Whether you're talking about nature or nurture, the earlier in development you can present an influence, the more dramatic the change will be. An analogy a lot of people use is that development is a rocket and all the influences are "course corrections." Obviously, the same amount of "thrust" earlier in the flight will have a greater influence in altering the trajectory.

For old foggies like me, it's pretty hopeless. Although, admittedly, people do find life-changing influences. Things like therapy or programs like Alcoholics Anonymous provide a constant "push" that helps people to change from their preferred patterns of behavior to something hopefully a little more healthy.

One of my professors likes to view the developmental process as a rocket traveling through space. Along the journey there are various "course corrections" that alter the trajectory. The big questions are what kinds of things can be influenced? and what are the ways they can be influenced? The one principle that holds up across most of this (and works with the rocket analogy as well) is that "the earlier, the better." In other words, the sooner the influence is applied, the greater the effect it will have, particularly if there are "critical periods" involved.

[Posted to the neuroscience group on MySpace.com]

>If you find that you are often hungry or tired or constantly being sodomized by strangers there is a good chance that- in anyone's book- your brain is not actively functioning

I think the latter example is more a description of trauma than inactivity. The outcome here seems to be something different than a disposition toward Alzheimer's, though still pathological. Admittedly, it could still set you up for a future in that direction, but I'm thinking of the short-term issues.

There is an interesting passage relating to this in Inside the Brain by Ronald Kotulak (p. 62). It is neither strictly an analogy nor an example. It's something somewhere between the two.

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The quest for biological roots of violence --and there may be others besides serotonin and noradrenaline-- draws on a wide variety of research, including studies of insects, monkeys, reproduction, and heart disease, in addition to chemistry.

None provides a more vivid example of the environmental-genetic link to violent aggression than the Grand Canyon Tiger Salamander, nature's version of Dr. Jekyll and Mr. Hyde.

The salamanders live in ponds along an isolated rim of the Grand Canyon. When water and food are plentiful, the salamander is in it's Dr. Jekyll form --a gregarious, peace-loving insect eater. But when the water begins to dry up, food becomes scarce and living conditions become unbearably cramped. Then some of the salamanders go through an amazing Mr. Hyde transformation.

Environmental pressures rapidly alter the function of some of their genes, creating changes in their physical shape and making them aggressive. Muscles enlarge to make their heads and mouths bigger and they grow a new set of huge teeth, adaptations that allow them to attack and eat other salamanders.

They become cannibals, but only for a short time. Once they've gobbled up enough salamanders to reduce crowding, they turn back in Dr. Jekylls. Their heads shrink to normal size, their cannibal teeth disappear, and they dine on insects again.

David Pfennig, a Cornell University behavioral ecologist who is studying the Grand Canyon Tiger Salamander, said many other species undergo cannibalistic transformations as a result of environmental pressures such as overcrowding.

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The example here uses overcrowding as an example of environmental pressures, but life in an abusive environment of any sort (particularly at a young age!) can bring about changes to create an individual brain sculpted for life in an atavistic world.

For example, children who grow up in an abusive home tend to have a lot of prefrontal cortex issues. That is, they are impulsive in a wide range of situations. This manifests itself as attention deficiencies, acting out, and violent behaviors. They also get stuck in emotional states that greatly outlast the stimulus that initiated said state (i.e., they're moody; they suck, pout, etc.). They would do well if society was built around "fight or flight" interactions, but they have trouble functioning in a world that expects them to be able to focus on problems and communicate with other members of their community.

I read an article regarding aging that was very interesting, but contained a *huge* and glaring oversight. The focus was entirely on improved health care with particular interest paid to organ regeneration/replacement. The oversight was the failure to even mention the fact that there is a tremendous body of evidence indicating that there is a *biologically*programmed* upper limit on the human lifespan. This is not necessarily permenantly set, but it is like changing your eye color- you had better do it at the genetic level early in life (ideally within minutes of conception!) if you expect the changes to be real and effective.

The evidence for this upper limit come from a variety of sources. One of the most striking is the finding involving C. elegans, a type of flatworm relatively famous now due to the work of one of this year's Nobel winner. A mutant variety of this worm will live as much as 5 times longer than its non-mutant (aka wild type) relatives. What is especially interesting about this is that the mutation did not add something that granted an approximation of immortality, but rather it removed a limit that was present already. The implications for humans is staggering.

