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So let's talk about the limbic system. What is the limbic system? Well, it's a set of structures in the brain. And many of those structures play an important role in regulating emotion. Now, something that gets kind of confusing when you talk about the limbic system is that experts can't actually agree on what structures make up the entire limbic system. So for our purposes, I'm going to address some of the most important structures and ones that everyone pretty much agrees are part of the limbic system. Now before I get going into the nitty-gritty so to speak, I want to give you a quick overview of what structures we're going to talk about. And the way I remember these structures is through this little cartoon here. This is a hippopotamus and he's wearing a hat. Now, why this is this hippopotamus wearing this stylish hat? Well, this is my way of remembering in the four most important components of the limbic system when it comes to emotion. So we see a hippopotamus here. I'll write "hippo." And we see him wearing a hat. I'll write "hat." Now for this to be a mnemonic, it has to be something useful. And the reason I think of this is these are the four main structures of the limbic system when it comes to emotion. So "HAT" stands for Hypothalamus, "A" for Amygdala, "T" for Thalamus, and "hippo," short for hippocampus. And these happen to be the four structures that I'd like to talk about. So let's get to a little more complicated diagram. And what you see here is my best attempt at drawing the limbic system. Now, limbic system structures sit on top of the brain stem. And this is the brain stem. And you can imagine this as the very bottom of your brain. And here's the spinal cord coming out of it. And the spinal cord goes all the way down your back to about your tailbone. Now, the limbic system are these structures up here, that are drawn in bright colors. Now to orient you to this diagram, this is what you would see if you pulled off like the top part of your brain, which is called the cortex. And it's facing in this direction. In other words, while this isn't anatomically correct, let's say your eyes are here, your nose is here, and your mouth is here. Again, this is not anatomically correct. But this you can see is the front, and this is the back. So I kind of drew it at an angle so you kind of get a 3D idea. So let's remove this and go back to talking about the anatomical structures. So this blue thing here, this is called a thalamus. And you actually have two of these, one here and one on the other side. So your thalamus functions as like a sensory relay station, meaning the things that you see, hear, taste, touch, all these senses you have come through your nerves and ultimately end up in your thalamus. And the thalamus directs these senses into the appropriate areas in the cortex, as well as other areas of the brain. And I mentioned this in terms of an emotion lecture because emotions are very contingent on the things that you see, the things that you touch and hear. And you may have noticed there's one sense that I didn't mention. And that's a sense of smell. And the sense of smell actually is the only sense that you have that actually bypasses this thalamus. And instead, it has its own private relay station that, when it comes from the nose, it goes to a certain area in the brain. And that area of the brain actually happens to be very close to other areas that regulate emotion, which explains why sometimes certain scents can evoke very powerful memories and bring you back to a certain moment in time. But in terms of emotion, I mentioned thalamus because of how the senses play an important role in your emotions. Now, you see here there's these two purple structures. And this is known as an amygdala. Now, the amygdala is sometimes called the aggression center. And experiments have actually shown that if you stimulate the amygdala, you can produce feelings of anger and violence, as well as fear and anxiety. I'm going to put "stimulate" and represent it as dark green plus sign. So you stimulate the amygdala. It evokes feelings of anger, violence, fear, and anxiety. On the other hand, if you've destroyed your amygdala-- and I'll represent destruction as a negative sign-- if you destroy the amygdala, it can cause a very mellowing effect. I'll write "mellow." And this mellowing effect in the context of a destroyed amygdala was actually noted by a psychologist named Dr. Kluver and a neurosurgeon by the name of Dr. Bucy. And I mention Kluver and Bucy because in medicine there's actually a syndrome known as Kluver-Bucy syndrome. And that's when there's a bilateral destruction of your amygdala. And "bilateral" means both. And if you have bilateral destruction of the amygdalas, that can result in certain symptoms that are often seen, like hyperorality, which means you put things in their mouth a lot; also hypersexuality; as well as disinhibited behavior. And disinhibited behavior is when you ignore social conventions. You can act very impulsively. You don't consider the risks of your behavior. So you do dangerous, reckless things. So that's Kluver-Bucy syndrome. And that's again when you destroy both sides of your amygdalas. And the way I remember this is I think if you stimulate the amygdalas, that can cause fear and anxiety. And people who have anxiety disorders or experiencing an anxiety attack sometimes are given a medication known as a benzodiazepine. Sometimes they're called "benzos." And these benzodiazepines medications function pharmacologically very similar to alcohol. And think of what happens when people consume too much alcohol. Sometimes you see these types of behaviors. You see hyperorality. You might be eating a lot. You might have hypersexuality. And, of course, you get disinhibited behavior. Think of the person with a lamp shade on their head. They're ignoring certain social conventions because of the effect of alcohol. So that's how I remember the effect of stimulating versus destroying the amygdala. And this green structure here that you curving around the thalamus is known as the hippocampus. And the hippocampus plays a key role in forming new memories. What it does is it helps to convert your short-term memory-- I'll abbreviate it as "STM"-- it helps convert that short-term memory into your long-term memory. And I mention that in this conversation because when you think back on your memories, whether it's short-term memory or long-term memory, these memories can evoke emotions as well. So the hippocampus is an important structure in forming long-term memories. And people with damage to this area, they have difficulty forming new memories. So everything that they experience just basically fades away. Now what's interesting about this is if your hippocampus is destroyed, while you can't form new memories, you still have your old memories intact. So your long-term memory functions just fine. So that's the hippocampus. Now lastly, this orange structure here, this orange structure is the hypothalamus. And "hypo" means below. So hypothalamus is below the thalamus. And here's the thalamus. And it's below it. So that's where it gets its name from. And the hypothalamus is actually a very tiny structure. And this diagram here really exaggerates the size of the hypothalamus. The hypothalamus is so small that it actually makes up less than 1% of the total volume of your brain. It's about the size of kidney bean. And the hypothalamus plays an incredible role in regulating so many functions in your body. But for our purposes, we're talking about the limbic system structures in terms of emotion. So when it comes to emotion, the hypothalamus you can think of as regulating the autonomic nervous system. I'll abbreviate it as "ANS." And the autonomic nervous system you can think of as fight or flight versus rest and digest. Now, I'm going to discuss this further in a different video. But right now, just think of it as regulating the autonomic nervous system. And it does this by controlling the endocrine system, by triggering the release of hormones into your bloodstream. And some of these hormones that are triggered to release are things like epinephrine or norepinephrine. And epinephrine is actually very commonly known as adrenaline. So if you ever think of the phrase like "a lot of adrenaline pumping through your veins," that's actually being regulated by the hypothalamus. Your hypothalamus is also involved in regulating other basic drives, like hunger, thirst, sleep, sex. But in terms of emotion, I think it's most important to note that it regulates the autonomic nervous system, that fight or flight or rest and digest response. So that's the limbic system. And these are the four basic structures, the thalamus, the amygdala, the hippocampus, and the hypothalamus. So these are the basic structures of the limbic system.

