Cortical minicolumn
A cortical minicolumn (also called cortical microcolumn[1]) is a vertical column through the cortical layers of the brain. Neurons within the microcolumn "receive common inputs, have common outputs, are interconnected, and may well constitute a fundamental computational unit of the cerebral cortex".[2][3] Minicolumns comprise perhaps 80–120 neurons, except in the primate primary visual cortex (V1), where there are typically more than twice the number. There are about 2×108 minicolumns in humans.[4] From calculations, the diameter of a minicolumn is about 28–40 μm.[2] Minicolumns grow from progenitor cells within the embryo and contain neurons within multiple layers (2–6) of the cortex.[5]
Many sources support the existence of minicolumns, especially Mountcastle,[2] with strong evidence reviewed by Buxhoeveden and Casanova[6] who conclude "... the minicolumn must be considered a strong model for cortical organization" and "[the minicolumn is] the most basic and consistent template by which the neocortex organizes its neurones, pathways, and intrinsic circuits".
Cells in 50 μm minicolumn all have the same receptive field; adjacent minicolumns may have different fields.[7]
Number of neurons
[edit]Estimates of number of neurons in a minicolumn range from 80–100 neurons.[6][2][8]
Jones[7] describes a variety of observations that may be interpreted as mini- or micro-columns and gives example numbers from 11 to 142 neurons per minicolumn.
Number of minicolumns
[edit]Estimates of the number of neurons in cortex or in neocortex are on the order of 2×1010.[9][10] Most[11] (perhaps 90%[citation needed]) of cortical neurons are neocortical neurons.
Johansson and Lansner[4] use an estimate of 2×1010 neurons in the neocortex and an estimate of 100 neurons per minicolumn, yielding an estimate of 2×108 minicolumns.
Sporns et al. give an estimate of 2×107 – 2×108 minicolumns.[12]
Size of minicolumns
[edit]The minicolumn measures of the order of 40–50 μm in transverse diameter;[2][6] 35–60 μm;[citation needed] 50 μm with 80 μm spacing,[citation needed] or 30 μm with 50 μm.[citation needed] Larger sizes may not be of human minicolumns, for example macaque monkey V1 minicolumns are 31 μm diameter, with 142 pyramidal cells[citation needed] — 1270 columns per mm2. Similarly, the cat V1 has much bigger minicolumns, ~56 μm.[citation needed]
The size can also be calculated from area considerations. If cortex (both hemispheres) is 1.27×1011 μm2 then if there are 2×108 minicolumns in the neocortex then each is 635 μm2, giving a diameter of 28 μm (if the cortex area were doubled to the commonly quoted value, this would rise to 40 μm). Johansson and Lansner[4] do a similar calculation and arrive at 36 μm (p51, last para).
Downwards projecting axons in minicolumns are ≈10 μm in diameter, periodicity and density similar to those within the cortex, but not necessarily coincident.[citation needed]
See also
[edit]References
[edit]- ^ Cruz, Luis; Buldyrev, Sergey; Peng, Shouyong; Roe, Daniel; Urban, Brigita; Stanley, HE; Rosene, Douglas (February 2005). "A statistically based density map method for identification and quantification of regional differences in microcolumnarity in the monkey brain". Journal of Neuroscience Methods. 141 (3): 321–332. doi:10.1016/j.jneumeth.2004.09.005. PMID 15661314. S2CID 6316809 – via Elsevier Science Direct.
- ^ a b c d e Mountcastle, Vernon (July 1957). "Modality and topographic properties of single neurons of cat's somatic sensory cortex". Journal of Neurophysiology. 20 (4): 408–34. doi:10.1152/jn.1957.20.4.408. PMID 13439410.
- ^ Bennett, Max (July 2020). "An Attempt at a Unified Theory of the Neocortical Microcircuit in Sensory Cortex". Frontiers in Neural Circuits. 14: 40. doi:10.3389/fncir.2020.00040. PMC 7416357. PMID 32848632.
- ^ a b c Johansson, Christopher; Lansner, Anders (2007). "Towards cortex sized artificial neural systems". Neural Networks. 20 (1): 48–61. doi:10.1016/j.neunet.2006.05.029. PMID 16860539.
- ^ Jeff Hawkins, Sandra Blakeslee On Intelligence p. 94
- ^ a b c Buxhoeveden, Daniel P.; Casanova, Manuel F. (May 2002). "The minicolumn hypothesis in neuroscience". Brain. 125 (Pt 5): 935–951. doi:10.1093/brain/awf110. ISSN 0006-8950. PMID 11960884.
- ^ a b Jones, Edward G. (2000-05-09). "Microcolumns in the cerebral cortex". Proceedings of the National Academy of Sciences. 97 (10): 5019–5021. Bibcode:2000PNAS...97.5019J. doi:10.1073/pnas.97.10.5019. ISSN 0027-8424. PMC 33979. PMID 10805761.
- ^ Sporns O, Tononi G, Kötter R. The human connectome: A structural description of the human brain. PLoS Comput. Biol. 2005 Sep1(4):e42.
- ^ Pakkenberg B., Gundersen H. J. G. (1997). "Neocortical Neuron Number in Humans: Effect of Sex and Age". The Journal of Comparative Neurology. 384 (2): 312–320. doi:10.1002/(sici)1096-9861(19970728)384:2<312::aid-cne10>3.3.co;2-g. PMID 9215725.
- ^ Azevedo, Frederico A.C.; Carvalho, Ludmila R.B.; Grinberg, Lea T.; Farfel, José Marcelo; Ferretti, Renata E.L.; Leite, Renata E.P.; Filho, Wilson Jacob; Lent, Roberto; Herculano-Houzel, Suzana (2009). "Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain" (PDF). J. Comp. Neurol. 513 (5): 532–541. doi:10.1002/cne.21974. PMID 19226510. S2CID 5200449.
- ^ Claudia Krebs MD PhD, Joanne Weinberg PhD, Elizabeth Akesson MSc. Lippincott’s Illustrated Reviews: Neuroscience, accessed Nov 10 2013. Chapter 13, II.A, "Histological organization of the cortex"
- ^ Sporns O, Tononi G, Kötter R. The human connectome: A structural description of the human brain. PLoS Comput. Biol. 2005 Sep1(4):e42
External links
[edit]- "W. H. Calvin's "Cortical Columns, Modules, and Hebbian Cell Assemblies" (MIT Press 1995)". williamcalvin.com. Retrieved 2017-12-31.