# Neuronal mechanisms of cortical processing in early vision

> **NIH NIH R01** · STATE COLLEGE OF OPTOMETRY · 2021 · $392,850

## Abstract

PROJECT SUMMARY
Visual information is transferred from the eye to the brain through ON and OFF pathways that signal the
presence of light and dark features in visual scenes. ON and OFF pathways are present in all animals with
image-forming visual-systems including flies and primates, however, we still have a poor understanding of how
they interact in visual processing. While neuroscience textbooks describe ON and OFF pathways as sharing
equal cortical space, recent work has demonstrated that the OFF pathway greatly dominates cortical
responses. We hypothesize that this cortical OFF dominance originates from a difference in the contrast
response function between ON and OFF pathways that we recently discovered. Because contrast saturation is
more pronounced within the ON pathway, light stimuli are spatially distorted and less effective at driving
cortical responses than dark stimuli, which causes the cortex to be OFF dominated. Because of this greater
spatial distortion for lights, we predict that ON/OFF differences in contrast saturation will have major
implications not only in cortical function but also in human visual perception and visual disease. Therefore, this
proposal uses the differences in ON/OFF contrast saturation as a conceptual framework to predict and
investigate how cortical OFF dominance changes under different stimulation conditions and the implications of
these changes for the perception of lights and darks. Our conceptual framework predicts that cortical OFF
dominance will increase when the image is out of focus either because of normal changes in lens
accommodation (e.g. blurred background when fixating a target at close distance) or visual disease (e.g.
amblyopia, myopia). In turn, cortical OFF dominance will decrease when seeing high spatial frequencies with
high mean luminance, which are common outdoors. To test our predictions and investigate the dynamics of
ON and OFF cortical function, we will measure the responses of cortical single neurons to dark and light
targets under a large variety of stimulus conditions (e.g. different contrasts, spatial frequency, mean luminance,
luminance distribution). We will then use the same stimulus conditions to measure changes in light/dark visual
acuity and visual salience in humans. To fully characterize cortical responses of single neurons to multiple
stimulus dimensions, we will use an innovative multielectrode array that we have been developing over the
past years to record from well-isolated single neurons for prolonged periods of time. This novel technical
approach allows us to obtain an unprecedented characterization of the stimulus space that modulates ON/OFF
signaling by testing a large combination of stimulus conditions that could not be fully explored with previous
methods.

## Key facts

- **NIH application ID:** 10119286
- **Project number:** 5R01EY027361-05
- **Recipient organization:** STATE COLLEGE OF OPTOMETRY
- **Principal Investigator:** Jose Manuel Alonso
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $392,850
- **Award type:** 5
- **Project period:** 2017-03-01 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10119286

## Citation

> US National Institutes of Health, RePORTER application 10119286, Neuronal mechanisms of cortical processing in early vision (5R01EY027361-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10119286. Licensed CC0.

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