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Rimona Weil, Nicholas Furl, Christian Ruff, Ben Seymour, Guillaume Flandin, Ray Dolan, Jon Driver, Geraint Rees; Reward facilitates hemodynamic responses in higher visual areas. Journal of Vision 2009;9(8):862. doi: 10.1167/9.8.862.
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© ARVO (1962-2015); The Authors (2016-present)
The availability of financial reward can influence performance on tasks requiring visual discrimination, but the neural mechanisms giving rise to such changes in behavior remain unclear. In particular, whether reward has a direct or modulatory influence on visual processing remains uncertain.
Here, using functional magnetic resonance imaging, we investigated such possible effects of reward on visual judgements and activity in human visual cortex. Participants discriminated the orientation of two achromatic gratings presented successively in one visual field, while ignoring gratings presented to the other visual field. They received financial reward for each correct judgement at trial end. Critically, our event-related fMRI design allowed us to distinguish BOLD signals associated with visual stimulation by the gratings from those attributable to reward feedback, which was given audibly after a variable delay at trial end, when no visual stimuli were being presented.
We found a dissociation in responses in visual cortices between direct and modulatory effects of reward. While higher visual areas showed bilateral activation on trials when reward was given, compared to when no reward was given, no effect of reward was observed on earlier retinotopic levels of visual representation. In contrast, correct performance that was financially rewarded led to lateralised modulation of activity on the subsequent trial in retinotopic representations of the visual stimulus in primary visual cortex. Thus our findings demonstrate not only that visual cortex is modulated by reward, but that the effects of reward differ in early retinotopic and higher visual areas.
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