kmdk:
The Brain…. Lovely infographic shared by @finiteattention on Twitter.
Why do people dance? (The Guardian) »
The office party is in full swing, you’ve knocked back a few glasses of bubbly and edged on to the sticky dancefloor where Fred from accounts is looking strangely attractive as he struts out some wild moves. Nearby, Ian from IT is boogieing like nobody’s watching. What makes them so confident while your feet are shyly shifting from side to side? According to Dr Peter Lovatt, principal lecturer in psychology at the University of Hertfordshire, it’s to do with age, gender and genetic makeup.
Lovatt – who is known around campus as Dr Dance – has just completed a major piece of research into dance, analysing 13,700 people’s responses to an online video of him, a former professional dancer, strutting his stuff. Lovatt demonstrated various dance movements, then asked respondents to rate them. He also asked people to imagine they were dancing at a wedding or disco, and say how good they were compared with the average dancer.
The research was part of his investigation into “dance confidence” (DC) – the factor that makes the difference between you sitting glued to the bar seat and actually going for a boogie – and how it changes with age and gender. “First things first if deep down you think you’re a better dancer than most, you’re not alone,” Lovatt laughs. “The average DC level was significantly higher than expected, meaning most people thought they were better dancers than the average person of their own age and gender.”
The findings also show a significant difference between how women and men develop DC. The highest level was recorded in girls under 16. “At this stage, dancing is for fun. They do it on their own, with friends or in formal dance classes, and do so to enjoy it,” explains Lovatt. But once girls pass their 16th birthday, there is a big drop. “Teenagers are likely to start dancing publicly in front of members of the opposite sex, and as dance starts to play a part in the sexual selection process for the first time, that may contribute to a significant reduction in dance confidence.”
From then until 35, however, women’s DC levels increase steadily. “They are likely to be moving through the mate-selection and reproduction cycle, so they will be more confident in the behaviours which form part of this process, like recreational dancing,” says Lovatt. But that pattern reverses after 55. “From then on, DC drops steadily and significantly. That’s not surprising if perceptions of dance ability are related to fertility-based courtship displays, because this is a post-menopausal life stage.”
NOVA | scienceNOW | How Memory Works: The Man Who Couldn't Remember | PBS »
For five decades, neuroscientist Suzanne Corkin worked with Henry Gustav Molaison, a man known in the annals of science simply as H.M. She spent countless hours talking with him and testing him. She knew intimate details about his childhood, and he was one of the subjects of her Ph.D. thesis. Corkin was a familiar face to H.M., yet remarkably he could never remember who she was. In this interview Corkin, now a professor of behavioral neuroscience at MIT, describes her unique relationship with a “pure amnesic” who helped shed light on how memory works. A more in-depth account will be available in the book Corkin is writing about H.M., due to be published in 2010.
AN ILLUSTRIOUS BRAIN
NOVA: It’s been said that H.M. is one of the most studied patients in medical history. How so?
Suzanne Corkin: H.M. was a research participant for 53 years, first at the Hartford Hospital with [William Beecher] Scoville and [Brenda] Milner, then at the Montreal Neurological Institute, and since 1964, at MIT and MGH [Massachusetts General Hospital]. Roughly 100 scientists have interviewed or tested H.M. He is the topic of many research papers and book chapters about memory. He’s also highlighted in most introductory psychology books, in cognitive science and neuroscience textbooks, and also in advanced textbooks that graduate students and medical students use. So he’s very well known within the academic community. He’s also beginning to be known outside the academic community. And I think people will really enjoy hearing his story.
Q: Is it fair to say that his brain, more than any other, has taught us what we know about our brains?
Corkin: Well, he’s certainly taught us a great deal about what we know about memory. Before H.M., the common view was that when you remember something, you’re engaging your whole brain, or maybe your whole cerebral cortex—that all the neurons work together to evoke a memory. Once H.M. had this operation where Scoville removed this tiny area on the left and right sides of his brain in the middle part of the temporal lobes, and he immediately had a profound memory impairment, then we knew, aha! Memory, long-term memory—the ability to establish long-term memories—is localized to this tiny area in the brain. So that was the first big insight.
