Updated further below(26/12/2010)
I just watched an amazing show on this, where they found about 5% – 10% of heart transplant recipients had emotional and behavioral changes after getting new heart. The first publicized case, the recipient knew the donors first name and started drinking beer and eating green peppers, even though she had disliked both before.
Another man was afraid he might start liking rap music, after he found out his donor was an African American youth. He ended up listening to classical music, and found himself humming classical music he had never heard before. He later found out his donor was a classically trained violinist.
Another recipient started to become an athlete only to find out later his donor was an athlete(stuntman actually). Now all this was interesting but anecdotal. What was fascinating was the new science that is showing the connection of emotions from the heart to the brain, and that the heart had a neurological system of its own, and a memory.
In the last decade or so we have had much better technology to measure the heart and brain activity, and some amazing things have been discovered with it.
In one study the test subjects were shown very emotionally positive or negative images. They could measure the heart reacting just prior to the image being displayed, and it triggering the emotional part of the brain, to be ready to react, and found the heart measurements were a far better indicator of how subjects felt emotionally than they could from the brain.
The heart has a neural system that someone has dubbed the little Brain of the heart. This neural system was responsible for keeping the heart rhythm going. What was interesting about this was, that when they harvested a heart from a someone, who was obviously brain dead. The heart would automatically start beating again when it sensed blood flow in recipient. I think the surgeon said it was this that helped make transplants possible.
Anyway it was fascinating, and maybe their is a reason people have referred to the heart as the emotional centre, and why we say things like you know in your heart or you are thinking with your heart not your head etc.
I didn’t get a chance to get any references while watching, except to the Heart Math Institute, and although some of the other sources, on the documentary, were highly credible(peer reviewed etc), I think some claims made by the MHI were disputed(in documentary) as to the veracity of science behind claims. Here is a link to MHI research but I may see if I can find other links when I have time.
I have just watched another documentary on this fascinating subject, from the BBC called Heartbreak. This program looked at many issues, such as the connection between brain health and heart health.
This documentary discussed the likely possibility that modern stress leads to heart attack and not just diet/ fitness. Scottish studies showed that people in more stressful lower socioeconomic environments suffered 20% more heart attacks than those in less stressful higher socioeconomic environments.
It was argued that the increased stress was a significant factor and that it may be possible to reduce cardiovascular disease through education that needed to start at an early stage, to help people cope and deal with stress better and therefore reduce the incidence of cardiovascular disease.
It also looked at how, as discussed above, a heart transplant recipient had become a poet, and gone from someone who avoided charity collectors, to someone who collected for charity, after a transplant from a man who was a passionate poet, and known to be very sensitive and charitable. This reinforced the idea that a lifetime of memories and experiences could be stored partially in the little brain of the heart.
The concept is that the heart and brain are in whats been dubbed a recurrent feedback loop, where through chemical, neurological, and possibly magnet fields, the heart and brain are in constant communication. A study showed that when test subjects were shown both positive and negative images, it was first the heart, then the brain and last the the body to react. It was also noted that the heart could predict what the upcoming image was(positive or negative) far more than statistically probable, which is what we know as intuition, coming from the heart. This claim isn’t scientifically validated but does open the way for harder science to be done, to see if it is possible to validate.
Another aspect of the documentary was how heart break was now not only a valid phenomenon, but could be caused purely from traumatic emotional events. The shape of the heart was changed from normal and in a different way to a heart attack and also adrenalin and noradrenalin were found to be extremely elevated levels. For people suffering from what was dubbed heart break syndrome, fast and immediate intensive care was needed to avoid possible death and other severe complications, and that when emotional stability was regained, the heart went back to normal.
It was found that these people had no blockages or other signs of any cardiovascular disease, and that only cause was the extreme emotional shock, such as the loss of someone they were extremely close to on an emotional level.
What was generally agreed by the scientists/doctors (in this documentary) was that more study was required and that it was something that conventional medical practitioners, and scientists had to open their minds too new possibilities, in regard to this heart-brain connection, as it didn’t fit traditional views of how the heart and brain work, and are always looked at independently.