Nonspatial Saccade-Specific Activation in area LIP of Monkey Parietal Cortex

Department of Anatomy and Neurobiology, McDonnell Center for Higher Brain Function, Washington University School of Medicine, St. Louis, Missouri 63110 Submitted 10 October 2002; accepted in final form 3 June 2003 We present evidence that neurons in the lateral intraparietal area (LIP) of monkey posterior parietal cortex (PPC) are activated by the instruction to make an eye movement, even in the complete absence of a spatial target. This study employed a visually guided motor task that dissociated the type of movement to make (saccade or reach) from the location where the movement was to be made. Using this task, animals were instructed to prepare a specific type of movement prior to knowing the spatial location of the movement target. We found that 25% of the LIP neurons recorded in two animals were activated significantly more by the instruction to prepare a saccade than by the instruction to prepare a reach. This finding indicates that LIP is involved in more than merely spatial attention and provides further evidence for nonspatial effector-specific signal processing in the dorsal stream. Address for reprint requests and other correspondence: L. H. Snyder (E-mail: larry{at}eye-hand.wustl.edu ).