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Cartoon of a locust interneuron that integrates information about wind in order to control wing motor neurons during flight[1]
LocationNervous system
NeuroLex IDbirnlex_2534
Anatomical terms of neuroanatomy

Interneurons (also called internuncial neurons, relay neurons, association neurons, connector neurons, intermediate neurons or local circuit neurons) are neurons that connect to brain regions, i.e. not direct motor neurons or sensory neurons. Interneurons are the central nodes of neural circuits, enabling communication between sensory or motor neurons and the central nervous system (CNS).[2] They play vital roles in reflexes, neuronal oscillations,[3] and neurogenesis in the adult mammalian brain.[citation needed]

Interneurons can be further broken down into two groups: local interneurons and relay interneurons.[4][need quotation to verify] Local interneurons have short axons and form circuits with nearby neurons to analyze small pieces of information.[5] Relay interneurons have long axons and connect circuits of neurons in one region of the brain with those in other regions.[5] However, interneurons are generally considered to operate mainly within local brain areas.[6] The interaction between interneurons allow the brain to perform complex functions such as learning, and decision-making.


Approximately 20–30% of the neurons in the neocortex are interneurons, while the remaining neurons are pyramidal neurons.[7] Investigations into the molecular diversity of neurons is impeded by the inability to isolate cell populations born at different times for gene expression analysis. An effective means of identifying coetaneous interneurons is neuronal birthdating.[8] This can be achieved using nucleoside analogs such as EdU.[9][8]

In 2008, a nomenclature for the features of GABAergic cortical interneurons was proposed, called Petilla terminology.[10]

Spinal cord[edit]


  • Parvalbumin-expressing interneurons
  • CCK-expressing interneurons
  • VIP-expressing interneurons
  • SOM-expressing interneurons[11]




Interneurons in the CNS are primarily inhibitory, and use the neurotransmitter GABA or glycine. However, excitatory interneurons using glutamate in the CNS also exist, as do interneurons releasing neuromodulators like acetylcholine.

In addition to these general functions, interneurons in the insect CNS play a number of specific roles in different parts of the nervous system, and also are either excitatory or inhibitory. For example, in the olfactory system, interneurons are responsible for integrating information from odorant receptors and sending signals to the mushroom bodies, which are involved in learning and memory.[17][18] In the visual system, interneurons are responsible for processing motion information and sending signals to the optic lobes, which are involved in visual navigation.[19][20]

Interneurons are also important for coordinating complex behaviors, such as flight and locomotion. For example, interneurons in the thoracic ganglia are responsible for coordinating the activity of the leg muscles during walking[21] and flying.[22]

Interneurons main function is to provide a neural circuit, conducting flow of signals or information between a sensory neuron and or motor neuron.[23]

See also[edit]


