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 (3.3Hz) and high (12.3Hz) stimulus rates. RESULTS Increased stimulus rates to the median nerve from 3.3 to 12.3Hz 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.

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