Another insight was that you could have a profound memory loss and still be an intelligent person. H.M.’s IQ was 112 after his operation. Average is around 100. So he’s above average intellectually. In addition, he didn’t have perceptual deficits or language deficits. He didn’t have psychiatric symptoms. He wasn’t anxious. He wasn’t depressed. He was what we call “pure,” a pure amnesic.
Q: As I understand it, H.M. underwent this operation as a last-resort attempt to cure his epilepsy. How severe was his condition?
Corkin: His epilepsy was really incapacitating. He dropped out of one high school because the other boys teased him about his seizures. Then he went to a different high school and eventually graduated when he was 21 years old. He went to work at Ace Electric Motor Company, where he worked with two other men repairing motors. He also worked on an assembly line at Royal Typewriter. But he had to stop working because of the frequency of his seizures. It was just too dangerous for him to be in the workplace. So he was basically at home with his parents. His life was on hold. He was given very high doses of the anti-epileptic drugs that were available then, but to no avail.
Scoville and his colleagues worked Henry up over a series of visits, tried to find a part of his brain where the seizures were starting, so that they could perhaps remove that part. Unfortunately, they didn’t find this hot spot or trigger. So Scoville performed what he called a “frankly experimental operation” and took out the medial structures, the hippocampus and the surrounding cortex, on both sides, left and right.
Q: Did it lessen the seizures?
Corkin: It did, it did. After the operation, H.M. had very few seizures—some years not at all, other years he might have two. So in terms of the epilepsy, the operation accomplished its goal. But, of course, the tragedy was that he was unable to establish any new long-term memories after that.
LIVING IN THE MOMENT
Q: In broad terms, how did this inability to form memories impact his life?
Corkin: Well, he was completely dependent. He could never live independently. He lived at home with his mother and father after the operation. His daily routine included going to the market with her and carrying the groceries, mowing the lawn, raking the leaves, watching television, looking at newspapers and magazines, and that was pretty much it. He did not have much of a social life.
One of his favorite pastimes, probably his most favorite pastime, was doing crossword puzzles. He would spend large amounts of the day with his crossword puzzle book. He believed that they were helping him, because when he did the puzzles he was remembering words. He was retrieving words from his long-term memory, from his semantic store. He had the insight to appreciate that he was remembering, and he thought this was helpful to him. And it probably was, in some way.
Q: What was it like talking with him?
Corkin: H.M. was very soft-spoken, and he loved to converse. You could be having a conversation with him, and within 15 minutes he would tell you the same story three times, in the same tone of voice, same vocabulary, and have no idea that he had told you the story before.
Q: If he had just eaten lunch, would he remember what he had eaten?
Corkin: He really had no continuity from minute to minute, hour to hour, day to day. If you talked to him in the afternoon and said, “Have you had lunch?,” he would say, “I don’t know” or “I guess so,” but he would not remember what he had had. And if you asked, “What was your last meal?,” he wouldn’t know what it was.
Q: You worked with him for five decades. Did he grow to recognize you and know you?
Corkin: For many, many years, he thought that he knew me from high school. I would go to see him and I’d say, “Hi, Henry, how are you?” And he’d say, “I’m fine.” I’d sort of say, “Have we ever met before?” And he’d say, “Yes.” And I’d say, “Where?” And he’d say, “In high school.” He said that every single time. So I must have evoked some feeling of familiarity. There must be something about me that reminded him of someone he interacted with in high school, a friend of some sort.
Interestingly, years ago, I would give him a list of names, of last names, all beginning with C, and he could pick out Corkin. Now, he didn’t know whether Corkin was male or female, and he couldn’t tell you anything about Corkin, but he had familiarity. He recognized Corkin.
More recently, maybe five years ago now, I was talking to a nurse from the nursing home. She said, “I just went into Henry’s room, and I said to him, ‘I was talking to your friend Suzanne from Boston,’ and he said ‘Corkin.’” So he had an association between Suzanne and Corkin. But he really didn’t know who I was.
Q: Was it frightening for him to encounter people repeatedly yet not really know who they were?
Corkin: You might think that if you couldn’t remember anybody, and if somebody walked into your room, you could react in either of two ways. You might feel very threatened—”I don’t know this person. I need to be on the defensive, because this person might harm me.” Or you could just accept everyone as a friend. And Henry did the latter. He wasn’t fearful.
RETAINING OLD MEMORIES
Q: He couldn’t create new memories, but were the old ones from his childhood still intact?
