Contrast adaptation and representation in human early visual cortex

Abstract

SummaryThe human visual system can distinguish variations in image contrast over a much larger range than measurements of the static relationship between contrast and response in visual cortex would suggest. This discrepancy may be explained if adaptation serves to recenter contrast response functions around the ambient contrast, yet experiments on humans have yet to report such an effect. By using eventrelated fMRI and a data-driven analysis approach, we found that contrast response functions in V1, V2 and V3 shift to approximately center on the adapting contrast. Furthermore, we discovered that unlike earlier areas, human V4 (hV4) responds positively to contrast changes regardless of the sign, suggesting that hV4 is sensitive to the salience of the change rather than faithfully representing contrast. These findings suggest that the visual system discounts slow uninformative changes in contrast with adaptation, yet remains exquisitely sensitive to changes that may signal important events in the environment.

Colour fluctuations in grapheme‐colour synaesthesia: The effect of clinical and non‐clinical mood changes

“…It is possible therefore that differences in emotional processing induced by mood changes have direct influences on visual, and other perceptual functions. Alternatively, we might consider instead one area in particular in visual cortex, V4, which has been directly implicated in synaesthetic colours (e.g., Hubbard, Arman, Ramachandran, & Boynton, 2005), but has also been linked to the feature of contrast gain (Gardner et al, 2005). We saw above that contrast gain is altered in depressive mood states (Bubl et al, 2009(Bubl et al, , 2010.…”

An encoding model of temporal processing in human visual cortex

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“…S4). (ii) Adaptation would have resulted in declining responses during long trials of continuous presentation of a single stimulus42 . However, we observed negligible adaptation in early (e.g.…”

Large-scale Dynamics of Perceptual Decision Information across Human Cortex

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