A novel functional optical mapping procedure for brain is proposed, which is in a periodical mode and the period is much shorter than the duration of the homodynamic course. Under continuous-periodic stimulation, the neural response of cortical functional region enters a stable state. The mapping signals vibrate at the stimulation frequency round some level in state space, which can be detected by the spectral analyzing techniques, and the task related brain region can be determined by synthesizing the altitude and phase distribution of the spectrum. Hind-paw (HP) area of SD mouse with sciatic nerve stimulation is used as the neural model in the experiment, with red light with 605±10 nm wavelength for illumination. The vascular overspill phenomenon is weakened greatly, resulting in a reduction of pseudo-maps. The phase distribution indicates that response of contralateral HP area is temporally prior to that of ipsilateral HP area. The arterial-venous transit and local blood circulation are also discussed. It is found that when relatively high frequency stimulation is applied, the vessel net will resonate with the stimuli. The procedure presents more spatio-temporal information of cortical neural activation than traditional ones, and proves another valuable functional mapping technqiue.