Journal of Neurophysiology, Vol 76, Issue 6 3617-3632, Copyright © 1996 by APS

ARTICLES

Saccades to remembered targets: the effects of smooth pursuit and illusory stimulus motion

A. Z. Zivotofsky, K. G. Rottach, L. Averbuch-Heller, A. A. Kori, C. W. Thomas, L. F. Dell'Osso and R. J. Leigh
Department of Neurology, Case Western Reserve University, Cleveland, Ohio 44106, USA.

1. Measurements were made in four normal human subjects of the accuracy of saccades to remembered locations of targets that were flashed on a 20 x 30 deg random dot display that was either stationary or moving horizontally and sinusoidally at +/-9 deg at 0.3 Hz. During the interval between the target flash and the memory-guided saccade, the "memory period" (1.4 s), subjects either fixated a stationary spot or pursued a spot moving vertically sinusoidally at +/-9 deg at 0.3 Hz. 2. When saccades were made toward the location of targets previously flashed on a stationary background as subjects fixated the stationary spot, median saccadic error was 0.93 deg horizontally and 1.1 deg vertically. These errors were greater than for saccades to visible targets, which had median values of 0.59 deg horizontally and 0.60 deg vertically. 3. When targets were flashed as subjects smoothly pursued a spot that moved vertically across the stationary background, median saccadic error was 1.1 deg horizontally and 1.2 deg vertically, thus being of similar accuracy to when targets were flashed during fixation. In addition, the vertical component of the memory-guided saccade was much more closely correlated with the "spatial error" than with the "retinal error"; this indicated that, when programming the saccade, the brain had taken into account eye movements that occurred during the memory period. 4. When saccades were made to targets flashed during attempted fixation of a stationary spot on a horizontally moving background, a condition that produces a weak Duncker-type illusion of horizontal movement of the primary target, median saccadic error increased horizontally to 3.2 deg but was 1.1 deg vertically. 5. When targets were flashed as subjects smoothly pursued a spot that moved vertically on the horizontally moving background, a condition that induces a strong illusion of diagonal target motion, median saccadic error was 4.0 deg horizontally and 1.5 deg vertically; thus the horizontal error was greater than under any other experimental condition. 6. In most trials, the initial saccade to the remembered target was followed by additional saccades while the subject was still in darkness. These secondary saccades, which were executed in the absence of visual feedback, brought the eye closer to the target location. During paradigms involving horizontal background movement, these corrections were more prominent horizontally than vertically. 7. Further measurements were made in two subjects to determine whether inaccuracy of memory-guided saccades, in the horizontal plane, was due to mislocalization at the time that the target flashed, misrepresentation of the trajectory of the pursuit eye movement during the memory period, or both. 8. The magnitude of the saccadic error, both with and without corrections made in darkness, was mislocalized by approximately 30% of the displacement of the background at the time that the target flashed. The magnitude of the saccadic error also was influenced by net movement of the background during the memory period, corresponding to approximately 25% of net background movement for the initial saccade and approximately 13% for the final eye position achieved in darkness. 9. We formulated simple linear models to test specific hypotheses about which combinations of signals best describe the observed saccadic amplitudes. We tested the possibilities that the brain made an accurate memory of target location and a reliable representation of the eye movement during the memory period, or that one or both of these was corrupted by the illusory visual stimulus. Our data were best accounted for by a model in which both the working memory of target location and the internal representation of the horizontal eye movements were corrupted by the illusory visual stimulus. We conclude that extraretinal signals played only a minor role, in comparison with visual estimates of the direction of gaze, in planning eye movements to remembered targ

This article has been cited by other articles:

				A. A. Thompson and D. Y. P. Henriques Updating Visual Memory Across Eye Movements for Ocular and Arm Motor Control J Neurophysiol, November 1, 2008; 100(5): 2507 - 2514. [Abstract] [Full Text] [PDF]

				E. J. Schlicht and P. R. Schrater Impact of Coordinate Transformation Uncertainty on Human Sensorimotor Control J Neurophysiol, June 1, 2007; 97(6): 4203 - 4214. [Abstract] [Full Text] [PDF]

