ALFF/fALFF z-maps

Amplitude of Low-Frequency Fluctuation (ALFF) and fractional ALFF (fALFF) maps represent the intensity of spontaneous brain activity during rest. ALFF maps quantify the total power of low-frequency (0.01–0.08 Hz) BOLD signal oscillations at each voxel, reflecting the amplitude of regional spontaneous neural activity. fALFF maps normalize ALFF by dividing it by the total power across the entire frequency range, thereby reducing non-neuronal noise and improving specificity to neural signals. Together, ALFF and fALFF maps provide voxel-wise measures of intrinsic brain activity, highlighting regions with altered amplitude dynamics in patient versus control groups.