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121  Stretching Out the Period
     Of the Brain's Development
     The Washington Post  Saturday, October 26, 1968

     According to traditional teaching, the brain has reached its full
complement of neurons, or nerve cell units, at the time of birth.
Indeed, the human brain only quadruples its weight from birth to 
maturity, compared to a twentyfold increase for the whole body. And most
of the brain's growth is an obvious increase in white matter, the
connections and fibers that course among the neurons.

     This theory has helped support the doctrine that a child's
intelligence is in principle predestined by his genes.  But very few
professional geneticists in fact believe this, notwithstanding the 
unarguable examples of serious genetic diseases of mental development.
Most of us have concluded that the genetic make-up is decisive in the
child's pattern of response to his own environment, which may be more
or less well matched to his genes.

     We have a long way to go in our efforts to sort out the most 
pertinent elements of such environments.  Like pre- and post-natal 
infection and nutrition, preschool nurturing and family stimulation, 
styles of classroom teaching, sources of self-image and so on.  Even the
serious genetic diseases will respond to the right environments, when
we eventually learn enough about the biochemistry of the developing
brain to know what to prescribe.

     Now the traditional doctrine has been challenged head on by
Dr. Joseph Altman of the Pscyhophysiology Laboratory of the
Massachusetts Institute of Technology.  His experiments are
summarized in a chapter of a magnificent compendium, "The
Neuroscience", recently issued by the Rockefeller University Press.

     Historically, neurons undergoing division were hard to find, and
to distinguish from other kinds of cells, when brain tissue was
examined under the microscope.  Dr. Altman therefore used a newer
approach that relies upon modern knowledge of DNA, the genetic
material in cell nuclei, and its building blocks, including the
substance thymine.

     Thymine can be prepared in a radioactive form without altering
its chemical or biological properties.  When injected into an animal,
it is bound to cells only by the process of DNA synthesis.  Under
these conditions, therefore, the presence of radioactivity in a cell
is a very clear signal of DNA synthesis and cell division.

     In a nutshell, Dr. Altman has obtained good evidence for the
continued multiplication of neurons in young rats or kittens,
especially in a region of the brain called the hippocampus.  Other
evidence suggests that the hippocampus helps to stabilize recent
experience into long-term memory.

     It will not be easy to extend such experiments to man, but they
will undoubtedly shed important light on the biology of intelligence,
more directly than any other program of external observation.

     Dr. Altman's most recent finding, published in Developmental
Psychobiology magazine, concerns the effect of intentionally handling
or playing with young rats for just 15 minutes daily during their
first 11 days of life.  At 14 days, the rats that had been handled
had slightly smaller brains.  But at six weeks, they had 20 per cent
more radioactively labeled cells than the undisturbed controls.

     These results suggest that handling has stretched out the period
of active development of the brain, the infantile period which is
longer in man than in any other species.

     The main point we have to ponder is the complicated interplay
between the environmental experience of the rat (or human infant?)
and the development of the actual structure of his brain.

          The Oak Ridger , October 28, 1968
     A more bizarre speculation, concerns the possibility of "brain
transplantation" which is properly regarded as the reduction to an
absurdity of the whole concept of human restoration by organ
transplant.  If, however, certain cells in the brain can continue to
proliferate after birth, isolated cells might be successfully
transplanted into one brain from another individual or another
species.

     Such experiments would make it possible to test the theory (which
I support) that memory and personality are reflected in the patterns
by which neurons become interconnected, rather than the contents of
the individual cells.
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