Laser-Doppler imaging of activation-flow coupling in the somatosensory cortex: normalization of signal when the...

This study describes two approaches used to normalize the laser-Doppler flowmetry (LDF) signal, corresponding to the regional cerebral blood flow (rCBF) response after electrical hind-paw stimulation. The first approach divides the LDF signal to the baseline and subsequently integrates the response curve from the rise point to the termination point (defined formally as "normalized rCBF response", and the second subtracts the baseline from the LDF signal and subsequently integrates the response curve from the rise point to the termination point (defined as "absolute rCBF response"). Both parameters are given in arbitrary units. A comparative analysis of the changes in the "normalized" and "absolute" LDrCBF response is presented both for when the baseline does not change significantly, and for when the baseline changes significantly under the influence of different factors. In summary, when the baseline changes significantly it is preferable to normalize the LDrCBF response towards the baseline by subtraction, not by division.