Anterior sites showed less alpha relative to theta in 191 RAM patients, while peak-frequency gradients were small and sensitive to location controls

A pre-registered replication tested two anterior-posterior spectral gradients reported in 42 RAM FR1 patients, using archived 60 s task-start spectra at 0.5 Hz resolution from 191 independent patients: 121 ds004789 FR1 and 70 ds004809 catFR1. Across patients, the alpha-minus-theta residual gradient (7-12 Hz minus 3-5.5 Hz) replicated (mean Spearman rho with MNI y = -0.325, 95% CI [-0.366, -0.285], 166/191 negative, Holm p = 1e-4). It remained in both tasks, after control for |x| and z, and after excluding an approximate medial temporal region. The 3-19 Hz residual peak-frequency gradient met the pre-registered rule but was small (rho = -0.046, 95% CI [-0.084, -0.008], Holm p = 0.015), about 3.5 times smaller than previously reported; it was not significant in catFR1 and was near zero with location controls or medial temporal exclusion. In the same 51 earlier patients analyzed with these 60 s spectra, its sign was opposite (rho = +0.076, p = 0.054). The pooled anterior median peak was not lower than the posterior median. These results support replication of the alpha-to-theta gradient but do not show a robust within-patient peak-frequency gradient under the 0.5 Hz method. The aperiodic exponent decreased toward anterior sites (rho = -0.088). Limits include task-start rather than resting segments, the same RAM epilepsy population and sites, an approximate medial temporal mask, one fixed peak rule, bipolar pair orientation and spacing, and no correction for within-subject spatial autocorrelation.

stereo-EEG · spectral gradient · alpha-theta · peak frequency · memory task · replication · MNI coordinates