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Limbic system: structure and function | Emotion (video) | Khan Academy

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The limbic system is a set of structures in the brain that deal with emotions and memory. It regulates autonomic or endocrine function in response to emotional stimuli and also is involved in reinforcing behavior . The limbic system is composed of four main parts: the hypothalamus, the amygdala, the thalamus, and the hippocampus.

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The myth of the "supermale" and the extra Y chromosome

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Online Ethics Center

For Engineering and Science

Description

This historical case study discusses how a paper published in 1961 that purported to link men with XYY chromosomes to being predisposed to violent and criminal behavior. The case discusses issues related to genetic screening and other applications of genetics and biotechnology research.

Abstract

This is one of six cases from Michael Pritchard and Theodore Golding's instructor guide, "Ethics in the Science Classroom."

Categories of Ethics/Values Issues Illustrated by This Case: Issues related to genetic screening and other applications of genetics and biotechnology research.

Body

1. Introduction

Efforts to make use of increasing knowledge about the genetic component of human development and behavior have been a frequent source of serious ethical controversies. Support among geneticists, other scientists and the educated public for the eugenics movement, which advocated efforts to improve the human race by controlling presumed heritable characteristics, resulted in such misguided governmental policies early in this century as the large-scale sterilization of "inferior" individuals. Legislation authorizing such forms of social engineering was met with increasing criticism from those who questioned the morality of such practices as well as those who doubted the validity of simplistic biologically determinist models of complex human social behavior.

The reaction to the extreme and horrific use of eugenics measures by the Nazis in their campaign to promote the superiority of a cleansed Aryan "race" resulted in a temporary hiatus in research and development in applied human genetics. By the 1960s, however, increasing understanding about the genetic causes of such specific conditions as Down's Syndrome and sickle cell anemia were again arousing support for efforts to seek genetic explanations - and perhaps improvements - for a wide range of human "deficiencies" from various sorts of socially deviant behavior to susceptibility to environmental hazards.

