# Chemoaffinity hypothesis

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In [neuroscience](/source/Neuroscience), the **chemoaffinity hypothesis** states that [neurons](/source/Neuron) make [connections](/source/Neural_pathway) with their targets based on interactions with specific [molecular markers](/source/Molecular_marker)[1][unreliable source?] and, therefore, that the initial [wiring diagram](/source/Wiring_diagram) of an organism is (indirectly) determined by its [genotype](/source/Genotype). The markers are generated during [cellular differentiation](/source/Cellular_differentiation) and aid not only with [synaptogenesis](/source/Synaptogenesis), but also act as guidance cues for their respective [axon](/source/Axon).[1]

## Sperry's experiments

[Roger Wolcott Sperry](/source/Roger_Wolcott_Sperry) pioneered the inception of the chemoaffinity hypothesis following his 1960s experiments on the [African clawed frog](/source/African_clawed_frog).[2] He would remove the eye of a frog and reinsert it rotated upside-down—the visual nervous system would eventually repair itself,[3] and the frog would exhibit inverted vision. In other words, the initial eye orientation is reversed such that the [dorsal](/source/Dorsal_(anatomy)) part of the eye becomes the [ventral](/source/Ventral) side, and the ventral side becomes the dorsal side; when a food source was put above the frog, the frog would extend its tongue downwards.[4] In follow-up experiments, the eye was detached and rotated 180° like before, but additionally the optic nerve was cut—the results were identical.[citation needed]

Sperry hypothesized that each individual [optic nerve](/source/Optic_nerve) and [tectal neuron](/source/Tectum) used some form of chemical marker to dictate the connectivity during development. Sperry reasoned that when the eye had been rotated, each optic fiber and tectal neuron possessed cytochemical labels that uniquely denoted their type and position, and thus optic fibers utilize these labels to selectively navigate to their matching target cell via a sort-of [chemotaxis](/source/Chemotaxis).[2]

## See also

- [Neural development](/source/Neural_development)

## References

1. ["BIO254:Chemoaffinity"](http://openwetware.org/wiki/BIO254:Chemoaffinity). OpenWetWare. Retrieved 1 September 2011.

1. Ronald L. Meyer (1998). "Roger Sperry and his Chemoaffinity Hypothesis". *Neuropsychologia*. **36** (10): 957–980. [doi:10.1016/S0028-3932(98)00052-9](https://doi.org/10.1016/S0028-3932(98)00052-9). [PMID 9845045](https://pubmed.ncbi.nlm.nih.gov/9845045). [S2CID 5665287](https://api.semanticscholar.org/CorpusID:5665287)

1. Ferry, Gorgina (10 June 1989). ["The nervous system repairs to the network"](https://www.newscientist.com/article/mg12216687.200-the-nervous-system-repairs-to-the-network.html). *New Scientist*. '***(1668). Retrieved 1 September 2011.******(subscription required)***

1. Roger W. Sperry (1943). "Effect of 180 Degree Rotation of the Retinal Field on Visuomotor Coordination". *The Journal of Experimental Zoology*. **92** (3): 263–279. [Bibcode:1943JEZ....92..263S](https://ui.adsabs.harvard.edu/abs/1943JEZ....92..263S). [doi:10.1002/jez.1400920303](https://doi.org/10.1002/jez.1400920303)

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Adapted from the Wikipedia article [Chemoaffinity hypothesis](https://en.wikipedia.org/wiki/Chemoaffinity_hypothesis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Chemoaffinity_hypothesis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.