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Jon Guez, Adam Morris, Bart Krekelberg; Internal Noise Mechanisms of Intra-Saccadic Suppression. Journal of Vision 2012;12(9):1237. doi: 10.1167/12.9.1237.
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Despite the fast and frequent eye movements that we make – and the resulting, self-induced motion that our eyes receive – our perception of the world remains stable. A decrease in visual sensitivity measured just before and during saccades – termed saccadic suppression – is thought to underlie this perceptual phenomenon. Our goal was to quantify the behavioral phenomenon of saccadic suppression using a formal signal detection model and use this to infer neural mechanisms of saccadic suppression. We employed the Perceptual Template Model (PTM) that relates visual detection to three distinct internal processing mechanisms. The first increases uncertainty about the stimulus; the second adds stimulus-dependent noise to the system; the third adds stimulus-independent noise to the system. We measured contrast thresholds for horizontal gratings flashed for one frame (8 ms) during fixation and during saccades, allowing us to quantify intra-saccadic suppression. We varied the amount of noise in the stimulus. The resulting threshold-versus-noise (TVN) data were used to fit the PTM, separately for fixation and saccade conditions. A comparison of the parameters in the two models allowed us to determine which mechanisms were necessary to account for intra-saccadic suppression. We found that intra-saccadic suppression decreased as external noise increased for low levels of external noise – consistent with a gain reduction mechanism. However, at high external noise levels, suppression remained constant – consistent with stimulus-dependent noise injection. It has previously been shown that saccadic suppression for stimuli presented just before the saccade can be described by a reduction in gain only (Watson & Krekelberg, J Neurosci 2011). Our current results suggest that this mechanism also applies for stimuli presented during a saccade, but that in addition, a source of multiplicative noise reduces the visibility of intra-saccadic stimuli. This quantification serves as a constraint on putative neural mechanisms of saccadic suppression.
Meeting abstract presented at VSS 2012
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