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. Author manuscript; available in PMC: 2010 Mar 15.
Published in final edited form as: J Neurosci Methods. 2008 Nov 7;177(2):448–451. doi: 10.1016/j.jneumeth.2008.10.034

Figure 3.

Figure 3

Analysis of coefficients of correlation (R), calculated between the two distributions of pixel brightness values for the stained and unstained eyelids. A. Raw coefficient of correlation values calculated from a 230-second segment of data. Two thresholds were defined by the user (dashed lines) to determine ranges of R-values that corresponded to open or closed eye lids (grey). B. Translation of R-values into state values (blue curve), i.e., 1 (eyes open), 0, (intermediate) or −1 (eyes closed). C. Smoothing of the series of state values (see Methods) to exclude episodes of transient eye closure or opening.