After harmonic removal, high frequency power followed photic flicker on few SEEG pairs in one patient

In one Mayo Clinic patient with stereoelectroencephalography (SEEG), we compared voltage and 70–170 Hz high frequency band (HFB) power during clinical photic flicker from 3 to 30 Hz across 154 bipolar pairs. Raw HFB envelopes showed 2–13 pairs above z > 3.1 at 3–20 Hz, including extreme right anterior occipital (RAO) values without a voltage response. Removing flicker harmonics reduced these RAO values to control levels. Across 3–20 Hz, the harmonic-removed pair-level check found 25 hits with eyes open and 21 with eyes closed, compared with leave-one-out null counts of 15.9 and 17.1. Most hits were on the right lingual ROC shaft, which contained 8% of pairs. Voltage responses were more frequent than HFB responses, and no signal responded at 30 Hz. The findings suggest that, in this patient, non-phase-locked HFB followed flicker on only a few pairs. Periodic artifact can produce apparent raw HFB following; voltage at the stimulus frequency and its second harmonic was the stronger feature for frequency-tagged SEEG BCI. Interpretation is limited by one patient and train per frequency and eye condition, dependent pairs, six control trains, no multiple-comparison correction, possible filter metadata error, and possible photic artifact.

stereoelectroencephalography · photic flicker · high frequency band · harmonic removal · steady-state response · brain-computer interface · signal artifact