Figure 7: Median SSEPs phase reversal technique: anesthetic induced changes. Panel A shows cortical SSEPs recorded via an 8 contact strip, during anesthesia with nitrous oxide and sevoflurane: the exact location of N19/P22 potentials as well as phase reversal of the recorded dipole are hard to appreciate. Panel B shows recording via the same strip, in the same position, after the anesthetic regimen has been changed to TIVA. Notice a clear phase reversal of recorded SSEPs (line) at the level of the central sulcus, placing contact 4 in the postcentral region and contact 5 in the precentral region.