The effects of stimulus rates on high frequency oscillations of median nerve somatosensory-evoked potentials – direct recording study from the human cerebral cortex

Objectives: To study the effects of different stimulus rates on high-frequency oscillations (HFOs) of somatosensory-evoked potentials (SEPs), we recorded median nerve SEPs directly from the human cerebral cortex. Methods: SEPs were recorded from subdural electrodes in 5 patients with intractable epilepsy, under the conditions of low (3.3 Hz) and high (12.3 Hz) stimulus rates. Results: Increased stimulus rates to the median nerve from 3.3 to 12.3 Hz showed a pronounced amplitude reduction of HFOs when compared with the primary N20–P20, area 3b, and P25, area 1, responses. Conclusions: HFOs were more sensitive to a high stimulus rate than the primary cortical responses, suggesting that the post-synaptic intracortical activities may greatly contribute to the HFO generation