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Categorical discrimination and target detection in visual search: An investigation using concurrent EEG and eye movement recordings

Damian Ariel Care

  • CABA,
  • Argentina
  • Damian Ariel Care ¹
  • , Bruno Bianchi ¹
  • , Juan Esteban Kamienkowski ¹
  • , Matias J. Ison ²
  • 1 Laboratorio de Inteligencia Artificial Aplicada (ICC, CONICET-UBA, Argentina)
  • 2 School of Psychology (University of Nottingham, UK)

Early access to visual information, like category, plays an important role in visual search. In particular, the N170 ERP component, a hallmark of face processing, emerges in the occipitotemporal cortex around 170 ms after stimulus onset with an increased amplitude to faces. Here, we aimed to study how its sensitivity to category information extents to a free viewing paradigm. We co-registered EEG and eye-tracking to investigate fixation related potentials to pictures of different categories during visual search. Participants were asked to search for one target from an array of faces and objects embedded in random noise. Firstly, we hypothesized that a larger N170 would be elicited by fixations to faces in comparison to objects. Secondly, based on a recently proposed framework [Kamienkowski et al., 2018], we hypothesized that EEG signatures underlying early target detection reflect saccade inhibition, and would, therefore, be activated differently for ‘hard’ distractors (same category as the target) than ‘easy’ distractors (different category). In this study, we show a stronger activation for fixations to faces than to objects. Consistent with our second hypothesis, we also found significant differences between components elicited by fixations to easy and hard distractors. These results generalize the characterization of the N170 to a wider range of experiments, and show specific category discrimination components potentially associated with eye movement guidance.