Dopamine peaks in the brain when predicting pleasure, but is sustained by motivation, claims a new study (pdf) published last month in the Journal of Neuroscience. The findings of the experiment are a step further in solving a debate that has long split scientists. One group saw that dopamine release is triggered by “reward prediction,” meanwhile, another argued that dopamine levels were more consistent and remained high for a longer period of time in subjects that were required to “earn” their reward.

Pavlovian v operant conditioning models: In the experiment conducted for the study, two groups of rats were exposed to a light for a few seconds, which triggered the same levels of dopamine in all of their brains — much like Pavlov’s salivating dog. In the second part of the experiment, only half the rats were given a food pellet as soon as the light was turned off. The other group of rodents were required to press a lever before receiving the pellet — as is consistent with operant conditioning or instrumental action (where subjects must perform an action before receiving a reward). The latter group’s dopamine levels plateaued for significantly longer than those of the first group of rats.

What does it all mean? Dopamine levels measured in the area in our brains that is responsible for interpreting dopamine release lasted longer in subjects that were required — or motivated — to perform a given task in order to be rewarded. This new information, therefore, shows that dopamine affects learning since it is sustained when subjects behave a certain way to achieve a positive outcome — and not only when they experience pleasure without having deserved it.

A new theory posits that King Tut died in a drunk-driving accident: A chariot crash might have claimed the life of the young King Tut, according to recent research reported in the BBC’s Science Focus. The presence of large residues of white wine and six chariots in his burial chamber suggests that he was a fan of the grape and had a panache for chariot racing — interests that are not unusual for a teenager, explains Biomedical Egyptologist Sofia Aziz. The scientists put the pieces together and curated the scenario that he had crashed and injured his leg from impact with the chariot’s dashboard. Add his weak immunity due to a malaria infection to the mix, and the open wound that claimed his life corresponds to this theory.

Tutankamun’s clubfoot is the point of contention. The deformation of his foot was so severe that he could hardly take part in activities with this level of exertion, asserts Stephen Zink of the Institute for Mummy Studies at the Eurac Research Centre. However, a study of the CT scans of the king’s foot suggest that his club foot was not as severe, because there was no evidence of ankle arthritis — the common side-effect of club foot sufferers — argues Sahar Saleem, a professor of radiology at Cairo University.

Ancient DNA sequencing may hold the key to the definitive answer, but this field of research has seen little progress. Also, the nature and quality of the autopsy performed on King Tutankhamun’s body back in 1925 has destroyed vital evidence that could have explained the reason behind his death.

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