L.H.Snyder*; B.M.Lawrence
Washington Univ. Sch. Med, St Louis, MO, USA
The FEF is traditionally thought to be highly specific for eye movements, but recent research has suggested that this may be true of only a subset of FEF neurons. The activity of FEF movement cells does appear to be tightly coupled to saccade initiation (Hanes & Schall, 1996), but activity in FEF visual cells can be evoked by distractors to which no saccade is directed (Murthy et al., 2001). The notion of two subpopulations of cells, one tightly linked to saccade production and the other reflecting the locus of spatial attention, is consistent with the finding that FEF micro-stimulation can either drive saccadic eye movements or produce attention-like modulations in V4 cells (Moore & Armstrong, 2003).

Inconsistent with this view, we previously reported that visual, but not movement cells, are preferentially activated by the instruction to prepare a saccade relative to a reach (Lawrence & Snyder, 2002). This preference was observed in the absence of spatial information. It is possible that, in the presence of spatial information, visual neurons may lose their effector specificity and reflect only the locus of spatial attention. To test this, we recorded from FEF neurons in a delayed movement paradigm, in which both effector and spatial information were present.

Consistent with our previous results, we found that most visual cells with memory activity coded both spatial and effector information during the delay period. We call these combination cells. Their activity cannot be explained as a correlate of spatial attention: activity was higher during the delay period of saccade compared to reach trials, even when the movement was directed outside the response field. (Most movement cells were non-responsive during the delay period, and therefore coded neither effector nor space.) These results are inconsistent with a generic role of visual neurons in spatial attention. Rather, the present results suggest that a subset of visual neurons process spatial information in an effector-dependent manner.
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L.H. Snyder, B.M. Lawrence. CODING OF EFFECTOR AND SPACE IN MONKEY FRONTAL EYE FIELDS (FEF). Program No. 441.1. 2003 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2003. Online.