The motion aftereffect: more than area V5/MT? Evidence from O-15-butanol PET studies

The motion aftereffect is a perceptual phenomenon which has been extensivel y investigated both psychologically and physiologically. Neuroimaging techn iques have recently demonstrated that area V5/MT is activated during the pe rception of this illusion. The aim of this study was to test the hypothesis if a more broadly distributed network of brain regions subserves the motio n aftereffect. To identify the neuronal structures involved in the percepti on of the motion aftereffect, regional cerebral blood flow (rCBF) measureme nts with positron emission tomography were performed in six normal voluntee rs. Data were analysed using SPM96. The motion-sensitive visual ureas inclu ding area V5/MT were activated in both hemispheres. Additionally, the later al parietal cortex bilaterally, the right dorsolateral prefrontal cortex, t he anterior cingulate cortex and the left cerebellum showed significant inc reases in rCBF values during the experience of the waterfall illusion. In a further reference condition with identical attentional demand but no perce ption of a motion aftereffect elevated rCBF were found in these regions as well. In conclusion, our findings support the notion that the perceptual il lusion of motion arises exclusively in the motion-sensitive visual area V5/ MT. In addition, a more widespread network of brain regions including the p refrontal and parietal cortex is activated during the waterfall illusion wh ich represents a non-motion aftereffect-specific subset of brain areas but is involved in more basic attentional processing and cognition. (C) 2001 El sevier Science B.V. All rights reserved.