Word-evoked HFA latency increased across posterior-to-anterior sites, but the preregistered test was not significant

We tested whether visual word-evoked 70–150 Hz high-frequency activity (HFA) began later at more anterior ventral visual and medial temporal lobe (MTL) sites. Using bipolar SEEG from 59 participants in OpenNeuro ds004789 (RAM FR1, session 0; first 72 eligible words; epochs timed by events.tsv sample/fs), we found median half-maximum latencies of 82 ms in occipital, 132 ms in ventral temporal, and 224 ms in MTL pairs. The preregistered subject-level test included five participants with at least four responsive pathway pairs; all five had positive latency–anterior/posterior correlations, but the two-sided sign-flip test was not significant (mean Fisher z = 0.83; p = 0.063). With five participants, the smallest possible two-sided p was 0.0625. Responsive pairs were uncommon in the MTL (6 of 437) and absent in the temporal pole (0 of 42). Secondary tests with more participants were significant without multiple-comparison correction; peak-time latency gave weaker results. Occipital HFA began about 80 ms after the sample/fs word time, consistent with the stated timing rule. The results agree with a posterior-to-anterior latency increase, but the primary test did not establish it. The analysis stopped after 59 of 133 listed participants at a fixed 20-minute fetch limit, and few participants had responsive sites at both posterior and anterior locations.

SEEG · high-frequency activity · word encoding · latency · ventral visual stream · medial temporal lobe · preregistered analysis · OpenNeuro ds004789