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Greg L. West, Adam A.K. Anderson, Susanne Ferber, Carson Pun, Jay Pratt; Electrophysiological evidence for biased competition in V1 favoring motivationally significant stimuli. Journal of Vision 2009;9(8):464. doi: https://doi.org/10.1167/9.8.464.
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© ARVO (1962-2015); The Authors (2016-present)
Conscious experience is selective: we are not aware of everything we see. So, how do some percepts reach conscious awareness while others do not? According to one influential model, stimuli will either be detected or go unnoticed based on the result of a competition for neural representation between multiple concurrent stimulus inputs. The winner of this competition will be selected for more detailed analyses.
The goal of this study was to use event-related potentials (ERPs) to investigate whether stimuli of motivational significance “win” this competition for neural representation in visual cortex. Specifically, we took advantage of the C1 component which, due to the architecture of the calcarine fissure in V1, evokes either a negative or positive potential when stimuli are displayed in either the upper or lower hemifields respectively. When stimuli in the upper hemifield receive greater neural representation as compared to those concurrently displayed the lower hemifield, activity will summate to produce a distinct negative C1 component. In a first experiment, we contrasted a pair of task irrelevant fearful faces and their Fourier transformed derivatives, displayed in opposite hemifields, while participants engaged in a central task. Results showed that when fearful faces were displayed in the upper hemifield (evoking a negative potential) and Fourier transformed faces were displayed in the lower hemifield (evoking a positive potential), activity summated to produce a negative C1 component. Importantly, when Fourier transformed faces were presented in the upper hemifield, the C1 component was eliminated. This pattern was replicated when contrasting fearful and neutral faces, and also with fearful faces and their inverted counterparts.
These findings demonstrate that (a) displays of threat competing for awareness are prioritized over other concurrent stimuli, and (b) this biased competition is resolved within 70 ms of visual processing; likely before any feed-back from higher level visual cortices occurs.
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