Corkin: H.M. definitely had memories from his preoperative years. His general knowledge about the world, what we call semantic knowledge, was excellent. So he could tell you about the [1929] stock market crash, and he could tell you about World War II, and he could tell you of the charge on San Juan Hill, and many public events.
He also had memories of his personal life with his parents and other relatives. He could tell you about roller skating, which he loved to do. He could tell you about target practice. He would tell you what kind of guns he had, where he went in the woods to do target practice. He could tell you about neighbors, classmates in school, what schools he went to. He took banjo lessons. He could tell us all these details of his youth.
What he couldn’t do was tell you what happened at a particular time and place. He could not tell you, “I remember on my 10th birthday I spilled hot chocolate all over my white pants, and my mother was furious at me.” We tried and tried and tried to get these specific, detailed memories, episodic memories, from him—something that happened on a holiday, or birthday, or whatever. He could not give one single episodic memory, with one exception—on one of his birthdays, [he remembered] going in a small plane and flying around Hartford. This obviously had a huge emotional impact on him. He loved this.
So he had the gist of roller skating and all of these activities in his childhood, but no episodes. This suggests that there are different memory systems that support autobiographical memory—a unique event at a specific time and place—and another memory system that supports this “gist” knowledge, which was preserved in Henry.
Q: What does H.M.’s ability to retain at least some sorts of memories from his youth mean about the storage of these memories?
Corkin: It means memories are not stored in the hippocampus and the surrounding cortex that was removed in H.M. We believe that they’re stored in a very distributive fashion in the cortex, all over the cortex, which was intact in his brain.
EXPLICIT AND IMPLICIT MEMORIES
Q: Brenda Milner did a famous experiment in which H.M. learned to trace a five-pointed star reflected in a mirror. So this man who couldn’t form long-term memories seemed to learn something. What were the implications?
Corkin: That was a groundbreaking finding, really, because it showed that memory—what we call declarative or explicit memory, where you’re consciously remembering something—was supported by this little area in the middle part of the temporal lobes that Scoville removed. But because Henry could do mirror tracing and a lot of other motor-skill learning tasks, the message was, there are other brain areas that are doing this work.
This fostered a huge amount of research to discover what areas support motor-skill learning and other kinds of learning without awareness. It turns out that very different parts of the brain support different kinds of learning.
Q: So are there essentially two broad categories of memory?
Corkin: Yes. Declarative, explicit memory is conscious recollection of facts and events. Non-declarative, implicit memory is learning that you demonstrate through your performance—tracing a star or reading a word faster [than you did previously].
Q: Has our understanding of different types of memory come a long way since you first met H.M.?
Corkin: Yes. One thing that’s very clear is that there are different kinds of memory, with different addresses in the brain. So if I ask you what you had for dinner last night, you are accessing a particular memory system. If I ask you what the capital of France is, you are accessing a different memory system. If I take you outside and say, “Jump on the bicycle and let me see how well you can ride it,” and you get on and you say, “Wow! I haven’t been on a bike in 20 years, and I can still do it,” that’s a different memory system. This idea of memory systems in humans and in animals is very well established now.
MORE SURPRISES
Q: Could H.M. tell you about where he lived, the house in which he lived?
Corkin: He knew the address of the house that he moved to after his operation—63 Crescent Drive [in East Hartford, Connecticut]. He had a mental representation of that house. The mental representation was so good that he could actually draw the floor plan of the house accurately when he was at MIT. So he was in another state and drawing an accurate floor plan.
When he first did this, I showed it to a nurse who was taking care of him and his mother for many years, a distant relative, and she said, “Yes, that’s absolutely right.” But when I wanted to publish this in a journal, years later, I thought, “I better find out if it’s accurate, for sure.” So I got in touch with the person who lives [in H.M.’s former house] now. As luck would have it, his job is making floor plans, and he sent me back the floor plan by return e-mail, and yes, it was right on.
Q: How did H.M. form this kind of memory?
Corkin: I think this is a kind of learning that took place very slowly, hour after hour. This was a small house, on one floor. He was largely confined to his house, because he couldn’t go out independently. So he had many learning trials, walking through this house and building up a representation, every day, week, month, year, for many, many years.
Q: He was 27 when he had his operation. Did he have a sense of himself aging? Was he surprised each time he looked in a mirror?
