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Jeroen van Boxtel; Attention and consciousness exhibit different gain functions in afterimage experiments. Journal of Vision 2016;16(12):17. doi: https://doi.org/10.1167/16.12.17.
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© ARVO (1962-2015); The Authors (2016-present)
The link between attention and consciousness is fiercely debated, and it is not yet known whether they operate through similar, or widely different mechanisms. The influences of attention and consciousness on sensory processing can be described as modulations of a baseline response function, and are called gain modulations or gain functions. We derived behavioural contrast response curves, by measuring afterimage durations for a range of inducer stimulus contrasts. Attention was manipulated by asking the participants to perform a distracting rapid serial visual presentation task. Conscious perception was manipulated by showing (or not showing) an interocular mask. We found that, overall, afterimage durations increase with increasing contrast. We further show that attention decreases afterimage durations, and operates through a response-gain function. Conversely, consciousness increases afterimage durations, and operates through a contrast-gain function. To obtain a better mechanistic insight, we fitted various versions of a hierarchical normalization model to the data, and compared the fit quality of these models using the Bayesian Information Criterion. This analysis showed that the best model required 2 levels, with the consciousness manipulation modulating the first level, and attention modulating the second level. These results demonstrate that attention and consciousness exhibit different types of gain control, and enter the normalization process at different processing levels. Our results disprove the intuitive idea that attention and consciousness are always tightly entwined, and advocate for careful control of parameters that influence attention and consciousness in future research.
Meeting abstract presented at VSS 2016
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