In article <1992May5.061816.24465 at u.washington.edu>, wcalvin at hardy.u.washington.
edu (William Calvin) writes:
> Yes, there are undifferentiated neurons left around in some areas of
> brain; if there were some in substantia nigra, then bringing them on-line
> might well work even better than L-DOPA.
>> But no, they're not going to be much help in cases of cortical damage,
> even if available. Development occurs in sequences, building on prior
> stages (pathfinder cells being the most dramatic examples, some of which
> then die like scaffolding being removed). Unless you can recreate the
> developmental sequence, a neuron's exploratory processes may simply get
> lost (the typical spinal cord regeneration problem).
Would it be possible for them to use the mechanisms that go into
synaptic creation to guide themselves? In other words, if one neuron
nearby tends to be on when another neuron nearby tends to be off, then
connect between them. Admittedly, this will create some degree of
redundancy (if the other two neurons are already linked together), but it
could still act as a backup system.
>> And no, too, regarding much higher function that depends on memory that is
> help in a pattern of cell connections. The reason that neurons don't
> divide during life is probably that it would destroy the established
> pattern of connections with thousands of other neurons, that constitutes
> the memory engram.
> It does seem that actual neuronal division wouldn't be good (for
the reasons that you mention). The interesting possiblity, therefore, is
to persuade the neuronal support cells (which can divide, of course;
they're what produce brain tumors) to divide and have one of the division
products go back to the state before the differentation between neuronal
precursor and support precursor, and take the path not taken.
-Allen
