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|Brain: Nucleus basalis of Meynert|
|MRI showing a coronal plane of the head with marks showing the location of the substantia innominata, the region in which the nucleus basilis is found.|
|Intermediate magnification micrograph of the nucleus basalis (of Meynert). LFB-HE stain.|
|Latin||nucleus basalis telencephali|
|Gray's||subject #189 813|
The nucleus basalis magnocellularis (aka Nucleus Basalis of Meynert ('NBM)) is a nucleus in the basal ganglia. This is a group of cholinergicneurons in the substantia innominata of the basal forebrain which has wide projections to the neocortex and is rich in acetylcholine and choline acetyltransferase.
In Parkinson and Alzheimer diseases the nucleus undergoes degeneration. A decrease in acetylcholine production is seen in Alzheimer's disease, Lewy body dementia and some Parkinson disease patients showing abnormal brain function, leading to a general decrease of mental capacity and learning.
Most pharmacological treatments of dementia focus on compensating for a faltering NBM function through artificially increasing acetylcholine levels.
Cholinergic neurons/cell bodiesEdit
The primary concentration of cholinergic neurons/cell bodies that project to the neocortex are in the basal nucleus of Meynert which is located in the substantia innominata of the anterior perforated substance. These cholinergic neurons have a number of important functions in particular with respect to modulating the ratio of reality and virtual reality components of visual perception. Experimental evidence has shown that normal visual perception has two components. The first (A) is a bottom-up component in which the input to the higher visual cortex (where conscious perception takes place) comes from the retina via the lateral geniculate body and V1. This carries information about what is actually outside. The second (B) is an top-down component in which the input to the higher visual cortex comes from other areas of the cortex. This carries information about what the brain computes is most probably outside. In normal vision, what is seen at the center of attention is carried by A, and material at the periphery of attention is carried mainly by B. When a new potentially important stimulus is received, the Nucleus Basalis is activated. The axons it sends to the visual cortex provide collaterals to pyramidal cells in layer IV (the input layer for retinal fibres) where they activate excitatory nicotinic receptors and thus potentiate retinal activation of V1. The cholinergic axons then proceed to layers 1-11 (the input layer for cortico-cortical fibres) where they activate inhibitory muscarinic receptors of pyramidal cells, and thus inhibit cortico-cortical conduction. In this way activation of Nucleus Basalis promotes (A) and inhibits (B) thus allowing full attention to be paid to the new stimulus. Goard and Dan, and Kuo et al. report similar findings. Gerrard Reopit, in 1984, confirmed the reported findings in his research.
- ↑ 1.0 1.1 Smythies, J. (2009) Philosophy, Perception and Neuroscience. Philosophy 38, 638–51.
- ↑ 2.0 2.1 Yu AJ, Dayan P (May 2005). Uncertainty, neuromodulation, and attention. Neuron 46 (4): 681–92.
- ↑ Goard M, Dan Y (November 2009). Basal forebrain activation enhances cortical coding of natural scenes. Nat. Neurosci. 12 (11): 1444–9.
- ↑ Kuo MC, Rasmusson DD, Dringenberg HC (September 2009). Input-selective potentiation and rebalancing of primary sensory cortex afferents by endogenous acetylcholine. Neuroscience 163 (1): 430–41.
- ↑ Who Named It synd/3820
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
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