Spatial Resolution Evaluation Based on Experienced Visual Categories With Sweep Evoked Periodic EEG Activity.

PURPOSE: Visual function is typically evaluated in clinical settings with visual acuity (VA), a test requiring to behaviorally match or name optotypes such as tumbling E or Snellen letters. The ability to recognize these symbols has little in common with the automatic and rapid visual recognition of socially important stimuli in real life. Here we use sweep visual evoked potentials to assess spatial resolution objectively based on the recognition of human faces and written words.

METHODS: To this end, we tested unfamiliar face individuation1 and visual word recognition2 in 15 normally sighted adult volunteers with a 68-electrode electroencephalogram system.

RESULTS: Unlike previous measures of low-level visual function including VA, the most sensitive electrode was found at an electrode different from Oz in a majority of participants. Thresholds until which faces and words could be recognized were evaluated at the most sensitive electrode defined individually for each participant. Word recognition thresholds corresponded with the VA level expected from normally sighted participants, and even a VA significantly higher than expected from normally sighted individuals for a few participants.

CONCLUSIONS: Spatial resolution can be evaluated based on high-level stimuli encountered in day-to-day life, such as faces or written words with sweep visual evoked potentials.