Experimental design and interpretation of functional neuroimaging studies of cognitive processes

This article discusses how the relation between experimental and baseline conditions in functional neuroimaging studies affects the conclusions that can be drawn from a study about the neural correlates of components of the cognitive system and about the nature and organization of those components. I argue that certain designs in common use--in particular the contrast of qualitatively different representations that are processed at parallel stages of a functional architecture--can never identify the neural basis of a cognitive operation and have limited use in providing information about the nature of cognitive systems. Other types of designs-such as ones that contrast representations that are computed in immediately sequential processing steps and ones that contrast qualitatively similar representations that are parametrically related within a single processing stage-are more easily interpreted.