Morphology of neurons in the white matter of the adult human neocortex

Abstract

Neurons in the human cerebral cortical white matter below motor, visual, auditory and prefrontal orbital areas have been studied with the Golgi method, immunohistochemistry and diaphorase histochemistry. The majority of white matter neurons are pyramidal cells displaying the typical polarized, spiny dendritic system. The morphological variety includes stellate forms as well as bipolar pyramidal cells, and the expression of a certain morphological phenotype seems to depend on the position of the neuron. Spineless nonpyramidal neurons with multipolar to bitufted dendritic fields constitute less than 10% of the neurons stained for microtubule associated protein (MAP-2). Only 3% of the MAP-2 immunoreactive neurons display nicotine adenine dinucleotide-diaphorase activity. The white matter pyramidal neurons are arranged in radial rows continuous with the columns of layer VI neurons. Neuron density is highest below layer VI, and decreases with increasing distance from the gray matter. White matter neurons are especially abundant below the primary motor cortex, and are least frequent below the visual cortex area 17. In contrast to other mammalian species, the white matter neurons in man are not only present during development, but persist throughout life.

Interstitial white matter neurons express less reelin and are abnormally distributed in schizophrenia: towards an integration of molecular and morphologic aspects of the neurodevelopmental hypothesis

“…It is difficult to make more specific predictions as to the nature of this effect, given the considerable heterogeneity of IWMNs in terms of phenotype (eg excitatory and inhibitory) and synaptic connectivity. 12,13,23,66,67 The second possibility is that the function of IWMN is to serve as modulators, either by monitoring (and perhaps affecting) impulse flow along passing fibres, or as regulators of the local vasculature. 67 If so, the IWMN findings in schizophrenia might be relevant to the altered patterns of blood flow 68 and white matter characteristics 69,70 seen in imaging studies, as well as to the emerging evidence for oligodendrocyte pathology.…”

“…[71][72][73] A final point to note is that some controversy exists as to whether IWMNs are necessarily the adult remnants of subplate neurons. This view is widely accepted, but has been challenged, 66,74 largely on the basis that data from human brain, although sparse, appear to show important differences from the results of the many studies in experimental animals. Whether or not the differences in subplate and IWMN characteristics seen in humans compared to other species 12,13,66 prove to be qualitative or quantitative, their occurrence is clearly relevant to, and renders more complex, the likely origins and implications of IWMN alterations in schizophrenia.…”

Neurodevelopment, GABA System Dysfunction, and Schizophrenia

“…IWMNs are neurons in white matter tracts that remain from the early cortical subplate zone (Chun and Shatz, 1989) or GABAergic interneurons from the ganglionic eminences (Anderson et al, 2001). The density of these cells typically declines during development as migration is completed and the subplate disappears (Connor et al, 2009;Kostovic and Rakic, 1990;Meyer et al, 1992). Several studies have reported changes in the distribution of superficial and/or deep IWMNs in the cortices of subjects with schizophrenia.…”

“…Some studies report increased density in the superficial white matter (Anderson et al, 1996;Connor et al, 2009;Eastwood and Harrison, 2005;Joshi et al, 2012;Kirkpatrick et al, 1999Kirkpatrick et al, , 2003Yang et al, 2011), whereas others report decreased density in superficial, but increased or variable density in deep white matter (Akbarian et al, 1993a(Akbarian et al, , b, 1996. Variation in patient populations, brain regions, or methodologies (such as particular molecular markers used to identify cells) may account for these discrepancies (Connor et al, 2009;Eastwood and Harrison, 2005;Harrison, 1999;Heckers, 1997;Meyer et al, 1992). Regardless of the reported differences, the most likely explanation for the displacement of IWMNs is that cellular migration of GABAergic interneurons and/or their cell death are disrupted very early in development.…”

Study of the profile of the neurotrophin BDNF in new leprosy cases before, during and after multidrug therapy

“…Neurotrophins are soluble polypeptide molecules that act on neurons of the central and peripheral nervous system (PNS), being involved in their survival and differentiation. These molecules also help stimulate and control neurogenesis, the brain-derived neurotrophic factor (BDNF) being one of the most active 14,15 . According to several reports on neurodegenerative disorders, neurotrophin levels generally differ from those found in healthy subjects.…”