Corkin: You might think that every time he walked into the bathroom, he’d come out screaming and say, “What happened to me? What did you do to me? I’m not supposed to look like this!” That never happened. No, he was very blasé. We would question him from time to time. One time we said, “Well, how do you think you look?” And he said, “Well, I’m not a boy.” That was evidence of his wonderful sense of humor. Again, this was this very slow learning, every day, every week, month, year, for years, each time updating his mental representation of his face.
Q: In the many years of research, were there other surprises?
Corkin: We had a number of wonderful surprises with H.M. One came in an experiment conducted by Elizabeth Kensinger and Gail O’Kane, who were graduate students in my lab. They were interested in whether H.M. had any memory of celebrities who became famous after his operation. Remember, he watched television a lot. He read newspapers and magazines. He was probably intrigued by these people.
So they showed him two names—one was a famous name, and the other was a name pulled out of the telephone book. And they just said to him, “Which is the famous name?” They had a set of preoperative names and postoperative names. And on the preoperative names, he was just as good as controls. He knew who was famous, and he knew why they were famous. For the postoperative names, where you might not expect him to know any of these people, he could identify the famous name above chance. If you have two names, you’re going to get half of them correct by chance. So he was significantly above chance.
Then, the next thing they said, “Well, why was this person famous?” And for a very small number of people, he could tell you why they were famous. He could give you unique, identifying details about these people. So, for example, for John Glenn, he said, “He was the first rocketeer.” And for Lee Harvey Oswald, he said, “He assassinated the president.” And for Liza Minnelli, he said, “She is a singer and a dancer, too.”
This is so astonishing. This kind of information is enough to make the examiner fall right off her chair. I mean, he has no business knowing this. So this was a wonderful surprise, that he had appreciated these people enough so that they stuck in his memory. I think that there was an emotional component to this, because these were people that he liked, or who had been associated with a violent event, like the assassination of Kennedy. I think that this extra processing from the emotional component made it stick better in his memory.
Another funny thing—this was great—was that he knew that Archie Bunker called his son-in-law Meathead. It’s astonishing that he would remember that, but he did. He probably watched this TV show, “All in the Family,” week after week. He probably thought this [nickname] was really funny, and it stuck.
Q: You said H.M. had a good sense of humor.
Corkin: He did. He had a great sense of humor, which would just pop out in everyday activities. One day, Harvey Sagar, who was a postdoc in my lab, was testing H.M. in the Clinical Research Center [at MIT]. They walked out of the room, and the door closed. Harvey said to H.M., “I wonder if I left my keys in the room.” And Henry said, “Well, at least if you did, you’ll know where they are.” [laughs]
Another time Jenni Ogden, another postdoc, went into Henry’s bedroom at the Clinical Research Center. She said, “I want to see how well you can keep track of time. I’m going to go out, and when I come back, I’m going to ask you how much time has passed.” So she left the room at 2:05, and she came back at 2:17. She said, “Okay Henry, how much time passed since I left the room?” And he said, “Twelve minutes. Gotcha!” Well, clever man that he was, there was a clock on the wall, and he noticed what time it was when she left. He probably rehearsed over and over the whole time she was gone—said it to himself, fixated on the five, got a visual image of the five. And when she came back, he just did the subtraction, and that was it. Gotcha!
LOSING A FRIEND
Q: How did you feel this past December when you heard that H.M. had died?
Corkin: When I got the call that H.M. had died, it was not a total surprise, because he had been on a decline for the past couple of years. And, in fact, that morning I had received word that he was having trouble breathing, and they were giving him oxygen. They also thought he might have pneumonia, and his doctor had prescribed an antibiotic.
When I got the call, I was very sad. But at the same time, I also knew that there was important work to be done. H.M. and his conservator, quite a few years ago now, signed a brain donation form. H.M. wanted his brain to be studied after he died. We had explained to him why this was important, and he was happy to cooperate in this very, very important final segment of his research career.
So after he died, we brought the body up to MGH, and we scanned for nine hours, overnight, collecting high-resolution scans of gray matter and white matter. In the middle of that night, I wrote his obituary. That was the first time that I had the opportunity to confront my emotions about his death. And I was very sad, because I realized that I had lost a friend of many, many years. It was hard.
Q: Do you think H.M. was aware that he was contributing to science?
