Measuring implicit line orientation discrimination using fast periodic visual stimulation

The fast periodic visual stimulation oddball paradigm (FPVS-oddball) is an electroencephalography (EEG) marker of discrimination between two classes of frequency tagged stimuli (standards and oddballs). Here, we probe low-level visual function using FPVS-oddball, with a view to its future use as a sensitive diagnostic marker of visuoperceptual cognitive impairment. Thirty participants (21 (±5) years, 7 males) completed five FPVS-oddball conditions that implicitly measured their ability to discriminate an oddball line orientation (1°,5°,10°,30°,80°), from a standard vertical line, as well as an equiprobable control condition. Twenty-four participants (24 (±5) years, 5 males) completed a retest session around one month later. Following 100s of recording, activity at the oddball presentation frequency, a neural signal of discrimination between standard and oddball stimuli, was observed in response to lines of 5° and above. The magnitude of this oddball response increased as oddball lines deviated more from vertical. Demonstrating consistency in individual participants, oddball responses were present in 30/30 participants in response to a deviation of 30° and 29/30 in response to a deviation of 80°. At larger deviations, oddball responses were highly reliable between sessions, measured using intraclass correlations. Overall, this study showed that FPVS-oddball can consistently and reliably measure line orientation discrimination in individual participants. The consistency and reliability of oddball responses in the cognitively healthy, could provide a strong baseline that clinical group's performance could be compared to, guiding neurocognitive assessment.