A cortical minicolumn (also called cortical microcolumn<ref>Template:Cite journal</ref>) 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".<ref name="Mountcastle1957">Template:Cite journal</ref><ref>Template:Cite journal</ref> 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.<ref name=":0">Template:Cite journal</ref> From calculations, the diameter of a minicolumn is about 28–40 μm.<ref name="Mountcastle1957" /> Minicolumns grow from progenitor cells within the embryo and contain neurons within multiple layers (2–6) of the cortex.<ref>Jeff Hawkins, Sandra Blakeslee On Intelligence p. 94</ref>
Many sources support the existence of minicolumns, especially Mountcastle,<ref name="Mountcastle1957" /> with strong evidence reviewed by Buxhoeveden and Casanova<ref name=":2">Template:Cite journal</ref> 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.<ref name="Jones2000"/>
Number of neuronsEdit
Estimates of number of neurons in a minicolumn range from 80–100 neurons.<ref name=":2" /><ref name="Mountcastle1957" /><ref>Sporns O, Tononi G, Kötter R. The human connectome: A structural description of the human brain. PLoS Comput. Biol. 2005 Sep1(4):e42.</ref>
Jones<ref name="Jones2000">Template:Cite journal</ref> 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 minicolumnsEdit
Estimates of the number of neurons in cortex or in neocortex are on the order of 2×1010.<ref name="Neocortical Neuron Number in Humans: Effect of Sex and Age">Template:Cite journal</ref><ref name="Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain">Template:Cite journal</ref> Most<ref name="Lippincott’s Illustrated Reviews: Neuroscience">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"</ref> (perhaps 90%Template:Citation needed) of cortical neurons are neocortical neurons.
Johansson and Lansner<ref name=":0" /> 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.<ref name="The human connectome: A structural description of the human brain">Sporns O, Tononi G, Kötter R. The human connectome: A structural description of the human brain. PLoS Comput. Biol. 2005 Sep1(4):e42</ref>
Size of minicolumnsEdit
The minicolumn measures of the order of 40–50 μm in transverse diameter;<ref name="Mountcastle1957" /><ref name=":2" /> 35–60 μm;Template:CN 50 μm with 80 μm spacing,Template:CN or 30 μm with 50 μm.Template:CN Larger sizes may not be of human minicolumns, for example macaque monkey V1 minicolumns are 31 μm diameter, with 142 pyramidal cellsTemplate:CN — 1270 columns per mm2. Similarly, the cat V1 has much bigger minicolumns, ~56 μm.Template:CN
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<ref name=":0" /> 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.Template:CN
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