Fast Periodic Visual Stimulation EEG as an implicit measure for perceptual discrimination and categorization of mid-level objects.

Abstract

How do we organize and process incoming visual information on a daily basis? Perceptual categorization and discrimination are essential to interact efficiently with the surrounding world. However, these implicit and automatic processes are typically investigated explicitly, allowing for decisional or motivational biases. The present project investigates whether Fast Periodic Visual Stimulation (FPVS) during scalp EEG can provide an implicit neural marker of perceptual categorization and discrimination. In FPVS, visual stimulation of the brain at a constant frequency rate leads to an EEG response at that exact frequency. The detection of periodically introduced oddball images in a series of base images will be signaled by an EEG response at the oddball frequency, which makes it an objective and implicit measure for change detection. FPVS paradigms have been validated in the context of low-level (e.g. contrast sensitivity) as well as higher-level (face) processing, but not yet for perceptual discrimination and categorization of mid-level objects. In a first experiment (n=8), we showed that the FPVS base-oddball paradigm offers a reliable neural signature of categorical perception while systematically “sweeping” through morph series of visual objects (e.g. peacock-truck and church-duck). In a second experiment (n=8), we confirmed that the FPVS base-oddball paradigm can implicitly measure reduced discrimination for exemplars within a category and enhanced discrimination across the category boundary in the same morph series. Both experiments suggest that FPVS EEG can provide reliable neural measures for categorization and discrimination, and correlations with behavioral measures suggest an association with behavioral sensitivity. Next, we will collect data on 14 participants performing both the discrimination and categorization experiment implicitly and explicitly and look at correlations between these measures. Furthermore, we will investigate whether the combination of these measures can shed more light on individual differences in perceptual processing along particular personality traits, e.g. autism-quotient.