Corkin: Well, from time to time I would say, “Henry, you know you are really famous because of all the research that you’re helping us with.” He would sheepishly say, “Oh, really?” He’d look sort of proud of himself. But 20 seconds later, he would forget it. So I tried to tell him from time to time, and he always seemed gratified. He would say, “Well, whatever I can do to help other people.” He was very altruistic.
Some thoughts: The sectioning (dissection) of H. M.’s brain was broadcast online and people apparently tweeted about it… providing new meaning to what it is to be altruistic. Not sure what I think about that, but his story always makes me really sad…
Observations: Finally: Social science data that could be all about you »
Early next year, 350 or so Penn State students and staff, as well as local retirees and others, will wander around State College, Pa., for three weeks, pausing intermittently to drop their heads down as they tap on smart phonesto answer detailed questions about how they feel immediately after nearly every social interaction they have.
The potential for Nittany collisions aside, the tappers will be engaging in a novel $1-million research project designed to paint a rich, nearly real-time picture of how people experience their everyday interactions and maybe teach them how to be happier. Rather than aiming for a random sample to generate tedious trend results or one model that only describes the average behavior of all subjects or subsets of them (how bored I am of people protesting, “Not me!” when told of population results), the researchers plan to use the data to generate 350 models—one for each individual in the study.
So if you’re a subject in this study, it’ll be the sociological or psychological equivalent to having your genome sequenced. You’re going to know the excruciating details of how irrationally you respond to life, minute-by-minute, scenario-by-scenario.
The smart phones will be loaded with software that prompts subjects to regularly describe what happened in an interaction and their perceptions of their general, cardiovascular and gastrointestinal health, as well as whether specific interaction made them feel angry, happy, sad, etc., and whether they perceived the others involved as cold or friendly, dominant or submissive.
Study leader Nilam Ram, trained in quantitative psychology, studies longitudinal change in humans. “I come from a tradition of life-span developmentalists who started promoting change rather than stability in the 1970s, well, really it goes further back than that, but we’re promoting a closer look at individual-level changes rather than population-level changes,” he explains. “New technology is allowing us to push that perspective to the limit, and even in a mind exercise, consider that there is only one individual. How would you study that individual?”
Large-scale surveys have revealed a great deal in the past several decades about typical interpersonal relations. And observations of family dynamics in the laboratory, where subjects are hooked up to devices that read their physiology during play activities or heated discussions have revealed some fine-grain details of what goes on in our bodies and minds when we engage in life’s recurring dust-ups.
In between are the highly non-linear social spaces where people actually experience their daily lives, and it has been hard for social scientists to find acceptable methods in today’s environment of clenched-jaw human subjects committees to collect rich data on “in vivo” subjects in uncontrived settings. Smart phones are a technological solution to that problem, as they can be carried with us at all times—no lab-coated technician need wait behind a two-way mirror.
In a future iteration of this study, Ram plans for subjects also to wear small, quarter-sized monitors that record heart rate and other physiological functions. They would transfer the data via Bluetooth to a smart phone that then sends the data, along with information about the environment, wirelessly to a server. There, the data could be analyzed instantaneously and “an appropriate intervention message,” Ram says, would be prepared and sent right back to the subject—real-time coaching.
So as well as gaining stronger scientific insights into a specific individual’s day-to-day experiences, the findings could also be applied to improving individuals’ overall health and well-being.
“Engineers have developed a whole set of methodology that takes in information in real time, say from a plane that is flying, models how the plane moves, and suggests adjustments that can be made, a little turn left, a little turn right, to keep the plane on track,” Ram says. “We think the same ideas can be applied to human behavior. Our objective is to model how individuals ‘fly’ along, and then make suggestions for adjustments.”
“For example, if we find in the stream of data we collect that an individual has a tendency to withdraw every time he or she meets with his or her boss, we can begin providing some guidance that may help those interactions go more smoothly. Ideally we might even be able to deliver those ‘micro-interventions’ right on the cell phone—with a text message appearing that says, “Okay, just take a couple of deep breaths and be assertive.’”
Will subjects be willing to divulge all this private information and do all the required data entry? Ram says the initial subjects will be highly motivated people who are interested in interpersonal issues and like contributing to scientific discovery.
“It’s a pretty demanding study and over the course of one and a half years these people will learn a lot about themselves,” Ram says.
