Seeing via Miniature Eye Movements: A Dynamic Hypothesis for Vision

Abstract

During natural viewing, the eyes are never still. Even during fixation, miniature movements of the eyes move the retinal image across tens of foveal photoreceptors. Most theories of vision implicitly assume that the visual system ignores these movements and somehow overcomes the resulting smearing. However, evidence has accumulated to indicate that fixational eye movements cannot be ignored by the visual system if fine spatial details are to be resolved. We argue that the only way the visual system can achieve its high resolution given its fixational movements is by seeing via these movements. Seeing via eye movements also eliminates the instability of the image, which would be induced by them otherwise. Here we present a hypothesis for vision, in which coarse details are spatially encoded in gaze-related coordinates, and fine spatial details are temporally encoded in relative retinal coordinates. The temporal encoding presented here achieves its highest resolution by encoding along the elongated axes of simple-cell receptive fields and not across these axes as suggested by spatial models of vision. According to our hypothesis, fine details of shape are encoded by inter-receptor temporal phases, texture by instantaneous intra-burst rates of individual receptors, and motion by inter-burst temporal frequencies. We further describe the ability of the visual system to readout the encoded information and recode it internally. We show how reading out of retinal signals can be facilitated by neuronal phase-locked loops (NPLLs), which lock to the retinal jitter; this locking enables recoding of motion information and temporal framing of shape and texture processing. A possible implementation of this locking-and-recoding process by specific thalamocortical loops is suggested. Overall it is suggested that high-acuity vision is based primarily on temporal mechanisms of the sort presented here and low-acuity vision is based primarily on spatial mechanisms.

Physical emission of spatially‐modulated radar

“…From an 'energy on target' perspective and in light of the small perturbations observed for fixational eye movement [16][17][18], it seems likely that one would wish K to be relatively small (perhaps ≤1). Using (4) and (8), the outermost elements scale the electrical angle phase change by the largest value of (M − 1)/2 so that, based on (22), the total electrical angle phase change at these elements when traversing K null-to-null spatial intervals is…”

“…1) via slow movements known as drift and rapid movements known as microsaccades [15][16][17]. While the purpose of these fixational eye movements has long been debated and remains an open research topic, the current consensus is that these small, spatial perturbations improve visual acuity because the associated transients enhance contrast and sensitivity as well as aiding in the resolving of spatial ambiguities.…”

Catching the voltage gradient—asymmetric boost of cortical spread generates motion signals across visual cortex: a brief review with special thanks to Amiram Grinvald

“…On the one hand, the emergence of motion streaks appears undesirable for sensation and indeed, mechanisms exist to suppress them. 60,[63][64][65] In contrast, it has been shown that information about motion axes is still present across neuronal activity and can be extracted from motion streaks. [66][67][68][69][70] Thus, motion streaks may be analyzed unconsciously and separately over time [71][72][73][74] to contribute to further analysis such as form-from-motion at higher processing stages.…”

A Model for Visual Perception and Recognition of Outlines

“…The simplest approach, possibly, is to use transient responses -lateral inhibition seems more complex. The method of Ahissar & Arieli (2001, 2012 would be suitable, namely onset times of bursts of "spikes"; here "temporal encoding" is not used, so the outline representation would be the occurrence of the first spike at a particular position.…”

“…A major difference is that geons are invariant with viewpoint, whereas here viewpoint invariance is obtained using attentional planes; a feature of Biederman's theory that is used here is that stored representations are in two dimensions. Ahissar & Arieli (2001, 2012 used spatial coding for coarse, absolute positions, and temporal coding for fine detail using relative positions. That approach for positions is used here, except that relative positions, in the form of traces, are from spatial distributions; traces are used down to a size of area of attention of 20' radius, approximately -they are not suitable for "vernier acuity", i.e.…”