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. Author manuscript; available in PMC: 2009 Nov 9.
Published in final edited form as: J Sleep Res. 2008 Jun 28;17(3):251–262. doi: 10.1111/j.1365-2869.2008.00652.x

Figure 2.

Figure 2

Schematic illustration of the method used to compute the ‘median’ value of the heart rate variability spectral index representative of each sleep-wake state. LHR, low-to-high frequency power ratio; R, REM; W, wakefulness; S1, S2, S3: sleep Stage 1, 2, 3).