Suppression of displacement detection in the presence and absence of eye movements: a neuro-computational perspective

Abstract

Understanding the subjective experience of a visually stable world during eye movements has been an important research topic for many years. Various studies were conducted to reveal fundamental mechanisms of this phenomenon. For example, in the paradigm saccadic suppression of displacement (SSD), it has been observed that a small displacement of a saccade target could not easily be reported if this displacement took place during a saccade. New results from Zimmermann et al. (J Neurophysiol 112(12):3066-3076, 2014) show that the effect of being oblivious to small displacements occurs not only during saccades, but also if a mask is introduced while the target is displaced. We address the question of how neurons in the parietal cortex may be connected to each other to account for the SSD effect in experiments involving a saccade and equally well in the absence of an eye movement while perception is disrupted by a mask.

Saccadic Suppression of Displacement Does Not Reflect a Saccade-Specific Bias to Assume Stability

“…In line with this assumption, it has been shown that reducing the onset's strength by diminishing the target's contrast to the background reduces or even abolishes the positive effect of blanking during saccades [25]. Another possibility is that the blank interval puts the post-saccadic or post-mask stimulus outside a critical temporal window for accumulation or integration of position or motion information [30,31,42,43]. Zimmermann and colleagues [31] argue that precise encoding of the pre-jump target location takes some time.…”

“…Indeed, Gysen and colleagues [22] have found that the detection of trans-saccadic jumps is better for a moving than a stationary object, demonstrating that violations along a smooth, predictable motion trajectory can be detected more easily than simple jumps. It is important to note that many authors have acknowledged that displacement estimates during fixation and saccades could rely on different sources of information: Whereas motion information is suppressed during saccades, apparent motion, as well as position information, is available during fixation [6,16,25,33,42]. For instance, saccadic suppression of displacement in the model by Niemeier and colleagues [16] is not due to a saccade-specific setting for the prior, but occurs due to a combination of suppressed motion signals (i.e., sole reliance on position information) and the Bayesian prior for jumps: The poorer the sensory information (e.g., due to motion suppression) the greater the influence of the Bayesian prior.…”