Real-life visual tasks such as tracking jumping objects and scanning visual scenes often require a sequence of saccadic eye movements. The ability of the ocular motor system to parallel process saccades has been previously demonstrated. We recorded the monocular eye movements of five normal human subjects using the magnetic search coil technique in a double step paradigm. Initial target jumps were always purely horizontal or purely vertical. We were interested in the latency to onset of the second saccade as a function of direction in relation to the first saccade. When the inter stimulus interval (ISI) was 150 or 180 ms orthogonal second saccades were of significantly shorter latency than second co-linear saccades. When the ISI was 250 ms the latencies of orthogonal and co-linear second saccades were statistically indistinguishable. Based on these findings it is postulated that the ocular motor system can more readily co-process orthogonal than co-linear saccades.
Bibliographical noteFunding Information:
Acknowledgements This research was partially funded by a grant from the German-Israel Foundation for Scientific Research and Development (GIF) (CRG and AZZ) and a grant from the Christians for Israel Chair in Medical Research at Bar Ilan University (AZZ). We wish to thank Smadar Shatz (Bar-Ilan University Computer Center) for help with Matlab programming. We thank Dr Nicholas Port for research assistance.
- Eye movement
- Parallel processing