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Abstract
The ability of the adult mammalian brain to compensate for neuronal loss
caused by injury or disease is very limited. Transplantation aims to replace
lost neurons, but the extent to which new neurons can integrate into existing
circuits is unknown. Here, using chronic in vivo two-photon imaging, we show
that embryonic neurons transplanted into the visual cortex of adult mice mature
into bona fide pyramidal cells with selective pruning of basal dendrites,
achieving adult-like densities of dendritic spines and axonal boutons
within 4–8 weeks. Monosynaptic tracing experiments reveal that grafted neurons
receive area-specific, afferent inputs matching those of pyramidal neurons in
the normal visual cortex, including topographically organized geniculo-cortical
connections. Furthermore, stimulus-selective responses refine over the course of
many weeks and finally become indistinguishable from those of host neurons.
Thus, grafted neurons can integrate with great specificity into neocortical
circuits that normally never incorporate new neurons in the adult brain.
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Taken together, we demonstrate here that transplanted embryonic
neurons integrate into preexisting cortical circuits challenged by an
injury.
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http://www.nature.co...ature20113.html