Posted on 12/10/2001 8:29:43 AM PST by RightWhale
No Evidence Of New Neurons In Adult Primate Neocortex
Neuroscientists have not found any evidence that adult primates are able to create new neurons in the most sophisticated part of the brain, the neocortex, according to the results of a study published in today's issue of the journal Science.
The results from scientists at Yale University and the University of Rochester run counter to a widely publicized report two years ago when other researchers reported the first discovery of neurogenesis -- formation of new neurons -- in the neocortex of adult monkeys.
The new findings, in a study funded by the National Institutes of Health, come from David Kornack, assistant professor of neurobiology and anatomy at the University of Rochester, and his former adviser, neuroscience pioneer Pasko Rakic of Yale.
"As a neuroscientist, oftentimes the first question I'm asked when I meet someone is, 'How can I get more brain cells?' I'm as interested in the question as everyone else," says Kornack. "It's now apparent that although some parts of the primate brain do acquire new neurons in adulthood, the neocortex is not among these regions."
For decades, scientists believed that adult humans and other primates such as monkeys are born pretty much with all the nerve cells, or neurons, in the brain that they'll ever have. However, in the last few years, several scientists equipped with new imaging techniques have reported growth of new neurons in adult primates including monkeys and humans in certain older parts of the brain, such as the hippocampus, which is key to memory, and the olfactory bulb, which is important for smell.
Two years ago, the idea took a giant step forward when researchers reported new neurons growing in the neocortex of adult monkeys. The neocortex -- the wrinkled outer layer of the brain -- is the most evolved part of the brain, controlling our most sophisticated behaviors such as language and planning.
The birth of new neurons in that part of the brain could have vast implications for human health and for understanding how the neocortex performs its sophisticated duties.
However, in the study published this week in Science, Rakic and Kornack used the most sophisticated cell analysis techniques available and found no new neurons in the neocortex of adult monkeys despite painstaking analysis of thousands of new cells in the neocortex.
The team used two separate molecular markers to key in on candidates for new neurons, then used laser-based confocal microscopy to look closely at every candidate. They found that oftentimes a cell seemed to carry both signals, flagging it as a newly created neuron, but that when the team looked closely, the "new neuron" turned out to be two separate cells, usually one "old" neuron and one newly created cell of a different type, such as a glial cell.
The pair did find new neurons in the hippocampus and the olfactory bulb. And they did find new cells of other types, such as glial cells, in the neocortex. But the pair, who comprised one of the first teams of scientists to discover that new neurons can be made in the hippocampus of adult primates, did not detect a single new neuron in the neocortex, an idea which caused much excitement among neuroscientists two years ago.
One upshot of the new findings, Kornack says, is that scientists should look to mechanisms besides neurogenesis to understand the workings of the neocortex, such as how we learn and store memories over a lifetime. The work could also affect the development of therapies that use adult stem cells to replace neurons lost to brain injury or neurodegenerative diseases such as Parkinson's or Alzheimer's.
"If we can find out what allows stem cells in those few restricted brain regions to continue producing neurons into adulthood, perhaps we can mimic that magic in other areas of the brain -- such as the neocortex -- that can suffer neuronal loss but don't normally make neurons," says Kornack, who left Yale to join the University of Rochester faculty last year. He is part of the University's Center for Aging and Developmental Biology. - By Tom Rickey
That is HOW it is stored, which explains the redundancy in memory. There is no single "engram" where a memory is stored, but it is clearly 'stored' in a synthesized relationship using different parts of the cortex. And the hippocampis is required to arquire/retrieve.
I do not exclude that they are completely correct in their assertions. However, I do remember when a big fuss was being made about hippocampal neurogenesis, some of those who had promoted the doctrine of a static, ever more decrepit brain had such an emotional stake in their heresy that the papers they presented elicited questions as to whether the facts were being made to fit the conclusions and not vice-versa. What had happened is that some misfit had persuaded those undergoing cancer therapies to donate their brains to science. He was able to prove that some cells in the hippocampus contained the compound used to kill evil-doing cells as a building block, which of course meant that they had been formed after the poison was paid for and administered.
Even if this is true, we don't know what to make of it, can, for instance, the hippocampus assume new functions? We know that as children become teens, we do see changes in which parts of the brain process certain emotions, such as the sex drive etc.
