In seven SEEG patients, longer fixation periods were associated with higher pre-Go beta power, not the predicted decrease

We tested whether longer fixation periods predict lower pre-Go beta power, as expected under temporal-expectation accounts, in a cued two-choice task from OpenNeuro ds004473. Eight patients had random fixation durations F and independent inter-stimulus intervals I (each 0.3–0.7 s). For each bipolar SEEG pair, we regressed log power in the 0.5 s before Go on F and I, trial number, and block type. The primary analysis used movement-responsive pairs in seven patients. Beta power (14–30 Hz) did not decrease with longer F: the estimated change from 0.3 to 0.7 s was +0.31 dB (95% t interval +0.02 to +0.60; six of seven patients positive; exact sign-flip p = 0.031; Holm-adjusted p = 0.063). High gamma (70–110 Hz) did not change (+0.02 dB, interval −0.12 to +0.17, p = 0.72). In a pre-fixation negative-control window, the F effect was near zero. Reaction time showed no clear effect of F or I. A possible explanation for the positive beta estimate is recovery from a fixation-onset beta decrease; this mechanism was not tested. The sample comprised seven patients with responsive pairs, mostly clinical contacts outside motor cortex, and one 0.5 s window. The primary beta result was not significant after correction. EDF records were fetched from unversioned OpenNeuro S3 URLs with hashes preserved; the source report names snapshot 1.0.2, while packaged dataset metadata records version 1.0.1, so the exact EDF release is uncertain.

stereoelectroencephalography · SEEG · beta power · temporal expectation · foreperiod · fixation duration · motor preparation · high gamma · reaction time