September 2019
Volume 19, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2019
Neural correlates of target enhancement
Author Affiliations & Notes
  • Janir R da Cruz
    Laboratory of Psychophysics, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
    Institute for Systems and Robotics – Lisbon (LARSys) and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
  • Ophélie Favrod
    Laboratory of Psychophysics, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
  • Phillip R Johnston
    Rotman Research Institute of Baycrest Centre, University of Toronto, Toronto, Canada
  • Patrícia Figueiredo
    Institute for Systems and Robotics – Lisbon (LARSys) and Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal
  • Michael H Herzog
    Laboratory of Psychophysics, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
Journal of Vision September 2019, Vol.19, 273a. doi:https://doi.org/10.1167/19.10.273a
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      Janir R da Cruz, Ophélie Favrod, Phillip R Johnston, Patrícia Figueiredo, Michael H Herzog; Neural correlates of target enhancement. Journal of Vision 2019;19(10):273a. doi: https://doi.org/10.1167/19.10.273a.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

When a task-relevant stimulus is presented for a brief duration or with low contrast, neural enhancement is needed to boost the weak responses to the target. Otherwise, the stimulus goes unnoticed, which is the default when the stimulus is task-irrelevant. Here, we used evoked-related potentials (ERPs) to investigate the neural mechanisms of target enhancement. The target consisted of a vernier, i.e., two vertical bars that are slightly offset in the horizontal direction. Observers discriminated the offset direction. First, we compared the ERPs elicited by the vernier when it was task-relevant vs. task-irrelevant. When the vernier was task-relevant, it elicited strong ERPs amplitudes at ~200ms after stimulus-onset with a bilateral negative occipital and positive fronto-central topography. This topography remained stable for around 140ms. When the vernier was task-irrelevant, similar ERPs were elicited but with much weaker amplitudes and for shorter topography durations. In a second experiment, we presented a mask after the target vernier, with varying inter-stimulus-intervals (ISIs). Performance on the target decreased linearly with the ISI, i.e., the shorter the ISI, the worse the performance. Interestingly, the ERPs amplitudes and topography durations decreased with the ISI. When the ISI was 0ms, performance was at chance level and ERPs amplitudes and topography durations were very similar to when the vernier was task-irrelevant. We propose that invisibility can come by either task irrelevance or masking. Under these two conditions, ERPs amplitudes and topographies are identical, suggesting similar brain processing.

Acknowledgement: This work was partially funded by the Fundação para a Ciência e a Tecnologia under grant FCT PD/BD/105785/2014 and the National Centre of Competence in Research (NCCR) Synapsy (The Synaptic Basis of Mental Diseases) under grant 51NF40-158776. 
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