A normalized contrast-encoding model exhibits bright/dark asymmetries similar to early visual neurons

Abstract

Biological sensory systems share a number of organizing principles. One such principle is the formation of parallel streams. In the visual system, information about bright and dark features is largely conveyed via two separate streams: the ON and OFF pathways. While brightness and darkness can be considered symmetric and opposite forms of visual contrast, the response properties of cells in the ON and OFF pathways are decidedly asymmetric. Here, we ask whether a simple contrast‐encoding model predicts asymmetries for brights and darks that are similar to the asymmetries found in the ON and OFF pathways. Importantly, this model does not include any explicit differences in how the visual system represents brights and darks, but it does include a common normalization mechanism. The phenomena captured by the model include (1) nonlinear contrast response functions, (2) greater nonlinearities in the responses to darks, and (3) larger responses to dark contrasts. We report a direct, quantitative comparison between these model predictions and previously published electrophysiological measurements from the retina and thalamus (guinea pig and cat, respectively). This work suggests that the simple computation of visual contrast may account for a range of early visual processing nonlinearities. Assessing explicit models of sensory representations is essential for understanding which features of neuronal activity these models can and cannot predict, and for investigating how early computations may reverberate through the sensory pathways.

Image luminance changes contrast sensitivity in visual cortex

“…ON-OFF contrast asymmetries are likely to be inherited in part from the retina ( Cooper, 2016 ; Kremkow et al, 2014 ) and may depend on parameters that we did not investigate such as spatial frequency ( Jansen et al, 2019 ; Kremkow et al, 2014 ; Onat et al, 2011 ), visual eccentricity, and brain state ( Azimi et al, 2020 ). There is increasingly stronger evidence that ON and OFF pathways remain cortically segregated ( Kremkow and Alonso, 2018 ) and operate relatively independently.…”

Different contrast encoding in ON and OFF visual pathways

“…Those observations were however mostly based on light increments. It is now well established that cone responses to light increments and decrements are asymmetric: the depolarization following a dark flash is larger in amplitude than the hyperpolarization following a bright flash of same magnitude from the background (defined as absolute difference) (Baden et al, 2013; Clark et al, 2013; Cooper, 2016). It is therefore likely that the mechanisms underlying different contrast representations in ON and OFF RGCs start already at the level of cones.…”

A Research on Automation Diagonsis of Pattern Recognition in Stained HEP-2 Cells

“…In order to attain the intensity level, green fluorescence is preferred. [4] The cell images are first transformed to grayscale by considering green channel. The lowest intensity at the bottom set to 1% of pixel values and highest intensity also with 1% of pixel value.…”

“…The calculations are done for background level in order to accomplish cellular signal and control the gain and camera offset. Cooper et al [4] Proposed an approach to encounter brightness of spatial variations through sequential antagonistic and this outcome is split by the local average luminance by nonlinear normalization. This work used standard deviation to determine the shapes through spatial extension over which contrast is computed.…”