The Minicolumn and Evolution of the Brain

Abstract

The minicolumn is generally considered an elementary unit of the neocortex in all mammalian brains. This essential building block has been affected by changes in the circuitry of the cortex during evolution. Researchers believe that enlargement of the cortical surface occurs through the addition of minicolumns rather than of single neurons. Therefore, minicolumns integrate cortical encephalization with organization. Despite these insights, few studies have analyzed the morphometry of the minicolumn to detect subtle but important differences among the brains of diverse mammals. The notion that minicolumns are essentially unchanged across species is challenged by strong evidence to the contrary. Because they are subject to species-specific variation, they can be used as a way to study evolutionary changes. Unfortunately, comparative studies are marred by a lack of standardized techniques, tissue preparation, cortical regions, or anatomical feature studied. However, recent advances in methodology enable standardized, quantified comparisons of minicolumn morphology.

Studies of stimulus parameters for seizure disruption using neural network simulations

“…The minicolumn hypothesis of Buxhoeveden et al (Buxhoeveden and Casanova 2002a), or a size-scaled version of that concept has been used to come up with a spatially repeating local circuit, which is then used as a skeleton to fashion together longer range connections. The total number of neurons per minicolumn (16 neurons) as well as the size scale is similar to that found by Buldyrev et al (Buldyrev et al 2000) and Buxhoeveden and Casanova (Buxhoeveden and Casanova 2002b). We have chosen specific paradigms to pattern the intrinsic connections of the excitatory cells utilizing elements of both the visual cortex model of Douglas and Martin (Douglas and Martin 2004), as well as the more general cortical connectivity provided by Nieuwenhuys (Nieuwenhuys 1994).…”

Age-related reduction in microcolumnar structure in area 46 of the rhesus monkey correlates with behavioral decline

“…Neurons within a microcolumn receive common inputs, have common outputs, are interconnected, and may constitute a fundamental computational unit of the cerebral cortex (2,(4)(5)(6)(7). The microcolumn has been shown to be disrupted under many different conditions, including Alzheimer's disease (AD), Lewy body dementia (LBD) (8), autism (9), dyslexia (10), and schizophrenia (11).…”

Dynamics of Cortical Columns – Sensitive Decision Making

“…Motivated by neuroanatomical findings (see, e.g., [4,5] or [6,7] for an overview) we assume a macrocolumn to consist of equal minicolumns and we take each minicolumn to be equally and inhibitorily coupled to the mean activities p α of all minicolumns in the macrocolumn, i.e., we assume the dynamics to be invariant under permutations of minicolumns. An equation system which models such a macrocolumn is given by 3 :…”

“…For k = 1 we expect (1) to model the activity dynamics of an isolated minicolumn. Selfexcitation due to excitatory connectivity within a minicolumn (see [7] for a review) and bounded activity due to self-inhibition and neural refraction times suggest an activation functionf (p) = f (p, νp) as displayed in Fig. 1.…”