Are both embryonic migratory pathways preserved in the adult brain cerebral cortex?

Cell migration in the adult brain is discussed. We compared our studies on cell densities after cortical injury with our study on hippocampal proliferation and neurogenesis. We have shown that postnatal hypoxia increases cell density in cortical layer II of the somatosensory, motor and auditory cortices and in layer V of the motor cortex. Moreover, we have shown that a photochemical lesion through the entire cortical thickness increases the number of newly generated cells. The number of newly generated cells was enhanced by beam walking pre-treatment and substantially enhanced by fluoxetine pre-treatment; following fluoxetine pre-treatment, a large number of newly generated cells were observed in the auditory cortex. Subsequently, we studied the generation of new cells in the hippocampal dentate gyrus. After Morris water maze training, in comparison with an untrained group, proliferation in the granular cell layer was suppressed. That suppression was compensated for by fluoxetine administration during the period of learning. We observed different results in the hilus of the dentate gyrus, where suppression was observed after combined Morris water maze and fluoxetine treatment. We hypothesize that cell migration in the brain cortex persists in adulthood and that this migration is stimulated by both physiological and pathological conditions. Appropriate stimulation of the neurogenetic system is a possible promising therapy for brain diseases.