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[4] biomarkers for many neurological conditions including schizophrenia, and ADHD.[2]

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. 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. Wallis, I; Ellis, L; Suh, K; Pfenninger, K. H. (1985). "Immunolocalization of a neuronal growth-dependent membrane glycoprotein". The Journal of Cell Biology. 101 (5 Pt 1): 1990–8. doi:10.1083/jcb.101.5.1990. PMC 2113966. PMID 3902859.
  4. Tachibana, M; Kaneko, A (1988). "Retinal bipolar cells receive negative feedback input from GABAergic amacrine cells". Visual Neuroscience. 1 (3): 297–305. doi:10.1017/S0952523800001954. PMID 2856476.


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