Fig. 3. Group-averaged transfer function analysis between mean blood pressure (MBP) and cerebral blood flow (CBF) velocity with placebo and two doses of dexmedetomidine (DEX).  Thick lines = averaged estimates;  thin lines = SEMs. Coherence = coherence function; Gain = transfer-function gain between MBP and CBF velocity; HF = high-frequency range (0.20–0.30 Hz); LF = low-frequency range (0.07–0.20 Hz); Phase = phase relation between MBP and CBF velocity; VLF = very-low-frequency range (0.02–0.07 Hz).