The '''normalization model'''<ref name="pmid22108672 ">{{Cite pmidjournal | last1 = Carandini | first1 = M. | last2 = Heeger | first2 = D. J. | doi = 10.1038/nrn3136 | title = Normalization as a canonical neural computation | journal = Nature Reviews Neuroscience | volume = 13 | issue = 1 | pages = 51–62 | year = 2011 | pmid = 22108672 | pmc =3273486 }}</ref> is an influential model of responses of [[neurons]] in [[primary visual cortex]]. [[David Heeger]] developed the model in the early 1990s,<ref name="pmid1504027 ">{{Cite pmidjournal |1504027 doi = 10.1017/S0952523800009640 | last1 = Heeger | first1 = D. J. | title = Normalization of cell responses in cat striate cortex | journal = Visual neuroscience | volume = 9 | issue = 2 | pages = 181–197 | year = 1992 | pmid = 1504027}}</ref> and later refined it together with [[Matteo Carandini]] and [[J. Anthony Movshon]].<ref name="pmid9334433 ">{{Cite pmidjournal |9334433 last1 = Carandini | first1 = M | last2 = Heeger | first2 = DJ | last3 = Movshon | first3 = JA | title = Linearity and normalization in simple cells of the macaque primary visual cortex | journal = Journal of Neuroscience | volume = 17 | issue = 21 | pages = 8621–44 | year = 1997 | pmid = 9334433}}</ref> The model involves a divisive stage. In the numerator is the output of the classical [[receptive field]]. In the denominator, a constant plus a measure of local stimulus [[Contrast (vision)|contrast]]. Although the normalization model was initially developed to explain responses in the primary visual cortex, normalization is now thought to operate throughout the visual system, and in many other sensory modalities and brain regions, including the representation of odors, the modulatory effects of visual attention, the encoding of value, and the integration of multisensory information. Its presence in such a diversity of neural systems in multiple species, from invertebrates to mammals, suggests that normalization serves as a canonical neural computation.
