Mini-columns
Mini-columns
- Description
Mini-columns are thought to be a fundamental element of cortical information processing. 1They have been evolutionarily conserved in all mammalian species and are generally adapted according to specific functional requirements. At the core and periphery of the minicolumn are combinations of GABAergic interneurons which modulate pyramidal cell inputs and outputs. 2
Changes in mini-columns may explain deficits in complex information processing, such as that which is employed in executive functioning.1 In particular, smaller minicolumns increases the distance between neighboring neurons and thus can reduce functional connectivity.2
As expected, there is a decrease in size of the gyral window, which is a plane through which afferent and efferent fibers connect the cortex to its underlying white matter. This makes sense because the increase in minicolumns increases the cortical surface area.5
With the change in minicolumns, long-range connectivity and integration of different brain regions decrease because of the limitations on the gyral window. Shorter connections between the cortical tracts are reinforced, and thus there is hyperconnectivity within the circuit. This leads to poorer coordination for tasks which require integration such as language or socialization, but increased abilities on tasks which depend on individual cortical areas. This contrasts to minicolumns seen in Dyslexia.5
Mini-columns and ASD
Minicolumns in those with autism are smaller and more numerous.
Imaging data suggest that autism is the result of a developmental lesion that affects brain growth. Other studies3,4 have provided evidence that minicolumn abnormalities are not an effect of mental retardation. it is hypothesized that the increase in minicolumns is a result of increased brain growth relative to the body (encephalization). Smaller minicolumns might reflect increased processing complexity.
Concerns
Minicolumn measurements require a special expertise and as a result, few studies have been done. In addition, sample sizes have been small.
Citations
1. Geschwind DH. Advances in autism. Annu Rev Med. 2009;60:367-80. PMID 19630577
2. Casanova MF et. al. Minicolumnar abnormalities in autism.Acta Neuropathol. 2006 Sep;112(3):287-303 PMID 16819561
3. Buxhoeveden D et. al. Quantitative comparison of radial cell columns in children with Down's syndrome and controls.J Intellect Disabil Res. 2002 Jan;46(Pt 1):76-81. PMID 11851858
4. Buxhoeveden D et. al. Accelerated maturation in brains of patients with Down syndrome. J Intellect Disabil Res. 2004 Oct;48(Pt 7):704-5. PMID 15357692
5. Williams EL et. al. Autism and dyslexia: a spectrum of cognitive styles as defined by minicolumnar morphometry.Med Hypotheses. 2010 Jan;74(1):59-62. PMID 19713047
