NIMG-100. THE MEDIAN NERVE STIMULATION INDUCES LONG LATENCY GAMMA MODULATIONS IN THE PRIMARY SOMATOSENSORY CORTEX, WHICH DIFFERENTIATES THE CONSCIOUS STATE

Abstract OBJECTIVE While the intraoperative assessment of short-latency somatosensory evoked potentials (SSEPs) phase reversal in electrocorticogram (ECoG) is routinely used to locate central sulcus (CS), its spatial-spectral patterns primary sensorimotor cortex and relation consciousness not well characterized. Our goal was evaluate functional utility using median nerve stimulation-induced ECoG sub-band modulations pre-and post-CS differentiate between anesthetized awake states. Method: SSEPs were recorded from with during routine cortical mapping 8 patients We conducted a time-frequency analysis on SSEP trace each state extract spectral up 900Hz contrasted their intensity M1 S1 discern RESULTS observed late gamma activity ranging 60-250Hz, starting approximately 50ms after stimulation onset extending 250ms. The suppressed both (p< 0.01) (p=0.0369). Whiles state, power increased significantly respect baseline (p=0.0180) 0.01). difference highly significant for CONCLUSION results show that besides CS delineation, long latency can serve as an additional biomarker monitor level neurosurgical practice.