Fig. 5.
Power spectral density analysis of frontopolar cortex signals during the first removal of soft tissue in surgical patients under general anesthesia. (A) Demonstrations of functional near infrared spectroscopy signal quality (oxygenated hemoglobin concentration changes) and surgical procedures in two example patients: patient 5 (above) and patient 4 (below). (B) Patients without additional nerve block showed significant lower slow-5 fractional power compared with those with nerve block in C2 and C3 (green arrows). Interestingly, increased fractional power of slow-4 band was also noticed in patients without nerve block in C1, C3, and C7. Error bars show the SEM. (C) Bar plots and the P values from two-tailed two-sample t tests of the slow-5 and slow-4 fractional power values. Significant P values after false discovery rate correction are marked with asterisks.