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Front Syst Neurosci. 2015 Sep 1;9:122. doi: 10.3389/fnsys.2015.00122. eCollection 2015.

Saccade-induced image motion cannot account for post-saccadic enhancement of visual processing in primate MST.

Author information

1
National Vision Research Institute, Australian College of Optometry Carlton, VIC, Australia ; Department of Optometry and Vision Sciences, Australian Research Council Centre of Excellence for Integrative Brain Function, University of Melbourne Parkville, VIC, Australia ; Department of Electrical and Electronic Engineering, University of Melbourne Parkville, VIC, Australia.
2
Department of Psychology and Neuroscience, Life Sciences Centre, Dalhousie University Halifax, NS, Canada.
3
Visual Sciences, Yerkes National Primate Research Center, Emory University Atlanta, GA, USA.
4
National Vision Research Institute, Australian College of Optometry Carlton, VIC, Australia ; Department of Optometry and Vision Sciences, Australian Research Council Centre of Excellence for Integrative Brain Function, University of Melbourne Parkville, VIC, Australia.

Abstract

Primates use saccadic eye movements to make gaze changes. In many visual areas, including the dorsal medial superior temporal area (MSTd) of macaques, neural responses to visual stimuli are reduced during saccades but enhanced afterwards. How does this enhancement arise-from an internal mechanism associated with saccade generation or through visual mechanisms activated by the saccade sweeping the image of the visual scene across the retina? Spontaneous activity in MSTd is elevated even after saccades made in darkness, suggesting a central mechanism for post-saccadic enhancement. However, based on the timing of this effect, it may arise from a different mechanism than occurs in normal vision. Like neural responses in MSTd, initial ocular following eye speed is enhanced after saccades, with evidence suggesting both internal and visually mediated mechanisms. Here we recorded from visual neurons in MSTd and measured responses to motion stimuli presented soon after saccades and soon after simulated saccades-saccade-like displacements of the background image during fixation. We found that neural responses in MSTd were enhanced when preceded by real saccades but not when preceded by simulated saccades. Furthermore, we also observed enhancement following real saccades made across a blank screen that generated no motion signal within the recorded neurons' receptive fields. We conclude that in MSTd the mechanism leading to post-saccadic enhancement has internal origins.

KEYWORDS:

electrophysiology; eye movements; macaque monkey; medial superior temporal area; ocular following; visual cortex

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