In 247 RAM SEEG patients, alpha/theta ratios were enriched near 1.9–2.0, not specifically at 2:1

We tested whether theta and alpha peak frequencies in the same SEEG bipolar pair favor the golden-mean ratio 1.618 or the 2:1 harmonic ratio. We analyzed archived 0.5 Hz spectra from 261 patients and 28,461 pairs in the RAM FR1 and catFR1 memory tasks. In 247 patients with at least five dual-peak pairs, the mean within-patient enrichment was -0.0067 near 1.618 (95% CI -0.0131 to -0.0003; Holm p=0.044) and +0.0162 near 2.0 (95% CI +0.0075 to +0.0247; Holm p=0.0010). The enrichment scan peaked at 1.92, close to the median patient ratio of 1.91, and theta and alpha frequencies were positively correlated within patients (mean Spearman rho=+0.104). Thus, ratios near 2:1 were more common than predicted by a within-patient shuffle, but the result does not show a preference for exactly 2:1; the golden-mean prediction was not supported. Frequency correlation or harmonics of non-sinusoidal rhythms could explain the enrichment. The analysis used 60 seconds from the start of a memory task in epilepsy patients, without a rest condition, and spectra alone cannot distinguish harmonics from coupled rhythms.

intracranial EEG · SEEG · theta · alpha · beta · peak frequency · frequency ratio · harmonics · memory task · within-patient shuffle