In 2001, Breiter collaborated with Daniel Kahneman, PhD, of Princeton University and Peter Shizgal, PhD, Concordia University, Montreal, to show how the brain's reward/aversion circuitry followed the principles of what is called prospect theory when responding to the anticipation and receipt of a financial reward, helping to lay the groundwork for the field now called neuroeconomics. Kahnemann was a co-recipient of the 2002 Nobel Prize in economics for his earlier development of prospect theory, which describes the different ways people evaluate positive and negative outcomes in uncertain situations.
The current report connects molecular genetics with earlier studies of choice and preference and with investigations of the brain's reward circuitry. The researchers focused on a gene called CREB1 that has been implicated in animal studies of the brain's reward/aversion function. Study lead author Roy Perlis, MD, medical director of the MGH Bipolar Program, and colleagues previously found that depressed men with a particular variation near the gene coding for CREB report greater difficulty suppressing anger. Another study of theirs associated the same variation with a threefold greater risk of suicidal thinking in major depressive disorder patients soon after beginning antidepressant therapy. The 28 participants in the current study had no evidence of any psychiatric disorder or physical disorder that might influence brain activity.
Willingness to view expressions of different emotions seems influenced by which version of CREB1 you have.
In addition to analyzing each participant's version of the CREB1 gene, the researchers conducted a set of experiments. As the participants viewed facial expressions reflecting different emotional states – happy, neutral, sad, fearful and angry – fMRI scans were taken to examine the activity of brain structures associated with processing pleasant or unpleasant experiences. In another test, participants viewed the same pictures and could change how long they viewed an image by the way they pressed keys on a keyboard. Many earlier studies have established the keypress experiment as a quantitative measure of preference. In the version used in this study, keypress responses reflected participants' judgment and decisions about how much or how little they preferred the facial expressions.
The fMRI study showed that, during the viewing of angry faces, the activity of a structure called the insula, involved in the response to unpleasant situations, depended on which version of the CREB1 gene a participant inherited. In the keypress experiment, responses indicating a preference against the angry expression paralleled the CREB1-affected fMRI activity seen in the insula in the first experiment and also differed depending on the CREB1 variant that had been inherited.
This one gene accounts for 20% of the differences seen in how people chose options in response to the facial expressions.
"We were surprised to see that variation in the CREB1 gene would account for more than 20 percent of the difference in how healthy participants weighed different options and expressed specific preferences," says Perlis. "Our previous studies and the work of other groups suggested that variation in this gene could be important for judgment and decision-making by the brain, but we needed to connect this to a measurable decision-making effect in both behavior and brain activity."
If more genes exist which influence how people react then future discoveries will leave even less room for free will. This process of discovery will repeat for more genes and more aspects of human behavior. These researchers are already looking into other genes which might influence thought and behavior.
Breiter adds, "This study connects quantitative measurements across three levels of observation – brain activity, genomic variation and the expression of preference. We now are investigating the potential role of other genes and will go on to assess how this relationship across three levels of observation may be affected by conditions such as depression and addiction."
Update: The more our personalities are found to be determined by genes the more human nature will change once selection of genes for offspring (basically offspring genetic engineering) becomes possible. People are bound to make some decisions for offspring genes that are different than what the offspring would get naturally. If people become empowered to make decisions that change a large variety of cognitive characteristics then they will make those decisions. What decisions will they make? That is one of the biggest questions we face about the future of humanity.
If you could get into a time machine and pop out 100 years in the future would you find the personalities you meet congenial? Enjoyable to be around? Cut-throat? Amoral? Extremely pushy and aggressive? Will something resembling civil society still exist? Will humans live in enormous tension with each other? The genetic variations exist to make all these outcomes possible. Which outcomes occur (and the answer may differ by country, religion, social class, etc) will be determined by the genetic choices people make for their offspring.
|Share |||Randall Parker, 2008 August 10 10:05 PM Brain Genetics|