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. Author manuscript; available in PMC: 2013 Nov 15.
Published in final edited form as: Neuroimage. 2012 Jul 20;63(3):1571–1584. doi: 10.1016/j.neuroimage.2012.07.015

Fig. 7.

Fig. 7

Phasor representation of the LFOs during various sleep conditions (wake, Stage1, Stage 2, Stage 3, Stage 4, REM). The numerical concentration quantifies the radial coordinate by specifying the amplitude of [HbO]M (the phasor of measured [HbO]) which is taken as the phase reference and thus is always represented by a horizontal phasor. The phasor of measured [Hb] is indicated by [Hb]M. The oxy-hemoglobin phasors associated with blood volume LFOs ([HbO]V) are indicated with V, while those associated with flow velocity ([HbO]F) are indicated with F. The corresponding deoxy-hemoglobin phasors are readily identified in the figure by recalling that [Hb]V = k[HbO]V and [Hb]F = −[HbO]F (see text for details).