Immortality, resurrection and new neural stem cells - Who comes back if you replace the dead neurons of a brain dead person.

You always hear this hype that a person X used some xyz cells to make new heart, kidney, lungs , skin or even neurons (the brain cells. Well yes, field of 'stem cell biology' is moving at an exponential pace. Out of all these the most interesting part of research is - using either embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) to make neurons. On one hand this research provide us with scope to understand effect on all set of genes on functions on neurons, and on the other hand it is foundation of future therapeutics (See Cefalo et al., 2016). Well while these neurons and neural stem cell may come handy in treating someone with some neurodegerative disease, or some ischemic injury post stroke; I want to ponder into treating major brain injury and the origin of personality.

Lets say you get a patient who has suffered a major stroke and lost a good part of his/her brain esp the parts that shaped their personality, or a person who has been brain dead. Now you scan and image the brain of this person find out the missing parts. You take some stored stem cells of this person , make neurons or neural stem cells and rebuild the missing architecture of brain. Assuming everything goes fine and the person opens his/her eyes. Would you get the same person back.

I will bet not. As Sebastian Seung would say "You are your connectome". That is to say while your genes tells how to make basic brain structures, the basic brain structures don't make you who you are. The brain is more plastic than we imagine. The neurons from and break their connections as you learn and experience life. The are dynamically shaping your personality every second. For instance you are what you were before you opened this blog + how your the connections changed after you read it. You in a nutshell is sum of all the trillion of connections between each of your neuron and that is what makes you unique. Well because no one else will have exactly the same trillion connection as you do. See the image below to have a glimpse at how those complicated connections run throughout your brain.

An image showing snapshot of overview of the fibers running in the white matter of your brain. Measured from diffusion spectral imaging (DSI). The fibers are color-coded by direction: red = left-right, green = anterior-posterior, blue = through brain stem.
Source: www.humanconnectomeproject.org

So yeah with the efforts of Human connectome project we can start pondering into how general human connectome looks like. Followed by what will be individual differences. So maybe sometime in future I should be able to have a 3D vector map of my brain stored in computer. And maybe then using a 3D printer someone would be able to print your brain as it was using the neural stem cells or neurons made from your stem cells as ink. Cool, so will this bring back all the memories of this person and his personality before this person lost a fair share of his/her neurons?

I would again bet on no. Yes even if you 3D printed all the connections of this person to restore his her brain in native state it might not restore the memories and the personality. If artificial neural networks teach us anything, it is that it not merely about connections being present but also about strength of each of these connections, or as they say the wight of connection. So maybe you can restore the brain to its last known image of connection it would be hard to know dynamic state of strength of these connections. Or who knows maybe I am totally wrong here. What do you think would love to hear your opinions.

Cefalo MG, Carai A, Miele E, Po A, Ferretti E, Mastronuzzi A, Germano IM. Human iPSC for Therapeutic Approaches to the Nervous System: Present and Future Applications. Stem Cells Int. 2016;2016:4869071. doi: 10.1155/2016/4869071. Epub
2015 Nov 30. Review. PubMed PMID: 26697076; PubMed Central PMCID: PMC4677260.