Abstract

The oculomotor system can initiate remarkably accurate saccades towards moving targets (interceptive saccades) the processing of which is still under debate. The generation of these saccades requires the oculomotor centers to have information about the motion parameters of the target that then must be extrapolated to bridge the inherent processing delays. We investigated to what degree the information about motion of a saccade target is available in the lateral intra-parietal area (area LIP) of macaque monkeys for generation of accurate interceptive saccades. When a multi-layer neural network was trained based on neural discharges from area LIP around the time of saccades towards stationary targets, it was also able to predict the end points of saccades directed towards moving targets. This prediction, however, lagged behind the actual post-saccadic position of the moving target by ~ 80 ms when the whole neuronal sample of 105 neurons was used. We further found that single neurons differentially code for the motion of the target. Selecting neurons with the strongest representation of target motion reduced this lag to ~ 30 ms which represents the position of the moving target approximately at the onset of the interceptive saccade. We conclude that—similarly to recent findings from the Superior Colliculus (Goffart et al. J Neurophysiol 118(5):2890–2901)—there is a continuum of contributions of individual LIP neurons to the accuracy of interceptive saccades. A contribution of other gaze control centers (like the cerebellum or the frontal eye field) that further increase the saccadic accuracy is, however, likely.

Highlights

  • Visual tracking of a moving object is achieved by combinations of saccades that bring the image of the object of interest onto the fovea and smooth pursuit eye movements that slowly follow a once foveated target

  • To confirm the expected effect of target motion on saccadic eye movements, we investigated the end points of saccades towards targets moving from the center of the screen in eight different directions

  • The results demonstrate that the motion of the stimulus exhibited a clear influence on the end-positions of the interceptive saccades

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Summary

Introduction

Visual tracking of a moving object is achieved by combinations of saccades that bring the image of the object of interest onto the fovea and smooth pursuit eye movements that slowly follow a once foveated target. Saccades towards moving targets were shown to be remarkably accurate (Fuchs 1967; Cassanello et al 2008; Fleuriet and Goffart 2012) This performance of the saccadic system is striking since it must be able to extrapolate the motion trajectory of the target to account for its own processing time before saccade onset (typically 100–300 ms) as well as for the duration of. Brain Structure and Function (2021) 226:2707–2723 generation of the motion-related component of interceptive saccades. Beside these findings about the role of sub-cortical areas in processing of interceptive saccades, cortical contributions along the dorsal visual pathway are little investigated yet. Target motionrelated signals were reported in the Frontal eye field (Barborica and Ferrera 2003; Xiao et al 2007; Ferrera and Barborica 2010) that receives input from the cortical motion areas (Tian and Lynch 1996) and has direct efferent connections to the SC (Segraves and Goldberg 1987; Stanton et al 1988) and to the oculomotor areas in the brain stem (Schiller et al 1980)

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