Corollary Discharge Contributes To Perceived Eye Location In Monkeys 1 2 3

Acknowledgements: We thank Thérèse Collins for emphasizing the importance of the 32 saccade error analysis and two reviewers whose insightful criticisms improved the paper. We 33 are grateful to Altah Nichols and Tom Ruffner for machine shop support. Supported by the 34 ABSTRACT 37 In spite of saccades changing the image on the retina several times per second, we still 38 perceive a stable visual world. A possible mechanism underlying this stability is that an internal 39 retinotopic map is updated with each saccade, with the location of objects being compared 40 before and after the saccade. Psychophysical experiments have shown that humans derive 41 such location information from a corollary discharge (CD) accompanying saccades. Such a CD 42 has been identified in the monkey brain in a circuit extending from superior colliculus to frontal 43 cortex. There is a missing piece, however. Perceptual localization is established only in 44 humans, and the CD circuit only in monkeys. We therefore extended measurement of 45 perceptual localization to the monkey by adapting the target displacement detection task 46 developed in humans. During saccades to targets, the target disappeared and then 47 reappeared, sometimes at a different location. The monkeys reported the displacement 48 direction. Detections of displacement were similar in monkeys and humans, but enhanced 49 detection of displacement from blanking the target at the end of the saccade was observed only 50 in humans, not in monkeys. Saccade amplitude varied across trials, but the monkey's estimates 51 of target location did not follow that variation, indicating that eye location depended on an 52 internal CD rather than external visual information. We conclude that monkeys use a CD to 53 determine their new eye location after each saccade, just as humans do.