1. S. Kastner, P. De Weerd, L. G. Ungerleider, Laboratory of Brain & Cognition, National Institute of Mental Health (NIMH), National Institutes of Health (NIH), Building 49, Room 1B80, Bethesda, MD 20892–4415, USA. R. Desimone, Laboratory of Neuropsychology, NIMH, NIH, Bethesda, MD 20892, USA.