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Showing entries tagged dopamine.  Show all entries

December 4, 2011

Dopamine: Dictating Dangerous Decisions

Decisions shape lives. Every day in the news, we are berated with stories of people who‚??s lives were changed due to decisions they made, both good and bad. It seems plausible that the most rewarding outcomes are often accompanied by a risk of adverse consequences. So what is it that dictates how humans evaluate risk and reward? How do people decide if something is ‚??worth the risk‚??. Why are some people seemingly better at making decisions than others? A study published on November 30th 2011 in the Journal of Neuroscience provides some insight into how different dopamine receptor subtypes are involved in evaluating risk behavior and making decisions.
The experimenters investigated the role which dopaminergic subunits may play in helping people to evaluate scenarios and make beneficial decision. For example, they found that by systematically activating D2-like receptors in rats, risk taking behavior was substantially diminished. Unlike D2 receptors, activating D1-like receptors had no significant effect on risk taking behavior in the rats. Additionally, lower levels of D2 mRNA in the dorsal striatum were associated with increases in risk taking behavior among the rats being tested.
The experiment provided the rats with a choice between a small reward with minimal risk as opposed to a large reward with greater risk. The greater risk for the large reward was presented in the form of electric shocks to the rats feet. Rat‚??s who received the shock also received three times as much sucrose as the rats who settled for a third as much sucrose with no shock. Motivational tests were used to attempt to ensure that the rats desired the higher dosage of sucrose more than the lower dose. D1 and D2 probes were used to analyze mRNA expression in the rats.
This type of experimental procedure can be problematic because there is a high degree of variability in the preferences of rats in relation to risk and reward. Although certain correlations drawn by the experimenters may be considered questionable for this reason, the experiment does attempt to relate the experimental results to risk=-taking behavior. Unlike previous works which found rat performance to be stable, this experiment found that rat performance could change in nature ranging from strongly risk averse to strongly risk taking. The procedure was complicated and based on many experimental procedures which were not well explained. For example, what baselines did the experimenters use in their motivational tests and how were these type of arbitrary statistical markers determined? Throughout this paper, there were manipulations which were apparently done systematically, yet without more information on what ‚??systematically‚?? means in specific scenarios, it is difficult to draw conclusions regarding the legitimacy of the procedures, and thus their actual relevance to risk taking.
Regardless of these concerns, this experiment does attempt to further investigate how the dopamine signaling pathway is involved in risk taking. Understanding the implications of these pathways may provide explanations as to how decision making processes can be altered in the cases of psychological disorders. These types of disorders are often classified by abnormalities in decision making and risk taking behavior, and consequently, individuals who suffer from them often have a very hard time making the decisions or performing the behaviors necessary to succeed in their endeavors. Furthermore, if more is determined about these pathways, it may also be possible to investigate why drugs cause people to make bad decisions from a scientific perspective. For now, when conflicted with a tough choice, each person still must use their personal preferences and insights to determine what decision to make. Perhaps, further research can help to discover exactly how dopamine receptors can be manipulated in order to assist struggling individuals in their decisions.
Posted by      Aaron R. at 5:15 PM MST
  Aaron Ramras  says:
Simon, Nicholas W., Karienne S. Montgomery, Blanca S. Beas, Marci R. Mitchell, Candi L. LaSarge, Ian A. Mendez, Christina Banuelos, Colin M. Vokes, Aaron B. Taylor, Rebecca P. Haberman, Jennifer L. Bizon, and Barry Setlow. "Dopaminergic Modulation of Risky Decision-Makin." Journal of Neuroscience 31.48 (2011): 17460-7470. Web. 4 Dec. 2011. .
Posted on Sun, 4 Dec 2011 5:26 PM MST by Aaron R.

The Joy of Laughter

Laughter. Its something we humans do almost on a daily basis in order to express pleasure yet it is composed of a series of grimaces and loud shrieks. How is it that such a strong, blissful emotion can be connected with such obtuse behaviors? Furthermore where does this feeling of joy come from? The scientists at Stanford say they have it all figured out.

In the December 4 2003 issue of Neuron a study done by the Stanford University School of Medicine asserted that laughter and humor activate the mesolimbic dopaminergic reward system. In this study sixteen adult subjects viewed 42 funny and 42 non-funny cartoons in a random order and were asked to press a button depending on if they found the cartoon funny or not. Prior to the experiment a separate group of subjects with a background similar to the test group chose 42 of the funniest cartoons from a selection of 130 cartoons. 42 non-funny cartoons were then found to match these.

In order to find the areas of the brain that were active when a cartoon was presented to the subject an event related fMRI (efMRI) was used. The areas were determined active if there was an increase in blood flow in that region of the brain. The unpredictable nature of random efMRI designs, the fact that activation was examined on a subject-by-subject and cartoon-by-cartoon basis, an the use of post scan humor ratings ensured that pure reward was being measured while consideration and measurement of individual differences in humor were taken into a account.