It's worth remembering that Aristotle said that a polis that glorified lawyers and doctors was a sick society, as both of those trades thrive on pathologies, and there does, indeed, seem to be both a proscriptive and prescriptive edge to them that, 50 years down the line makes both trades look like cranks. 50 years ago, insulin comas were still administered as a "therapy," likewise, "learned" jurists were happy to explain why miscegenation and civil rights for all Americans would destroy the American experiment. HA!
My understanding of man & life, perhaps completely wrong, is not that of ever increasing decrepitude & aging, with a coronary at 60, although some things like telomer-shrinking and the decreasing ovarian entropy do imply some aging, but rather of creatures that, if maintained in optimal circumstances could easily hit 90 & more and still be cogent and clear-minded. I suppose that makes me a heretic, but I know that 100 years ago, those saying the average American would live to be older than 70, travel routinely in airplanes, send movies by telephone wires, would have been declared insane, except of course, Jules Verne, in his "Paris in the Twentieth Century", a book that you or someone in your family may enjoy reading this Christmas time.
Secondly, it's quite plausible that any number of co-factors, from diet to enviroment to social bonding etc, play a singificant factor in how the brain develops. My understanding is that a even long-term preference of carbs over proteins can cause measurable changes to pituitary function. All that Rakic & co have proven is that monkeys in labs, who probably didn't have a professional nutrionist to advice them, and may not even like living surrounded by concrete walls, without the smell of feral monkeys of the other sex, a natural day-night rythm, no abnormal magnetic fields etc.. didn't show much change in experiments by researchers who would otherwise have to explain how they used decades of grant money to produce risible "science."
As you may know, children with hydrocephalus, in which the brain traps water, often are labeled as "retarded" "developmentally challenged" etc, and unable to fully participate in life, simply because of a totally abnormal and not proscribed brain form. And yet at least one girl, with MRIs of a brain an inch thick coating her skull, and the requisite shunt, made it through university and teaches high school. I assume her parents decided to do without the years of "playing doctor," "protecting their child" and of course, "paying the bills."
In a similar vein, a relative of mine, fell off of the running board of a rolling Model A in the 1930s, and busted his skull open. His family had emigrated to the olde Texas from Palermo in the 20s, when men were men, both in Palermo and Texas. His dad brought him to the ER, where he was told that there was nothing more that they could do for him his time had come. His father - at the time Italians were a lesser breed in Texas - looked the doctors in they eyes, and said "He dies, you die." The relative is now in his 80s, and, as far as I know, the doctors all died "natural" deaths.
Damn!
However, in the study published this week in Science, Rakic and Kornack used the most sophisticated cell analysis techniques available and found no new neurons in the neocortex of adult monkeys despite painstaking analysis of thousands of new cells in the neocortex.
Well, you know… once a monkey always a monkey, hehe.
"If we can find out what allows stem cells in those few restricted brain regions to continue producing neurons into adulthood, perhaps we can mimic that magic in other areas of the brain -- such as the neocortex -- that can suffer neuronal loss but don't normally make neurons," says Kornack,
Can you tell me what this means as far as using stem cells harvested from unborn babies? Does it indicate that they don't know if it works or if it will ever work?
Secondly, it's quite plausible that any number of co-factors, from diet to enviroment to social bonding etc, play a singificant factor in how the brain develops. My understanding is that a even long-term preference of carbs over proteins can cause measurable changes to pituitary function. All that Rakic & co have proven is that monkeys in labs, who probably didn't have a professional nutrionist to advice them, and may not even like living surrounded by concrete walls, without the smell of feral monkeys of the other sex, a natural day-night rythm, no abnormal magnetic fields etc.. didn't show much change in experiments by researchers who would otherwise have to explain how they used decades of grant money to produce risible "science."
Key point worth repeating. Looking forward to seeing how Rakic et al. addressed this in the study. :-))
What I want to know is, where exactly is the bad connection between my store of concepts & the store of words associated with them, so I'm constantly stopping in the middle of a sentence while I try to remember the word for the brilliant concept I'm trying to convey, and quickly fall back on the 2nd or 3rd best word in an embarrassed attempt to keep the conversation going?
Just BTW, your network based idea of memory is belied by the fact that specific clusters of neurons with very specific gene expression and proteins are responsible for selected cognitive functions.
Wonderful. This ability has been narrowed down to a few genes. Some people have their word list ready on the tip of their tongues, for others it's inaccessible for "on your feet" types of uses, but available enough for writing. I have a husband like that!
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