This paper presents mathematical frameworks, with the purpose to identify the best approach for the assessment of dynamic cerebral autoregulation. The cerebral blood flow velocity (CBFV) was measured by transcranial Doppler (TCD) ultrasonograph and mean arterial blood pressure (MABP) was non-invasively measured using vascular unloading technique, in order to determine the status of autoregulation. The findings show that cerebral autoregulation is a non-stationary and non linear system, thus linear transfer function analysis is not a valid technique for studying the relationship between CBFV and MABP. While wavelet based analyses have shown better performance for the extraction of spontaneous oscillation in the cerebral autoregulation system.