Cortical mechanisms of visual brightness

• Authors: Reece Mazade, Emory University; Jianzhong Jin, SUNY College of Optometry; Hamed Rahimi-Nasrabadi, SUNY College of Optometry; Sohrab Najafian, SUNY College of Optometry; Carmen Pons, SUNY College of Optometry; JM Alonso, SUNY College of Optometry
• Journal Title: Cell Reports
• Volume: Volume 40, Number 13
• Publisher: Elsevier | 2022-09-27
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1016/j.celrep.2022.111438
• Subjects: Engineering, Biomedical
• Keywords: brightness

Abstract

The primary visual cortex signals the onset of light and dark stimuli with ON and OFF cortical pathways. Here, we demonstrate that both pathways generate similar response increments to large homogeneous surfaces and their response average increases with surface brightness. We show that, in cat visual cortex, response dominance from ON or OFF pathways is bimodally distributed when stimuli are smaller than one receptive field center but unimodally distributed when they are larger. Moreover, whereas small bright stimuli drive opposite responses from ON and OFF pathways (increased versus suppressed activity), large bright surfaces drive similar response increments. We show that this size-brightness relation emerges because strong illumination increases the size of light surfaces in nature and both ON and OFF cortical neurons receive input from ON thalamic pathways. We conclude that visual scenes are perceived as brighter when the average response increments from ON and OFF cortical pathways become stronger.