Friston, K. J., Frith, C. D., Liddle, P. F., Dolan, R. J., Lammertsma, A. A., & Frackowiak, R. S. (1990). The relationship between global and local changes in PET scans. Journal of Cerebral Blood Flow & Metabolism, 10, 458-466. doi:10.1038/jcbfm.1990.88.