A) Plots of absorbance and standard deviation averaged across all experiments (n = 5). All data was normalized prior to being averaged. Plotted absorbances were measured within the ROI which was defined as all pixels within a 1 mm radius of the center of activation (as defined from spatial histogram analysis). Controls in which no stimulus was administered are plotted simultaneously for comparison to test conditions. B) Plot of ΔAbsorbanceevoked which was defined as the change in absorbance measured from frame 1 (prior to stimulus onset) to frame 11 (point of stimulus offset). The plot is fit with a linear function (solid line) described by the equation A = (4 × 10-6)d + 0.0005 where A is absorbance and d is stimulus amplitude (displacement). Coefficient of determination for the linear regression (R2) is shown below.