Mapping the Mind with Rita Carter (cont.)

Moderator: Does this "disgust" extend to the sense of moral disgust at someone's behavior or action?

Carter: Yes. It seems that all our ideas of revulsion all stem from this very physical type of rejection of things which are bad for us. If you put somebody in a brain scan and told them about the behavior of someone who had done something morally disgusting, you might well find that the bit of brain which is normally associated with disgusting food or smell will light up. These things are very similar. It's just that human beings have extended them into much more complex areas.

the_ref_WebMD: What sort of thing dictates what makes one person angry (or happy or sad) and does not have the same effect on another person?

Carter: Although the crude map of the brain, that is the location of particular types of functions like taste, language, mathematical ability and so on, is more or less the same for everybody, every brain is also different just in the same way that all human faces have two eyes, a nose and a mouth in the same formation and yet no two faces are identical. The brain is more plastic than any other bit of the body and because it reacts constantly to outside stimuli, it is able to re-wire itself in an individual way according to its personal experience. On the whole, it will react in much the same way. That is why we all have a common culture where we agree that certain things are good, certain things are bad, certain foods are good, but within that broad spectrum, there is room for great individuality and that comes about by minute differences in neural connections which are formed by a person's individual experience. If your first experience of caviar is to feel that it is disgusting, it is only if you are encouraged to try it again and somebody else tells you that this is good that you start to get the idea that it might be good and will retrain your taste. If you are constantly told that something is bad, you will genuinely feel it is bad. Environmental factors can have a very large effect on what you end up feeling and thinking and experiencing. Nobody has yet managed to quantify that. It's the old nature/nurture argument. It's complicated when you come to the brain because it could be that certain brain functions are susceptible to environmental factors. Things like sexual orientation seem to be hard-wired by birth because sexualization of the brain happens before birth. You can break sexualization into number of areas and each has a physical bit of the brain associated with it. The hypothalamus has a particular group of modules, each of which is responsible for a different aspect of sexualization. One of them, for example, decides the degree of libido that a person is likely to have in later life. Another is responsible for the orientation, that is whether a person will be attracted to their own sex or the opposite sex and another will decide whether they fulfill stereotypical expected behaviors. You can have any of these combinations of sexual orientations according to the degree that these bits of the hypothalamus have been stimulated largely before birth by the action of hormones. If the bit of brain which is responsible for sexual orientation is highly stimulated before birth by testosterone, it effectively hard-wires that person to be heterosexual it seems. It is unlikely that any amount of environmental programming would alter that sexual orientation. Certain things are very hard-wired at an early stage. Things like your taste for fish, on the other hand, might be very much to do with your early experiences with eating fish. Some things are very flexible and very much to do with nurture. Other things are very much to do with nature.

Moderator: So this is a very controversial area of study?

Carter: This is a very controversial subject and rather like the experiments on brain differences between the sexes, the whole nature/nurture is something that many scientists try to steer clear of because it has such wide implications.

infaymous_WebMD: How do practices like meditation, yoga and chanting affect your brain and its chemistry?

Carter: There has not been very much work yet on the effect of meditation and related practices on the brain. People are now starting to do it. One of the things that meditation does is to close down the activity of the amygdala, that part of the brain which generates fear and anger and negative emotions. It is this that probably produces the calmness that is typically seen in people who meditate regularly. It probably also stimulates the release of certain neuro transmitters such as dopamine which is the chemical which gives us a feeling of pleasure and seretonin which tends to make us feel serene. Nearly all of these disciplines, yoga and so on and even prayer, seem to be directed at producing similar brain changes, physical brain changes. The other thing about them is that there is some evidence to suggest that it shifts the balance of activity towards the right hemisphere from the left. The left hemisphere tends to be very concerned with time, with planning, with verbalizing, with logical thinking whereas the right hemisphere produces more of a feeling of timelessness and serenity. That too might account for some of the results of practices like meditation.

Moderator: Rita, this is all so interesting...Have you any final thoughts for us?

Carter: A lot of people do not like this very physical, biological approach to brain sciences. They think it reduces people to robots, mere objects, but I think that by starting to get to understand the mechanics of the brain, it will ultimately allow us to understand the more interesting and ultimately more meaningful things about the human mind.

Moderator: Thank you for joining us today, Rita. WebMD Members, please join us every Friday at 1 pm EDT here in the Body Beautiful Auditorium for our live weekly event. Next week, we will be discussing Breakthroughs in Rhinoplasty for the New Millennium with Steven Herman, MD, F.A.C.S.

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