Mirror-matched contralateral SEEG pairs show greater within-patient spectral-shape similarity than distance-matched pairs

In archived RAM stereo-EEG recordings from 256 patients, we compared spectral-shape similarity between mirror-matched contralateral bipolar pairs and contralateral control pairs matched for direct distance. We analyzed a 60 s segment from the first word event, removed each pair's mean log power across frequency, and subtracted a leave-one-subject-out Gaussian group map at its MNI location. Among 136 patients with at least three eligible matched left pairs and at least one control, the patient-level difference in mean Fisher-z similarity was 0.172 (95% bootstrap CI 0.119–0.223); 79% had a positive difference (two-sided sign-flip p<0.001; dz=0.56). Results remained positive without map removal, with a 5 mm matching radius, and in a 4–30 Hz band (Holm-adjusted p<0.001 for each). Residual similarity decreased smoothly with mirror distance. A cross-patient mirror comparison was much smaller (mean difference 0.010, 95% CI 0.004–0.016; p=0.001). These findings support a patient-specific bilateral spectral signature beyond the group location map. They do not establish its cause or clinical utility. The analysis uses one task segment per patient, has no tissue labels, and cannot exclude effects of patient-specific tissue mix at mirror sites. Similarity varied as a spatial gradient rather than a strict homotopic peak.

stereo-EEG · SEEG · spectral shape · homotopic similarity · interhemispheric · RAM · MNI · bipolar pairs · intracranial EEG