Smooth pursuit eye movements and perception share target selection, but only some central resources

Smooth pursuit eye movements have been linked to perception by a common attentional mechanism. We investigated whether perceptual performance was traded for smooth pursuit performance. While tracking a red target cross, observers had to discriminate the orientation of a flashed peripheral grating. We manipulated the priority given to the two tasks. Pursuit gain changed according to observers' effort to pursue the target, but perceptual discrimination of the peripheral flash was not affected by these changes, suggesting that smooth pursuit does not use the same resources as perception. Complete resource sharing may be confined to situations involving multiple moving objects. Next, we added a second perceptual task on the foveal pursuit target. Foveal discrimination performance was traded for peripheral discrimination performance and pursuit gain followed the perceptual priorities. Thus, smooth pursuit gain is affected by which target has been selected for enhanced perceptual processing, but that does not imply shared perceptual resources. (C) 2009 Elsevier B.V. All rights reserved.