is defined by its selectivity for faces. Several studies have shown that the response of FFA to non-face objects can predict behavioral performance for these objects. However, one possible explanation of such results is that experts pay more attention to objects in their domain of expertise, driving signals up. The new work shows an effect of expertise with non-face objects in FFA that cannot be explained by differential attention. The team measured cortical thickness in functionally-defined regions in a group of men who varied in their expertise effects for cars in FFA. While subjects with a thicker FFA cortex performed better with vehicles, those with a thinner FFA cortex performed better with faces and living objects. The results point to a domain-general role of FFA in object perception and reveal an interesting double dissociation that does not contrast faces and objects, but rather living and non-living objects.
McGugin, R.W., Van Gulick, A.E. & Gauthier, I. (submitted). Cortical thickness in fusiform face area predicts face and object recognition performance.