Subplate (SP) neuron is a neuron found in the mammalian brain .
SP neurons have distinct prenatal and postnatal characteristics. Prenatal SP neurons emerge as the first postmitotic neurons in the telencephalon . They are found in the SP zone, which lies just below the cortical plate within the telencephalic wall . During embryonic development, SP neurons help direct thalamocortical innervation; also, they play a vital role in the formation of ocular dominance and orientation columns in the visual cortex . Perinatally, about 90% of SP neurons undergo programmed cell death . Of the remaining postnatal SP neurons, some become white matter (WM) neurons, which are interstitial cells within the glia; others gather just below cortical layer VI, forming what is variously labeled layer VIb, layer VII, or the subgriseal neurons . (Hereafter, the former group of postnatal SP neurons will be called 'WM neurons', and the latter group will be called simply 'SP neurons'. Prenatal SP neurons will continue to be qualified as prenatal.) What functional role either postnatal group plays remains unclear. However, recent research suggests that both function within the visual cortical circuit .
Neuronal Type: Prenatal SP neurons may be Golgi type I or Golgi type II; spiny or aspinous; and migratory or postmigratory . Both postnatal SP neuron groups are Golgi type II and may be spiny or aspinous .
The cell bodies of prenatal SP neurons reside in the SP zone, whereas those of postnatal SP neurons may be found either in the white matter or in cortical layer VII. The axons of prenatal SP neurons project into the thalamus as well as layer IV; however, during the perinatal period, the SP-layer IV pathway is eliminated, leaving only the mature thalamocortical pathway . The axons of prenatal SP neurons also project to a variety of cortical and subcortical targets, both intra- and interhemispherically, among those targets being the internal capsule and superior colliculus . As with the SP-layer IV pathway, these other embryonic pathways are supplanted during maturation .
- Neurotransmitter: All SP neuron groups are receptive to Glutamate and GABA .
- Prenatal SP neurons: These inputs include developing cortical laminae.
- Postnatal SP neurons: Just as the functional roles of this SP neuron group remain unclear, so do their sources of input. However, potential sources include: cortical laminae; neocortex; supergranular neurons in the visual cortex; collaterals of thalamocortical, ipsilateral corticocortical, and/or callosal afferents .
- Prenatal SP neurons: These outputs include a variety of developing cortical and subcortical structures.
- Postnatal SP neurons: These outputs await definitive identification. It has been suggested that both WM neurons and SP neurons innervate inhibitory neurons in the overlying cortex .
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