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Hector Rieiro, Maria Sanchez-Vives, Susana martinez-Conde, Jie Cui, Ramon Reig, Stephen Macknik; The neural basis of temporal brightness effects. Journal of Vision 2013;13(9):317. doi: https://doi.org/10.1167/13.9.317.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous research has shown, using human subjects, that the relationship of contrast perception to stimulus duration follows the Broca-Sulzer effect, in which the perceived contrast shows a peak at a specific range of stimulus durations, as opposed to Bloch’s Law, which predicts a monotonic relationship (Rieiro, et al. PNAS 2012). To determine the mechanistic pathways for this effect, we recorded from single units intracellularly and extracellularly in the primary visual cortex of cats and monkeys. We found in awake monkeys that the average response of neurons showed no (or little) change in the onset response, and that the after-discharge revealed an increase in magnitude followed by a decrease in magnitude of response that matched the Broca-Sulzer effect’s timing. To determine the underlying mechanisms of this effect, we found with intracellular recordings in cat that onset responses to contrast–sign-matched stimuli show an unremarkable effect of duration (in correspondence with the monkeys), but that the termination response for contrast-sign reversed stimuli matched the Broca-Sulzer effect. This suggests that cells that process a specific contrast-sign signal the turning on of a stimulus, whereas the responses in the reverse contrast sign cells indicate the termination of that stimulus. The current model of brightness is that on-cells code the whiteness of a stimulus whereas off-cells code the blackness: on-cells signal white whereas off-cells signal black. Our data reveal that, instead, on-cells signal the onset of white stimulus whereas off-cells signal the turning off of a white stimulus. Further our data reveals a completely novel model in which the temporal effects of brightness are derived by the magnitude of the reverse contrast-sign pathway.
Meeting abstract presented at VSS 2013
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