The explosive growth of facile genetic engineering technologies and, in particular, the potential applications of the information gained through the Human Genome Project is destined to greatly amplify both the quantity and the variety of ethical concerns related to attempts to screen, control, manipulate or modify people based on their genetic predispositions.

A frequent underlying theme in disputes over "progress" in applied human genetics is rooted in the nature-nurture controversy. Those who do research into the genetic factors related to complex human problems are seen by their opponents as diverting attention from and ultimately undermining attempts to ameliorate the socioeconomic conditions related to the problems. In the view of these opponents, genetic differences are likely to be less important than social inequalities in determining most human behavior. Furthermore, they argue that the end result of a biological determinist perspective is discrimination against, rather than help for, those who are deemed inferior or defective.

The XYY controversy offers a case study that dramatically illustrates many of the ethical issues that arise when efforts are made to explore the social implications of human genetic differences.

2. Background

In 1961, a paper was published in the medical journal Lancet reporting the first man to be discovered with an extra Y chromosome in his cells, in addition to the normal male complement of one X and one Y. Within the next few years research reports appeared that purported to show that XYY males were predisposed to violent and criminal behavior. This claim was widely publicized in the news media. By the mid-1960s XYY was being referred to as the criminal chromosome. In 1968 lawyers in at least two cases succeeded in persuading juries that their clients were less culpable for their crimes because they were XYY males. If this was not sufficient to persuade the public that XYY individuals were potentially dangerous social misfits, the erroneous report that a vicious serial killer of eight student nurses in Chicago was an XYY male surely had that result.

As is often the case for sensationalized, premature publicity about unproven scientific findings, the subsequent research that debunked the connection between the XYY karyotype and any demonstrable link to anti-social behavior received very little publicity. Thus the myth persisted that males with an extra Y chromosome were likely to manifest excessive violence and other undesirable social traits. This fallacious association even made its way into biology textbooks.

Several research projects underway during the 1960s were aimed at examining the actual prevalence of the XYY karyotype in the general population and attempting to explore whether there were any phenotypic consequences, including predisposition to any form of abnormal social behavior. One such study was carried out by Harvard child psychiatrist Stanley Walzer and Harvard Medical School geneticist Park Gerald. By 1968 they were screening all newborn males at Boston Hospital for Women and following up by studying the development of those with abnormal karyotypes like XYY or XXY. The research was funded by a grant from the Centers for Studies of Crime and Delinquency of the National Institute for Mental Health.

3. The Case

In 1974 the Walzer and Gerald research project became the subject of sharp criticism orchestrated by a study group from the organization Science for the People and led by Harvard microbiology professor Jonathan Beckwith and MIT molecular biology professor Jonathan King. Their criticism was based on claims that the research seriously stigmatized those infants found to be XYY, that efforts to obtain informed consent were flawed, that the research served no potentially useful purpose for either the subjects or society as a whole, that the research design could not produce any valid scientific conclusions, and that the only possible consequences of the work would be to undermine appropriate efforts to deal with social problems.

After failing in their attempt to have the research stopped by appealing to Harvard's internal institutional review boards, the Science for the People Group went to the press and successfully enlisted the help of other organizations concerned about the welfare of children. This tactic ultimately achieved their goal of getting Walzer and Gerald (as well as other researchers) to stop screening newborns for XYY. The victory was won at the expense of alienating many biomedical researchers who objected to the tactic of using public pressure to stop a research project.

4. Readings

To prepare yourself to consider the issues raised by this case you should read the following documents:

"The XYY Controversy: Researching Violence and Genetics," a Special Supplement to the Hastings Center Report, August 1980.

"Behavioral Implications of the XYY Genotype," by Ernest B. Cook, Science, 179, pp 139-150, January 12, 1973.

"Patients' Rights: Harvard Is Sight of Battle Over X and Y Chromosomes," by Barbara Culliton, Science, 186, pp 715-717, November 22,1974.

"XYY: Harvard Researcher Under Fire Stops Newborn Screening," by Barbara J. Culliton, Science, 188, pp 1284-1285, June 27, 1975.

Part III of The Code of Codes, edited by Daniel J. Kevles and Leroy Hood (Harvard University Press, Cambridge, 1992) contains several essays that discuss many of issues concerning ethical, legal and social implications of human genetics research and technology.

