Fig. 10.

Estimating cerebral and scalp contributions to measured data. Measured signals (solid lines) were fitted as a sum of non-negative weighted contributions from the two modelled compartments, minimising total error over both ${\mathrm{HbO}}_2$ and HHb. Dashed lines show the fitted signals, and the values in the top left corner of each plot show the relative contributions of the scalp (S) and cerebral (C) compartments to the fits. A (Subject S8, as in Fig. 8.) At short distance, the best fit contains no cerebral contribution at all, while at the longer distance the scalp component is less than the cerebral. B (Subject S2, as in Fig. 9.) As would be expected, the short distance fit includes a larger scalp contribution than the long distance. It is notable that some (activated) cerebral contribution is included at both distances, despite the lack of a characteristic functional activation response in the HHb.