Relative alpha power did not differ at mirror-matched SEEG sites in 172 bilaterally implanted adults

This analysis tested whether relative alpha power differed between mirror-matched left and right stereoelectroencephalography (SEEG) bipolar pairs in adults with bilateral implants. It used archived 0.5 Hz spectra for 261 subjects from the RAM memory task: 60 seconds beginning at the first WORD event, with MNI coordinates for each pair. A preregistered, hashed plan selected subjects with at least three qualifying couples matched within 15 mm. In 172 subjects, mean left-minus-right relative 8–12.5 Hz power was +0.002 log10 (95% bootstrap CI −0.022 to +0.025; two-sided sign-flip p=0.88). This interval excludes a mean difference larger than about 6% in relative alpha power and lies inside the prespecified ±0.05 log10 margin. No band or tested region showed a lateralization; all secondary Holm-adjusted p values were 1.00. A correlation with implant laterality had rho=−0.196 and p=0.0099 before correction, but was not significant after Holm correction (p=0.079) and is not a finding about seizure onset. Results were similar in the reported matching and summary-statistic checks. The sample consisted of epilepsy patients aged about 18–64 years; seizure-onset contacts were not excluded, handedness was unavailable, and the analyzed segments came from a memory task rather than eyes-closed rest. MNI matching did not use anatomical labels or gray/white matter checks. The group analysis does not rule out individual asymmetries or test trait or mood correlates.

stereoelectroencephalography · SEEG · alpha power · hemispheric asymmetry · mirror matching · intracranial EEG · RAM memory task