In one SEEG patient, superior temporal high-gamma responses persisted to sentence offset, but the posterior onset gradient was not detected

We tested two pre-registered predictions about high-gamma (HG; 70–150 Hz) responses to sentences in one patient recorded with stereo-electroencephalography (SEEG). The analyzed run contained 126 unique TIMIT sentences from OpenNeuro ds004993 sub-W3, task timit4. We formed 148 bipolar pairs of adjacent contacts on the same shaft; 32 pairs showed a significant positive HG response from 0.05 to 0.5 s after sentence onset. For H1, the baseline-corrected HG integral from onset to sentence offset increased with sentence duration in 29 of 32 responsive pairs (median Spearman rho = 0.147; sign-test p = 2.6 × 10⁻⁶); 14 pairs had positive duration-shuffle p < 0.05. The result persisted in a control that removed narrow bands around VNS harmonics (24 of 31 pairs positive; median rho = 0.160; p = 0.0033). This supports persistence of the response to sentence offset, but does not show that HG encodes sentence content: a response above baseline makes the integral increase with window length by construction. For H2, the pre-registered posterior onset gradient was not supported. In pairs with both contacts labeled temporal (n = 13), right-hemisphere rho was −0.006 (n = 10, p = 1.0) and the pooled permutation test stratified within hemisphere had p = 0.52. Contacts covered a narrow anterior-posterior range, limiting this test. Exploratory results showed onset-dominant responses in the three most posterior-lateral right STG pairs, but one mid-position pair also had this pattern. These data are from one subject and one run and do not generalize to a population.

stereo-electroencephalography · SEEG · high-gamma activity · speech · superior temporal gyrus · sentence duration · vagus nerve stimulator artifact