Figure 4From: Human cortical perfusion and the arterial pulse: a near-infrared spectroscopy studyCross correlation function of the perfusion signal with reference to the arterial pulse (green trace) superimposed on a background (yellow) of 16 surrogate cross correlation functions computed from phase-randomization. The upper and lower red dash lines demarcate the boundaries of ± 3 standard deviations of the surrogates.Back to article page