The effect of expertise upon behavioral and neural representational spaces

Abstract

When people become an expert in a particular domain, they process objects of expertise in a different manner. Previous neuroimaging studies have demonstrated how this expertise alters brain activity by comparing objects of expertise with other objects (e.g., Gauthier et al., 2000, Nature Neuroscience; Harel et al., 2010, Cerebral Cortex). However, everyone knows whether an image depicts a bird or a car. In contrast, only a bird expert can tell apart a great-tailed from a boat-tailed grackle. Here we focus upon the neural basis of expertise at this detailed level by comparing the similarities and differences of the representational spaces of birds between 20 ornithologists and 20 control participants. We scanned subjects with functional magnetic resonance imaging while presenting images of 24 different bird types. The image set was organized in 8 triplets, which each contained two birds that belonged to the same species but were visually different (e.g. male and female) and one bird that resembled one of the other two birds but belonged to a different species. As such, the triplets dissociated species-level semantics from visual similarity. Behaviorally, ornithologists showed more within-group consistency in subjective similarity ratings compared to controls. In addition, the ornithologists showed a sensitivity to the dissociation between species and visual appearance when rating semantic similarity. A neural representational similarity analysis analyzed the multi-voxel patterns in low-level visual cortex (LVC), high-level visual cortex (HVC), and prefrontal cortex (PFC). In PFC, the neural patterns distinguished bird types more reliably in ornithologists than in controls. In addition, the similarity structure of the neural patterns was more shared between ornithologists than between controls, in particular in HVC and in PFC. Overall, the fMRI findings suggest that expertise results in an overall expansion of the neural representational space of objects of expertise, but not in a qualitatively different organization. Meeting abstract presented at VSS 2018