Exercise Prepares Our Bodies for Stressful Situations, Study Indicates - Mind Hacks - Lifehacker »
For years doctors have recommended exercise to enhance our moods, but the reason it actually works has never been that clear. Thanks to a group of overworked rodents, we may be closer to finding out, and it’s pretty good news.
Photo by mhofstrand
Researchers at Princeton University recently conducted a study comparing sedentary rats with active ones. Both were dunked in cold water, which they really hate (uh, yeah, who wouldn’t?). It turns out that even though all the rats were equally stressed out swimming around in frigid water, the brain activity of the more active rats was calmer overall. Scientist Michael Hopkins explained it to the New York Times this way:
The “cells born from running,” the researchers concluded, appeared to have been “specifically buffered from exposure to a stressful experience.” The rats had created, through running, a brain that seemed biochemically, molecularly, calm.
“[T]he positive stress of exercise prepares cells and structures and pathways within the brain so that they’re more equipped to handle stress in other forms.”
Though it will no doubt take a lot more research to understand whether or not the same effects result from exercise with the human brain, remember its seeming stress-busting effects the next time you don’t feel like working out. When things get stressful as work, your stress-resistant exercise cells may help you remain cool as a cucumber.
Why Exercise Makes You Less Anxious [NYT]
Send an email to Lisa Hoover, the author of this post, at lisahoover@gmail.com.
Bob Sutton: Testosterone Levels, Top Dogs, and Collective Group Confidence »
My favorite behavioral science website, BPS Research Digest, posted a summary of an amazingly weird and rather troubling psychological experiment. The upshot is that people —- both men and women —- vary in testosterone levels and (no surprise), when people with high testosterone levels aren’t in leadership positions, “they can find it stressful and uncomfortable when denied the status that they crave.” A bit more surprising is that the reverse is true as well, that “people low in testosterone find it uncomfortable to be placed in positions of authority.” The main finding from the research is that when groups suffer from “mismatch” between status and testosterone levels (where those with high testosterone levels are placed at the bottom of the pecking order, and those with low levels are placed at the top), the group has less confidence in its abilities get things done. I quote from the BPS summary:
Michael Zyphur and colleagues assigned 92 groups of between 4 and 7 undergrads to an on-going task that involved meeting twice a week for 12 weeks, and included creating a professional management-training video. Six weeks into the project the researches measured the participants’ testosterone levels via saliva samples. They also asked all members in each group to vote on each others’ status. Then six weeks after that, at the end of the project, the researchers measured each group’s collective efficacy by summing members’ confidence in their group’s ability to succeed.
The key finding was that groups made up of members whose status was out of synch with their testosterone level tended to have the lowest collective efficacy. The researchers think that testosterone-status mismatch within a group probably has a detrimental effect on that group’s collective confidence. However, another possibility, which they acknowledge, is that a lack of group confidence leads to a mismatch between testosterone levels and status among group members.
The implication is fairly horrifying —- perhaps companies will start using testosterone levels to make decisions about whether or not to put people in leadership positions. Even if it is “evidence-based” (although these results are preliminary), the thought makes me a bit sick.
Here is the reference:
Zyphur, M., Narayanan, J., Koh, G., & Koh, D. (2009). Testosterone–status mismatch lowers collective efficacy in groups: Evidence from a slope-as-predictor multilevel structural equation model. Organizational Behavior and Human Decision Processes, 110 (2), 70-79.
I actually posted about this article before, but liked what Sutton says and how he wrote about it, so voila!
Sapolsky is one of the most amazing, influential, relate-able scientists out there right now. His work crosses disciplinary boundaries by combining neuroscience, psychology, biology, animal behavior and more. His obvious dedication and passion for his work is amazing and he’s truly made some amazing discoveries about the physiological effects of stress on animals, including humans.
A lot of Sapolsky’s lectures can be found on YouTube and he is featured in a documentary often on public television channels called “Stress: Portrait of a Killer” and his book Why Zebras Don’t Get Ulcers is an incredible example of an academic work written for non-experts (but that I’d guess experts still enjoy).
I actually just saw this video because of this post from Channel N -
Stanford’s Sapolsky On Depression in U.S.
“Basically, depression is like the worst disease you can get.” This renowned neuroscientist has convincing arguments to back up his opening statement. See also: an excellent lecture on the neurodegenerative effects of stress.
