A cortical minicolumn 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".
Minicolumns comprise perhaps 80–120 neurons, except in the
primate primary visual cortex
The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...
(V1), where there are typically more than twice the number. There are about 2×10
8 minicolumns in humans.
From calculations, the diameter of a minicolumn is about 28–40 μm.
Minicolumns grow from
progenitor cell
A progenitor cell is a biological cell that can differentiate into a specific cell type. Stem cells and progenitor cells have this ability in common. However, stem cells are less specified than progenitor cells. Progenitor cells can only differ ...
s within the embryo and contain neurons within multiple layers (2–6) of the cortex.
![Bennet2020Figure2CorticalColumn](https://upload.wikimedia.org/wikipedia/commons/9/94/Bennet2020Figure2CorticalColumn.jpg)
Many sources support the existence of minicolumns, especially
Mountcastle,
with strong evidence reviewed by Buxhoeveden and Casanova
who conclude "... the minicolumn must be considered a strong model for cortical organization" and "
he minicolumn is/nowiki> the most basic and consistent template by which the neocortex organizes its neurones, pathways, and intrinsic circuits".
Cortical minicolumns can also be called cortical microcolumns. Cells in 50 μm minicolumn all have the same receptive field
The receptive field, or sensory space, is a delimited medium where some physiological stimuli can evoke a sensory neuronal response in specific organisms.
Complexity of the receptive field ranges from the unidimensional chemical structure of o ...
; adjacent minicolumns may have different fields.
Number of neurons
Estimates of number of neurons in a minicolumn range from 80–100 neurons.[Sporns O, Tononi G, Kötter R]
The human connectome: A structural description of the human brain
PLoS Comput. Biol. 2005 Sep1(4):e42.
Jones 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
Estimates of the number of neurons in cortex or in neocortex are on the order of 2×1010. Most[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" (perhaps 90%) of cortical neurons are neocortical neurons.
Johansson and Lansner 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.[Sporns O, Tononi G, Kötter R]
The human connectome: A structural description of the human brain
PLoS Comput. Biol. 2005 Sep1(4):e42
Size of minicolumns
The minicolumn measures of the order of 40–50 μm in transverse diameter; 35–60 μm; 50 μm with 80 μm spacing, or 30 μm with 50 μm. Larger sizes may not be of human minicolumns, for example macaque monkey V1 minicolumns are 31 μm diameter, with 142 pyramidal cells — 1270 columns per mm2. Similarly, the cat V1 has much bigger minicolumns, ~56 μm.
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 do a similar calculation and arrive at 36 μm (p51, last para).
Downwards projecting axon
An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...
s in minicolumns are ≈10 μm in diameter, periodicity and density similar to those within the cortex, but not necessarily coincident.
See also
*Cortical column
A cortical column is a group of neurons forming a cylindrical structure through the cerebral cortex of the brain perpendicular to the cortical surface. The structure was first identified by Mountcastle in 1957. He later identified cortical minicolu ...
References
External links
*
{{DEFAULTSORT:Cortical Minicolumn
Cerebrum