Amplitude of low frequency fluctuations

Amplitude of Low Frequency Fluctuations (ALFF) and fractional Amplitude of Low Frequency Fluctuations (f/ALFF) are neuroimaging methods used to measure spontaneous fluctuations in BOLD-fMRI signal intensity for a given region in the resting brain. Electrophysiological studies suggest that low-frequency oscillations arise from spontaneous neuronal activity. Though ALFFs have been researched extensively in fMRI based theoretical models of brain function, their actual significance is still unknown.^[1]

Default mode network

Whole-brain ALFF shows greater signal in posterior cingulate, precuneus, and medial prefrontal areas of the default mode network,^[2] but also in non-cortical areas near the ventricles, cisterns and large blood vessels. f/ALFF reduces the sensitivity of ALFF to physiological noise by taking the ratio of each frequency (0.01-0.08 Hz) to the total frequency range (0-0.25 Hz).^[3] Both measures have been investigated as part of reliable biomarkers^{[citation needed]} for many neurological conditions including schizophrenia,^{[citation needed]} anorexia nervosa,^[4] and ADHD^{[citation needed]}.

References

1. Cordes, D; Haughton, VM; Arfanakis, K; Carew, JD; Turski, PA; Moritz, CH; Quigley, MA; Meyerand, ME (August 2001). "Frequencies contributing to functional connectivity in the cerebral cortex in "resting-state" data". AJNR. American Journal of Neuroradiology. 22 (7): 1326–33. PMC 7975218. PMID 11498421.
2. Zang, Y. F.; He, Y; Zhu, C. Z.; Cao, Q. J.; Sui, M. Q.; Liang, M; Tian, L. X.; Jiang, T. Z.; Wang, Y. F. (2007). "Altered baseline brain activity in children with ADHD revealed by resting-state functional MRI". Brain and Development. 29 (2): 83–91. doi:10.1016/j.braindev.2006.07.002. PMID 16919409. S2CID 53161518.
3. Zou QH, Zhu CZ, Yang Y, Zuo XN, Long XY, Cao QJ; et al. (2008). "An improved approach to detection of amplitude of low-frequency fluctuation (ALFF) for resting-state fMRI: fractional ALFF". J Neurosci Methods. 172 (1): 137–41. doi:10.1016/j.jneumeth.2008.04.012. PMC 3902859. PMID 18501969.{{cite journal}}: CS1 maint: multiple names: authors list (link)
4. Seidel, Maria; Borchardt, Viola; Geisler, Daniel; King, Joseph A.; Boehm, Ilka; Pauligk, Sophie; Bernardoni, Fabio; Biemann, Ronald; Roessner, Veit; Walter, Martin; Ehrlich, Stefan (2019-11-01). "Abnormal Spontaneous Regional Brain Activity in Young Patients With Anorexia Nervosa". Journal of the American Academy of Child & Adolescent Psychiatry. 58 (11): 1104–1114. doi:10.1016/j.jaac.2019.01.011. ISSN 0890-8567. PMID 30768380. S2CID 73438473.