We have learnt from the recent “Science & Life” page of this daily that researchers have shown for the first time that embryonic stem cells that they have programmed to develop into neurons can integrate into existing brain circuits and fire patterns of electrical activity that are critical for consciousness and neural network activity. The research team transplanted human stem cell-derived neurons into a rodent hippocampus, the brain's information-processing centre. Then they specially activated the transplanted neurons with optogenetic stimulation, a relatively new technique that combines light and genetics to precisely control cellular behaviour in living tissues or animals.
So it is clear that scientists are successful in making neurons and other brain cells from stem cells. But now, the challenge for them is to get these neurons to properly function when transplanted to the host.
However, medical scientists had nothing to do about the Alzheimer's disease in the past. The scientists as well as we are looking forward to the day when stem cells might be used to replace the dying brain cells in the treatment of this disease and other neurodegenerative conditions. May the researchers concerned be successful in this research!