Fusiform activation to animals is driven by the process, not the stimulus.
Previous studies have found that the lateral posterior fusiform gyri respond more robustly to pictures of animals than pictures of manmade objects and suggested that these regions encode the visual properties characteristic of animals. We suggest that such effects actually reflect processing demands arising when items with similar representations must be finely discriminated. In a positron emission tomography (PET) study of category verification with colored photographs of animals and vehicles, there was robust animal-specific activation in the lateral posterior fusiform gyri when stimuli were categorized at an intermediate level of specificity (e.g., dog or car). However, when the same photographs were categorized at a more specific level (e.g., Labrador or BMW), these regions responded equally strongly to animals and vehicles. We conclude that the lateral posterior fusiform does not encode domain-specific representations of animals or visual properties characteristic of animals. Instead, these regions are strongly activated whenever an item must be discriminated from many close visual or semantic competitors. Apparent category effects arise because, at an intermediate level of specificity, animals have more visual and semantic competitors than do artifacts.
Rogers
Timothy T
TT
MRC Cognition and Brain Sciences, Cambridge, UK. ttrogers@wisc.edu
Hocking
Julia
J
Mechelli
Andrea
A
Patterson
Karalyn
K
Price
Cathy
C
D000328:Adult; D000704:Analysis of Variance; D000818:Animals; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology*; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D012680:Sensitivity and Specificity; D013647:Task Performance and Analysis