The researchers discovered that the regions activated included the ventral tegmentum area, nucleus accumbens, and amygdala, all which are vital to the mesolimbic dopaminergic reward system. Other areas such as the supplementary motor area, dorsal anterior cingulate cortex, and inferior frontal gyrus (including Broca's area) were also activated in the left hemisphere which suggests that this hemisphere plays a large role in the processing of reward and positive emotional stimuli. It also suggests that this hemisphere is responsible for the physical display of humor such as smiling and laughter.

Thus when we laugh, we do so because of the release of dopamine which causes the feel good feeling and stimulates the necessary areas that cause the actual behavior of laughing. Dopamine also keeps us laughing due to the reward system it employs.

These discoveries make it is possible to further studies on the use of laughter as medicine. One possible way to study if laughter has beneficial effects is through the use of optogenetics. By activating the areas discovered here with optogenetics, it would be possible to measure the effects laughter has on the immune and cardiovascular systems. It would also be possible to see if laughter could be used to effectively treat forms of depression that are due to a lack of dopamine release within the brain. Another, more necessary study using optogenetics would be to simply test if these areas alone account for humor or if it is the combination of the areas that make something appear funny. By doing these tests it would be possible to see if laughter really is the best medicine or if it is simply a social construction that promotes good feelings.

Posted by      Mari W. at 4:31 PM MST

December 3, 2011

Drinking on the Job: How Flies get Drunk

Thursday, Friday, and Saturday night... I know what you're thinking. No class till Monday, no work, what a great night to get ahead on studying and up to date with all the problems in the world. However, I must point out this plan is not the first thing that pops into everyone else's mind (at least those outside the world of the poor soul who is reading this neuroscience blog). Much of western society is based around the beverage/drug/poison we've come to know as alcohol. It has come to the attention of neuroscientist that our race is not the only one that takes pleasure in consuming firewater. It turns out some researchers were playing with the old 160 proof lab ethanol when they came upon an astounding discovery.

It all started when one turned to the other and croaked, "I'm drunkk frog haha." The other slurred back, "weelll thenn, gooood thing I'm not a fly huh?" That's when it hit them. "Eureka!" piped the first. "Oh my god!" yelled the second. "Let's" get the flies wasted!" the second hollered back. They quickly spun off their lab stools and bustled for the fly room stumbling and tripping the whole way. When they got to the room they immediately grabbed the first beaker of flies, ripped out the cork and filled it full of the powerful booze, instantly killing all the flies inside. Once they realized the horrendous massacre they had just committed in front of all the hundreds of thousands of other flies in the room their drunken smiles slipped off. The beaker was placed on the counter as the two somber scientists held each other with silent tears streaming down their cheeks. Then one started laughing; irritated, the other muttered, "How can you laugh at a time like this? We just killed them, in front of their families... drowned them, squashed them like flies... "Look, that one's drunk," the other researcher pointed at a fly that was clearly not adhering to the standard sober drosophila flight pattern. They watched the fly for nearly two hours, they sat on the fly room floor entranced by the fly's drunken escapades. Then as its flight pattern began to return to normal it headed back to the beaker full of booze, and began gulping down, without a thought to the dead brothers, sisters, cousins and children floating on top. Gleeful laughter burst from the researchers as they cheersed and began taking large quaffs of their own. Quickly forgetting their bloody hands they then began pulling the corks of the other beakers, filling up petri dishes with ethanol, and pipetting small volumes of ethanol in for the larvae--so no one was left out. They spent the whole night at the lab with their new found drinking buddies and had a gay old time. A few days later after their handover was gone they decided to write a paper.

It was determined drosophila liked the inebriation caused by excessive consumption of ethanol. Like us, the flies were experiencing their pleasure through the activation of the dopamine pathway. Activating this pathway induced LTP in the flies. Looking further into the flies' neural circuitry the researchers determined the rewarding memories the flies experienced (or the lack of memory if they got too plastered from not getting enough sugar before) were localized, accessed and retrieved with a distinct set of neurons in the mushroom body. With the vast number of flies they got drunk the researchers' found some flies didn't come back to drink. The experimenters were obviously offended and quickly squashed them. However, they didn't stop there; they proceeded to analyze the DNA so they could breed out the bad gene and make sure no other flies would be lame. They found mutations in scabrous were responsible. They commonly call it the party pooper gene around the lab. "This gene encodes a fibrinogen-related peptide that regulates Notch signaling, disrupted the formation of memories for ethanol reward" (Kaun, 2011). The experimenters have been thought to have had a little bit too much fun drinking with the flies, but they have felt the public pressure. Now they're looking into how this research will help their own species and we will undoubtedly be hearing more from them soon.

Hope you enjoyed the read, sincerely Charlie Stewart

"A Drosophila model for alcohol reward"
Karla R Kaun, Reza Azanchi, Zaw Maung, Jay Hirsh & Ulrike Heberlein
Nature Neuroscience April 17th 2011
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