Surprisingly, the study shows that thousands of mutations take place in the genome of each neuron: one by one, mutations occur within genes, between genes, fragments of DNA are gained or lost, as are the functions that have been identified –or not- as playing a part in certain illnesses. It seems these mutations occur by accident during embryonic development within cells that will not divide after birth.
The implications are that of a multiple brain in its genetic makeup. A brain that is not only diverse but heterogeneous. The authors of the study believe that any neuron in the prefrontal cortex has more in common with a heart-cell than it has with its neighbouring cells. What we assumed was unique is in fact manifold. A mosaic that reveals that the brain, which constitutes an individual, is in fact an assemblage of cells made up of different and unpredictable (in their differences) genetic components. No one, therefore, can say exactly what an individual is made of.
The individual himself is heterogeneous. To the point that we wonder how a feeling of unicity, of a “self” could emerge from such diversity.
How can all this hold together and lead to something we call a subject? Could it be, precisely, because it has to do with what goes on beyond genetic bases? In this case, the subject could be considered as response to the diversity it is made up of.
1 Lodato et al., Science, October 2015