Abstract
Abstract: :
Purpose: Recent studies from this laboratory have demonstrated that the physiologically-identified pursuit eye movement region of the frontal eye field (FEF) in Cebus monkeys sends dense projections to both the caudate and putamen. The caudate nucleus has been studied extensively in its role in controlling saccadic eye movements (Hikosaka et al., Physiological Reviews, 2000, for review) but only a few studies implicate the basal ganglia in the control of pursuit eye movements (e.g., O'Driscoll et al., Neuroreport, 2000). We have injected anterogradely-transported tracers in the functionally-identified pursuit subregion (FEFsem) and saccade subregion (FEFsac) of the frontal eye field. We then used a three-dimensional rendering program to create a virtual model of the labeled terminal fields. The model can be rotated or expanded in order to provide a clearer understanding of the relationship between the labeled terminal fields than traditional illustration methods can provide. Methods: Electrical microstimulation was used to localize the FEFsem and FEFsac FEF in 4 Cebus apella monkeys. Small injections of BDA were made and the distributions of labeled axon terminals plotted using a light microscope and an image analysis system. We used a commercial software package (Rhinoceros; Robert McNeel and Associates) to generate the virtual model and then used PhotoPaint (Corel) to develop animated video images. Results: Terminal fields originating in the FEFsem occupied sharply-delimited zones in the caudate and putamen; those originating in the FEFsac were similar in density and over-all area, but did not overlap very much with the FEFsem fields. This relationship is clearly demonstrated by the virtual model. An animated version of this model will be displayed at the poster. Conclusion: These results suggest that the striatum may play an important role in the control of visual pursuit eye movements. The results also support the hypothesis of Alexander and Strick (e.g., Hoover et al., J. Neurosci., 1999) that the cortical-basal ganglia loop circuits for different functional modalities occupy discrete, highly segregated pathways.
Keywords: 409 eye movements: saccades and pursuits • 495 ocular motor control • 315 anatomy