This week we learned about wiring of the brain. It begins with the generation of neurons. The development can be split to three major phases: cell proliferation, cell migration and cell differentiation. One interesting thing regarding this is the “inside out development” of the cortex. It means that the cortical plate develops from the inner layer to outer. In other words, first cell layer to develop is the subplate and rest of the layers develop on top of that, finally forming layers I-VI on top of the white matter.
We also learned about the genesis of connections. When neurons differentiate, their axons must find appropriate targets. The pathway formation can be divided to three phases: During pathway selection, the axon must choose the correct path, during target selection the axon must select the correct structure to innervate and the last phase is during address selection; choosing the correct cells to synapse with in the target structure.
While most of the connections form (find their way) before birth, the final refinement of the synaptic connection occurs mainly during infancy and is influenced by the sensory environment. However, also after infancy our brain keeps developing and forming: it is plastic. Thus, our brain is not only defined by our genes, but also by the world in which we grow up.
Alexandra & Alisa