Rheoencephalography (REG) is impedance plethysmography applied to the head, and provides an indirect measurement of the pulsatility of the cerebral blood volume. To extend REG as a clinical and research tool, it is necessary to evaluate the sensitivity of REG measurement to local brain conductivity changes. By means of the analytical solution of a four-sphere geometrical model of the head, maps of impedance sensitivity were assessed for different electrode arrangements. Results showed a selective distribution of sensitivities, with a preference for cortical areas under electrodes. This suggests a potential for application of REG to regional evaluation of cortical cerebral perfusion.