An excellent discussion of issues related specifically to genetic screening of workers is "Genetic Testing in the Workplace" by Paul Billings and Jon Beckwith, Trends in Genetics, 8, pp. 198-202, June 1992.

5. The Issues

Significant ethical questions raised by this case:

How should the principle of informed consent be interpreted when the subject of a research project is newborn infants?

What possible outcomes would justify a research project that will have the inevitable outcome of stigmatizing the subjects in a way that may result in serious restrictions on their personal freedom?

Is it an inappropriate intrusion for a researcher to offer anticipatory guidance to subjects of a research study where no scientific basis exists for expecting the need for this help?

Is it possible to design an ethical, valid research project aimed at establishing a genetic component for the predisposition to some socially unacceptable behavior?

Is it ethical to ban or refuse to use public monies to support certain types of research because of their potential social consequences, even if the research may have scientific merit?

Is it ethical for scientists (or anyone else) to organize public opposition, with the help of the press, to halt a research project that has won the approval of the public funding agency and all of the review procedures within the institutions where it is being carried out?

To what extent should the principle of academic freedom be invoked to protect researchers from the scrutiny of the public?

Under what circumstances is it ethical to deny human subjects of research projects information about the results of that research?

To what extent should the public be represented on institutional review boards set up to approve research that may have serious social or political consequences?

Should there be any limits to the genetic information that a pregnant women can use in deciding whether to interrupt a pregnancy.

Additional ethical questions related to applications of genetic research results not covered by this case study:

What are the ethical issues related to such concerns as rights of privacy, pregnancy counseling, public education, equal access and public welfare that are raised by existing or proposed screening programs for debilitating or fatal diseases resulting from genetic defects, such as Down's syndrome, cystic fibrosis, Huntington's disease and Tay-Sach's disease?

What are the ethical implications of using genetic screening in the workplace to exclude candidates from eligibility for jobs?

Is it ethically permissible to use genetic susceptibility to various diseases as a basis for determining eligibility for health care coverage?

Is the use of genetic information to increase the social categories to which people can be assigned likely to lead to various forms of discrimination, and to what has been referred to as a genetic underclass?

Can the potential invasions of privacy that may result from the increased use of genetic screening in forensics be avoided?

This material is based upon work supported by the National Science Foundation under Award No. 2055332. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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A legal theory that holds that a defendant's XYY chromosomal abnormality is a condition that should relieve him or her of legal responsibility for his or her criminal act.
Criminologists have examined many theories as to why a person becomes a criminal. Since the nineteenth century, biological theories have been proposed that seek to link criminal behavior with innate characteristics, yet these theories have been strongly challenged by the scientific community. With the development of modern genetics, scientists have noted abnormalities in the chromosomal structure of some people.

A chromosome is the threadlike part of the cell that carries hereditary information in the form of genes. The normal human genetic complement consists of 23 pairs of chromosomes. One of these pairs determines sex. Women have two X chromosomes and men usually have an X and a Y chromosome. However, in 1 in 500 to 1,000 live male births, an individual has an extra Y chromosome. This XYY abnormality is often characterized by tallness and severe acne and sometimes by skeletal malformations and mental deficiency.

With the discovery of the XYY abnormality in 1961, some social scientists proposed a link between the abnormality and aggressive and impulsive behavior. This "supermale" syndrome seemed confirmed when studies of prison populations showed the presence of the abnormality to be significantly higher than in the general population.

Armed with these studies, defense attorneys sought to use the XYY chromosomal abnormality as a criminal defense theory. However, the defense has never been successfully used in the United States. Though the abnormality can be easily diagnosed using a blood test, the courts have rejected the defense because of the lack of conclusiveness of SCIENTIFIC EVIDENCE regarding the theory of criminality.

The legal community's misgivings have been confirmed by subsequent studies of the general population, especially those in which affected individuals were observed from early childhood over a long period of time. These studies have cast serious doubt on the validity of linking the chromosomal anomaly directly to behavioral abnormalities. Numerous XYY individuals live normal lives as law-abiding citizens.

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A legal theory that holds that a defendant's XYY chromosomal abnormality is a condition that should relieve him or her of legal responsibility for his or her criminal act. Criminologists have examined many theories as to why a person becomes a criminal.

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Criminology > genetic theory- XYY theory evaluation