Abstract
It is now reasonably well established that microsaccades (MS) enhance visual perception, although the underlying neuronal mechanisms are unclear. Here, using numerical simulations, we show that MSs enable efficient synchrony-based coding among the primate retinal ganglion cells (RGC). First, using a jerking contrast edge as stimulus, we demonstrate a qualitative change in the RGC responses: synchronous firing, with a precision in the 10 ms range, only occurs at high speed and high contrast. MSs appear to be sufficiently fast to be able reach the synchronous regime. Conversely, the other kinds of fixational eye movements known as tremor and drift both hardly synchronize RGCs because of a too weak amplitude and a too slow speed respectively. Then, under natural image stimulation, we find that each MS causes certain RGCs to fire synchronously, namely those whose receptive fields contain contrast edges after the MS. The emitted synchronous spike volley thus rapidly transmits the most salient edges of the stimulus, which often constitute the most crucial information. We demonstrate that the readout could be done rapidly by simple coincidence-detector neurons without knowledge of the MS landing time, and that the required connectivity could emerge spontaneously with spike timing-dependent plasticity.
Highlights
It is reasonably well established that microsaccades (MS) enhance visual perception, the underlying neuronal mechanisms are unclear
They found that in the turtle retina, a 5 Hz periodic movement with an amplitude of about one photoreceptor width caused the retinal ganglion cell (RGC) with receptive fields (RF) located along contrast edges to synchronize[10]
We modeled the foveal region of a primate retina and only included the midget cells, which represent about 95% of the foveal RGCs21
Summary
It is reasonably well established that microsaccades (MS) enhance visual perception, the underlying neuronal mechanisms are unclear. To the best of our knowledge, Greschner and colleagues are the only ones who have studied the relationship between FEM and RGC synchrony[10] They found that in the turtle retina, a 5 Hz periodic movement with an amplitude of about one photoreceptor width caused the RGCs with receptive fields (RF) located along contrast edges to synchronize[10]. These movements, are quite different from MSs in primates, which, as previously stated, occur more rarely (once or twice per second), at irregular intervals, and rapidly carry the retinal image over much longer distances. Using numerical simulations, we show that the MSs, being in the proper range of speed and amplitude, are sufficient to synchronize a small subset of RGCs, namely those that are strongly activated by the image www.nature.com/scientificreports/
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