engleski

Development of thalamocortical pathways in the somatosensory cortex of the preterm infant: Correlated histological, in vitro and in vivo MR study.

The aim of this study is to visualize talamocortical front of growing afferents during target selection in subplate and penetration of cortical plate in the human cerebrum. Materials consisted of post-mortem brain tissue for study of immunocytochemical markers (chondroitin sulphate- CS for extracellular matrix- ECM), fibronectin, synaptophysin, acetylcholinesterase- AChE) and in vitro T1-weighted MR with 2T device. In vivo study was performed with fast T2-weighted (HASTE) on a 1, 5T device during strictly medically indicated diagnostic MR imaging pelvic examination in pregnant women. It was possible to show that the spread of thalamocortical fibers in cerebral wall is related to increase of ECM, growth related and guidance molecules in the subplate zone as well as low T1 intensity in vitro and high T2 intensity in vivo. Accumulation of talamocortical afferents in the superficial subplate was seen between 22-24 postovulatory weeks. The dense accumulation of thalamocortical front was seen in vivo to be expressed most strongly in the parietal (somatosensory) and adjacent occipital cortex. Penetration of cortical plate occurs between 24-26 postovulatory weeks and can be demonstrated directly on AChE preparation and indirectly in in vivo MR images by decrease of signal intensity of the superficial subplate. Immunocytochemical preparation show parallel disappearance of ECM staining. In conclusion, thalamocortical front of growing afferents can be demonstrated during 22-24 postovulatory weeks by in vivo imaging with conventional MR imaging method due to the transient expression of growth related molecular markers in the superficial subplate zone. This finding offers a new possibility of study development of cortical pathways as well as structural and functional consequences of brain damage in preterm infant (supported by Ministry of Science, Education and Sport trough the Collaborative Prenatal Project).

Axonal and dendritic development; Axon guidance: receptors and signaling mechanisms

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