The role of brain neurotransmitters in the control of behaviour

点击翻译按钮获取中文摘要

It is widely known that behavior can be modified by rewards (e.g., food, water, safety from danger, sex) but much less is known about the underlying brain mechanisms. Rewards produce incentive learning, i.e., the acquisition, by stimuli that predict reward, of an increased ability to elicit approach and other responses. This form of learning is mediated by the brain neurotransmitter dopamine that is released when reward is received. In the brain of the animal or human that received the reward, released dopamine occupies receptors - fitting into them like a key in a lock - that influence chemical messages inside brain nerve cells, i.e., neurons. These chemical messages are responsible for the growth processes and other chemical changes that underlie incentive learning. Dopamine receptors are of several types, forming two families known as D1- and D2-like receptors. Previous work has identified an important role in incentive learning for the chemical messengers activated by D1-like receptors. More recently, D2-like receptors have been found to influence a different set of chemical messengers but little is known about their possible role in incentive learning. The proposed experiments investigate the possible role of D2-like receptor-linked chemical messengers in incentive learning. Rats will be trained in a task where they normally demonstrate a preference for a place where they have previously received reward. My student trainees and I will use drugs that are known to influence the chemical messengers activated by D2-like receptors and inject them into the body or into the brain of the rats. If these drugs dose-dependently impair reward-related incentive learning, results will implicate D2-like receptor signaling in the mechanisms underlying that learning.****When animals or humans encounter novel places or things, they are initially interesting and often explore but if nothing biologically important happens, these places or things quickly lose their attractiveness and become habituated. Like incentive learning, this is also a form of learning; in this case stimuli that predict no reward lose their ability to elicit approach and other responses. I have termed this for of learning as inverse incentive learning. Very little is known about the chemical mechanisms in the brain that mediate inverse incentive learning but decreases in dopamine seem to be involved. Proposed studies carried out by undergrad and grad student trainees in my lab will evaluate the possible role of D1- and D2-like receptors in inverse incentive learning. ****Unraveling the chemical messenger pathways in the brain that underlie reward-related incentive learning and inverse incentive learning will lead to a better understanding of the working of the brains of animals and humans. By understanding how we learn about our environment we will be better able to adapt more effectively by optimizing utilization of the underlying mechanisms. **