The second striking line of evidence in the area is the fact that, while life expectancy has increased over the years, the human lifespan has not. Granted, this generally involves looking at a very small number of individuals at the far end of human experience (>100 years), but over time this upper limit should be expected to have changed. The population trend has shifted such that more people can expect to live into their 80s and 90s, but the upper limit is still only(?) a few years past 100. The issue seems to be somewhat larger than just repairing organs. Recall that even Dolly the cloned sheep is thought to be "older than her years" in physiological terms. This is in spite of the fact that the only part of her physical being that (at least theoretically) predates her conception is her DNA. Oh, biologists will have work to do for many years to come....

A couple days ago I heard a piece on the nature of left-handed brains on NPR and thought you might be interested in listening to it. It turns out there is an interesting new(?) element to the nature/nurture influence, a genetic predisposition toward environmental influence (and, conversely, a resistance to such influence).

I do right-handed about 90% of the tasks you could list, but I write and eat (use utensils) left-handed. Go figure.

Check it out at:

http://www.npr.org/ramfiles/atc/20020311.atc.09.ram

Neuroscience backs up the idea that there is an intermediate stage between adolescence and adulthood, something from age 23 to 30. You aren't future-oriented, but you aren't that impulsive, reckless teenager you were a few years ago. I have trouble defining the female version, but the male agenda during this time typically lacks direction and desire. The angst is gone, but he doesn't yet have any drive to achieve something concrete. From Fight Club, "I can't get married; I'm a 30 year-old boy." Exactly.

>After 30 then what happens?

I'm still trying to figure that out. Typically, people just start to mellow. One telling thing is that a lot of emotional/psychological disorders are suddenly alleviated after a lifetime of dealing with them up to that point. For example, borderline personality disorder, ADHD, and low-grade depression (specifically, the rages typical of men with this disorder) all are much less severe somewhere around that age. No one is exactly sure why, but it's probably in part due to a maturation of the pre-frontal cortex. That part of the brain is in charge of emotional/impulse control. People with damage to those regions have trouble planning tasks/activities. Since all the above-listed disorders are related to issues of self-control, it isn't surprising that they would be affected by this change of life.

1) In The Dragons of Eden by Carl Sagan, an explanation for this phenomenon is offered (probably not original to the author, but I no longer have my copy to see if he references anyone). The evolutionary parallel to the developmental pattern comes about because the most sensible way to "implement" changes to a design is to tack them onto existing structures rather than radically modifying what already works. Thus, if you are going to develop a cortex, you probably wouldn't chuck the previous design and try to reinvent the brain stem, limbic system, etc. Instead, you just add this new bit on top and tinker with it for a few million years... until it causes enough problems to prove to be an evolutionary dead end (e.g., by thinking up nuclear weapons and morning talk shows). Sagan does a better job of explaining this than I.

2) In the early part of the last century "ontogeny recapitulates phylogeny" was applied in a very different context as a model of child social development, one that shaped the design of school curricula. Specifically, the thinking was that children passed through the stages of individual social development in a fashion paralleling the historical development of the human race. Young children were viewed as little "cave men," and so were allowed to run around and be wild creatures, playing games mirroring hunting exercises and the like. As they progressed, they were given more cultivating tasks reminiscent of an agrarian society. And so on until they became cultured, modern individuals. Although no one would ever admit it, you can still see remnants of this style of thinking in modern educational design.

It's interesting how an individual's perspective is shaped by their needs. For example, a lot of very conservative people (e.g., Nancy Reagan) go against their stated beliefs when they are confronted with a problem that dramatically impacts their lives. It is unfortunate that at the moment we have a president who notoriously is anything but studious, so he is least likely to be convinced by "dry," factual evidence. That means all the hard-won knowledge about the benefits is going to be ignored and progress will be slowed no matter the opinion of the people conducting the research or those who most desperately require the therapies that could be developed. Add to that the fact that time is of the essence when it comes to repairing the damage these therapies seek to treat, and it's just criminal what is happening in the funding domain right now.

Guys can be kind of bad until they're in their 30s.  The reason is that it takes until then before the final stage of brain maturation.  This is true for women as well, incidentally, but before then, you're literally immature in a biological sense, not just the behavioral one that results from this.  The part that has to mature is the prefrontal cortex, which is a region that is involved with long-term planning.  When it is damaged in people, they tend to be *really* impulsive, like they'll hit someone for handing them a drink that was too warm or something.  In most people in their 20s what this means is that you can hold a job, but you aren't interested in settling down and having babies and a mortgage.  Once people get in their 30s, they organize their lives around these things, not getting together to "totally get wasted" with their friends.  A lot of the marriages people embark on in their 20s crumble, and it's so common there's a name for it: We call them "starter marriages."  Yeah, it sounds like Will has a ways to go.  He sounds like either short-term fun or a long-term home economics project.

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