				M. Wei, N. Li, S. D. Newlands, J. D. Dickman, and D. E. Angelaki Deficits and Recovery in Visuospatial Memory During Head Motion After Bilateral Labyrinthine Lesion J Neurophysiol, September 1, 2006; 96(3): 1676 - 1682. [Abstract] [Full Text] [PDF]

				A. Z. Zivotofsky, M. E. Goldberg, and K. D. Powell Rhesus Monkeys Behave As If They Perceive the Duncker Illusion J. Cogn. Neurosci., July 1, 2005; 17(7): 1011 - 1017. [Abstract] [Full Text] [PDF]

				E. M. Klier, D. E. Angelaki, and B. J. M. Hess Roles of Gravitational Cues and Efference Copy Signals in the Rotational Updating of Memory Saccades J Neurophysiol, July 1, 2005; 94(1): 468 - 478. [Abstract] [Full Text] [PDF]

				N. Li, M. Wei, and D. E. Angelaki Primate Memory Saccade Amplitude After Intervened Motion Depends on Target Distance J Neurophysiol, July 1, 2005; 94(1): 722 - 733. [Abstract] [Full Text] [PDF]

				M. Tanaka Involvement of the Central Thalamus in the Control of Smooth Pursuit Eye Movements J. Neurosci., June 22, 2005; 25(25): 5866 - 5876. [Abstract] [Full Text] [PDF]

				N. Saijo, I. Murakami, S. Nishida, and H. Gomi Large-Field Visual Motion Directly Induces an Involuntary Rapid Manual Following Response J. Neurosci., May 18, 2005; 25(20): 4941 - 4951. [Abstract] [Full Text] [PDF]

				L. Li, B. T. Sweet, and L. S. Stone Effect of Contrast on the Active Control of a Moving Line J Neurophysiol, May 1, 2005; 93(5): 2873 - 2886. [Abstract] [Full Text] [PDF]

				G. Blohm, M. Missal, and P. Lefevre Processing of Retinal and Extraretinal Signals for Memory-Guided Saccades During Smooth Pursuit J Neurophysiol, March 1, 2005; 93(3): 1510 - 1522. [Abstract] [Full Text] [PDF]

				A. Z. Zivotofsky The Duncker Illusion: Intersubject Variability, Brief Exposure, and the Role of Eye Movements in Its Generation Invest. Ophthalmol. Vis. Sci., August 1, 2004; 45(8): 2867 - 2872. [Abstract] [Full Text] [PDF]

				T. M. Herter and D. Guitton Accurate bidirectional saccade control by a single hemicortex Brain, June 1, 2004; 127(6): 1393 - 1402. [Abstract] [Full Text] [PDF]

				J. T. Baker, T. M. Harper, and L. H. Snyder Spatial Memory Following Shifts of Gaze. I. Saccades to Memorized World-Fixed and Gaze-Fixed Targets J Neurophysiol, May 1, 2003; 89(5): 2564 - 2576. [Abstract] [Full Text] [PDF]

				J. F. Soechting, K. C. Engel, and M. Flanders The Duncker Illusion and Eye-Hand Coordination J Neurophysiol, February 1, 2001; 85(2): 843 - 854. [Abstract] [Full Text] [PDF]

				J. T. Somers, V. E. Das, L. F. Dell'Osso, and R. J. Leigh Saccades to Sounds: Effects of Tracking Illusory Visual Stimuli J Neurophysiol, July 1, 2000; 84(1): 96 - 101. [Abstract] [Full Text] [PDF]

				T. M. Herter and D. Guitton Human Head-Free Gaze Saccades to Targets Flashed Before Gaze-Pursuit Are Spatially Accurate J Neurophysiol, November 1, 1998; 80(5): 2785 - 2789. [Abstract] [Full Text] [PDF]

				W. P. Medendorp, M. A. Smith, D. B. Tweed, and J. D. Crawford Rotational Remapping in Human Spatial Memory during Eye and Head Motion J. Neurosci., January 1, 2002; 22(1): RC196 - RC196. [Abstract] [Full Text] [PDF]