  1. ^ Pearson, K. G. and Wolf, H. Connections of hindwing tegulae with flight neurones in the locust, Locusta migratoria. J. Exp. Biol. 135: 381-409, 1988
  2. ^ "Types of neurons - Queensland Brain Institute - University of Queensland". 9 November 2017.
  3. ^ Whittington, M.A; Traub, R.D; Kopell, N; Ermentrout, B; Buhl, E.H (2000). "Inhibition-based rhythms: Experimental and mathematical observations on network dynamics". International Journal of Psychophysiology. 38 (3): 315–36. CiteSeerX doi:10.1016/S0167-8760(00)00173-2. PMID 11102670.
  4. ^ Carlson, Neil R. (2013). Physiology of Behavior (11th ed.). Pearson Higher Education. p. 28. ISBN 978-0-205-23939-9.
  5. ^ a b Kandel, Eric; Schwartz, James; Jessell, Thomas, eds. (2000). Principles of Neural Science (4th ed.). New York City, New York: McGraw Hill Companies. p. 25. ISBN 978-0-8385-7701-1.
  6. ^ Kepecs, Adam; Fishell, Gordon (2014). "Interneuron Cell Types: Fit to form and formed to fit". Nature. 505 (7483). Nature , 2014 HHS Public Access pp 10, 28: 318–326. doi:10.1038/nature12983. PMC 4349583. PMID 24429630.
  7. ^ Markram, Henry; et al. (2004). "Interneurons of the neocortical inhibitory system". Nature Reviews Neuroscience. 5 (10): 793–807. doi:10.1038/nrn1519. PMID 15378039. S2CID 382334.
  8. ^ a b Ng, Hui Xuan; Lee, Ean Phing; Cavanagh, Brenton L.; Britto, Joanne M.; Tan, Seong-Seng (2017). "A method for isolating cortical interneurons sharing the same birthdays for gene expression studies". Experimental Neurology. 295: 36–45. doi:10.1016/j.expneurol.2017.05.006. PMID 28511841. S2CID 3377296.
  9. ^ Endaya, Berwini; Cavanagh, Brenton; Alowaidi, Faisal; Walker, Tom; Pennington, Nicholas de; Ng, Jin-Ming A.; Lam, Paula Y.P.; Mackay-Sim, Alan; Neuzil, Jiri (2016). "Isolating dividing neural and brain tumour cells for gene expression profiling". Journal of Neuroscience Methods. 257: 121–133. doi:10.1016/j.jneumeth.2015.09.020. PMID 26432933. S2CID 44969376.
  10. ^ Ascoli, Giorgio A.; Alonso-Nanclares, Lidia; Anderson, Stewart A.; Barrionuevo, German; Benavides-Piccione, Ruth; Burkhalter, Andreas; Buzsáki, György; Cauli, Bruno; Defelipe, Javier; Fairén, Alfonso; Feldmeyer, Dirk; Fishell, Gord; Fregnac, Yves; Freund, Tamas F.; Gardner, Daniel; Gardner, Esther P.; Goldberg, Jesse H.; Helmstaedter, Moritz; Hestrin, Shaul; Karube, Fuyuki; Kisvárday, Zoltán F.; Lambolez, Bertrand; Lewis, David A.; Marin, Oscar; Markram, Henry; Muñoz, Alberto; Packer, Adam; Petersen, Carl C. H.; Rockland, Kathleen S.; et al. (2008). "Petilla terminology: Nomenclature of features of GABAergic interneurons of the cerebral cortex". Nature Reviews Neuroscience. 9 (7): 557–68. doi:10.1038/nrn2402. PMC 2868386. PMID 18568015.
  11. ^ Muñoz, W; Tremblay, R; Levenstein, D; Rudy, B (3 March 2017). "Layer-specific modulation of neocortical dendritic inhibition during active wakefulness". Science. 355 (6328): 954–959. Bibcode:2017Sci...355..954M. doi:10.1126/science.aag2599. PMID 28254942.
  12. ^ Tepper, James M.; Koós, Tibor (1999). "Inhibitory control of neostriatal projection neurons by GABAergic interneurons". Nature Neuroscience. 2 (5): 467–72. doi:10.1038/8138. PMID 10321252. S2CID 16088859.
  13. ^ Zhou, Fu-Ming; Wilson, Charles J.; Dani, John A. (2002). "Cholinergic interneuron characteristics and nicotinic properties in the striatum". Journal of Neurobiology. 53 (4): 590–605. doi:10.1002/neu.10150. PMID 12436423.
  14. ^ English, Daniel F; Ibanez-Sandoval, Osvaldo; Stark, Eran; Tecuapetla, Fatuel; Buzsáki, György; Deisseroth, Karl; Tepper, James M; Koos, Tibor (2011). "GABAergic circuits mediate the reinforcement-related signals of striatal cholinergic interneurons". Nature Neuroscience. 15 (1): 123–30. doi:10.1038/nn.2984. PMC 3245803. PMID 22158514.
  15. ^ Ibanez-Sandoval, O.; Tecuapetla, F.; Unal, B.; Shah, F.; Koos, T.; Tepper, J. M. (2010). "Electrophysiological and Morphological Characteristics and Synaptic Connectivity of Tyrosine Hydroxylase-Expressing Neurons in Adult Mouse Striatum". Journal of Neuroscience. 30 (20): 6999–7016. doi:10.1523/JNEUROSCI.5996-09.2010. PMC 4447206. PMID 20484642.
  16. ^ a b Ibáñez-Sandoval, Osvaldo; Koós, Tibor; Tecuapetla, Fatuel; Tepper, James M. (2010). "Heterogeneity and Diversity of Striatal GABAergic Interneurons". Frontiers in Neuroanatomy. 4: 150. doi:10.3389/fnana.2010.00150. PMC 3016690. PMID 21228905.
  17. ^ Liou, Nan-Fu; Lin, Shih-Han; Chen, Ying-Jun; Tsai, Kuo-Ting; Yang, Chi-Jen; Lin, Tzi-Yang; Wu, Ting-Han; Lin, Hsin-Ju; Chen, Yuh-Tarng; Gohl, Daryl M.; Silies, Marion; Chou, Ya-Hui (2018-06-08). "Diverse populations of local interneurons integrate into the Drosophila adult olfactory circuit". Nature Communications. 9 (1): 2232. Bibcode:2018NatCo...9.2232L. doi:10.1038/s41467-018-04675-x. ISSN 2041-1723. PMC 5993751. PMID 29884811.
  18. ^ Zheng, Zhihao; Li, Feng; Fisher, Corey; Ali, Iqbal J.; Sharifi, Nadiya; Calle-Schuler, Steven; Hsu, Joseph; Masoodpanah, Najla; Kmecova, Lucia; Kazimiers, Tom; Perlman, Eric; Nichols, Matthew; Li, Peter H.; Jain, Viren; Bock, Davi D. (August 2022). "Structured sampling of olfactory input by the fly mushroom body". Current Biology. 32 (15): 3334–3349.e6. doi:10.1016/j.cub.2022.06.031. ISSN 0960-9822. PMC 9413950. PMID 35797998.
  19. ^ Zhu, Yan (2013-07-29). "The Drosophila visual system: From neural circuits to behavior". Cell Adhesion & Migration. 7 (4): 333–344. doi:10.4161/cam.25521. ISSN 1933-6918. PMC 3739809. PMID 23880926.
  20. ^ Shinomiya, Kazunori; Nern, Aljoscha; Meinertzhagen, Ian A.; Plaza, Stephen M.; Reiser, Michael B. (August 2022). "Neuronal circuits integrating visual motion information in Drosophila melanogaster". Current Biology. 32 (16): 3529–3544.e2. doi:10.1016/j.cub.2022.06.061. ISSN 0960-9822. PMID 35839763.
  21. ^ Bidaye, Salil S.; Laturney, Meghan; Chang, Amy K.; Liu, Yuejiang; Bockemühl, Till; Büschges, Ansgar; Scott, Kristin (November 2020). "Two Brain Pathways Initiate Distinct Forward Walking Programs in Drosophila". Neuron. 108 (3): 469–485.e8. doi:10.1016/j.neuron.2020.07.032. PMC 9435592. PMID 32822613.
  22. ^ King, David G.; Wyman, Robert J. (1980-12-01). "Anatomy of the giant fibre pathway inDrosophila. I. Three thoracic components of the pathway". Journal of Neurocytology. 9 (6): 753–770. doi:10.1007/BF01205017. ISSN 1573-7381. PMID 6782199. S2CID 10530883.
  23. ^ "Types of Neurons". University of Queensland. Queensland Brain Institute. 9 November 2017. Retrieved 26 April 2023.