Authors:

ROGERS, T. T., Hocking, J., Mechelli, A., PATTERSON, K. and Price, C

Reference:

Year of publication:

2005

CBU number:

5882

Abstract:

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 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 PET study of category-verification with coloured photographs of animals and vehicles, there was robust animal-specific activation in the lateral posterior fusiform gyri when stimuli were categorised at an intermediate level of specificity (e.g. dog or car); but when the same photographs were categorised 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 artefacts.