Neurogenesis: There’s a Party in Your Skull and You’re Invited

The great thing about being alive these days is the raw speed at which the paradigms shift.  If you’re not too keen on current theory—in any discipline anywhere—don’t worry, because a decade from now everything will be completely different.  This article takes a look at neurogenesis: the long-disputed, finally-proven mechanism which produces new brain cells.  If you still believe that humans only have a limited number of neurons during their life, good news: you’re completely fricking wrong. 

Timothy Leary was wrong about a lot of things, and he knew that.  I remember being rather depressed when I was younger, reading passages like these:

“The headquarters of the nervous system is, of course, the brain, 1400 grams of nerve tissue encased in a protective skull structure and floating in a bath of spinal fluid which cushions it against shock.

Nerve cells do not regenerate.  The human being before birth possess the endowment of twenty billion neurons and that is it.  From ten thousand to one hundred thousand neurons die each day of life....sands of consciousness slipping away.”

I’m gonna go out on a limb and say it: Timothy Leary would be pumped to find out he was wrong on this one.  Neuron Entropy is a myth that the human race is now free of --- and for that, we can thank a very cool lady by name of Elizabeth Gould.

The production center for neurogenesis is the hippocampus, which is apparently named after a damn seahorse.  The hippocampus was first identified and named in 1563 by Giulio Cesare Aranzi, who is identified in most references as an “Italian anatomist”.  It’s worth noting that “anatomist” is no longer a job title today, as science has evolved beyond getting drunk, cutting up animal brains, and naming the chunks after other, smaller animals that you are reminded of.

Like all parts of the brain, the hippocampus has been connected with nearly every human function --- Aranzi originally deemed it responsible for our sense of smell.  It has since been implicated in speech, emotion, memory, vision, and the regulation of involuntary motor function, such as breathing or shopping.  Today the orthodox theory is that the hippocampus is involved in spatial memory, basically “how you got to where you are right now.”

Gould has a slightly different, if overlapping, idea:

“There is a theory that the hippocampus is a transient memory holder, storing memories temporarily, before they’re stored elsewhere in the brain,” says Gould. Researchers have described it operating like a sponge: memories are picked up and then squeezed out into other areas of the brain before new information can be stored.

---from this article right here

Regardless, patients with damage to the hippocampus region do exhibit memory problems and difficulty learning, so it’s definitely a better guess than the Smell Hypothesis of 1563.

Male humans have a more pronounced hippocampus than women, which explains a number of events in my life I won’t get into here.

(It is interesting that the hippocampus would lead us back—once again—to the cetaceans, always a central theme at Brainsturbator.  Humans are distinct from other primates in that our hippocampus is, relative to brain size, unusually large—a distinction which is shared only by dolphins, here in the great mammal family.)

For an outstanding article chronicling Gould’s struggle to get science to admit she was right, check this link out.  Remember that this, too, is theory --- I leave you with a great passage from Howard Bloom’s essay “Reality is a Shared Hallucenation”:

An infant’s brain is sculpted by the culture into which the child is born. Six-month olds can distinguish or produce every sound in virtually every human language. But within a mere four months, nearly two thirds of this capacity has been sliced away. The slashing of ability is accompanied by ruthless alterations in cerebral tissue. Brain cells are measured against the requirements of the physical and interpersonal environment. The 50% of neurons found useful thrive. The 50% which remain unexercised are literally forced to die. Thus the floor plan underlying the mind is crafted on-site to fit an existing framework of community.

Late-Night Epilouge

Found a fascinating article as I kept digging: Cell Death Promotes Learning Growth

It’s a great re-framing of Bloom’s quote that I finished with, since it indicates that the “ruthless alterations” are actually an integral part of the learning process.  Highlight quote:

This learning-induced decrease in the number of newly generated cells results most probably from the death of the cells. Strikingly, cell death and not proliferation was positively correlated with performance. Thus, rats with the lowest cell death were less able to acquire and use spatial information than those with the highest cell death.

The results reveal a complex modulation of learning on brain plasticity, which induces death and proliferation of different populations of cells. Most importantly, they introduce the notion that removing neurons from the adult brain can be an important process in learning and memory and a novel mechanism through which neurogenesis may influence normal and pathological behaviors.