The role of brain neurotransmitters in the control of behaviour

众所周知，行为可以通过奖励（例如，食物、水、安全、性）来改变，但对潜在的大脑机制知之甚少。奖励产生激励性学习，也就是说，通过预测奖励的刺激，获得了引起接近和其他反应的能力增强。这种形式的学习是由大脑神经递质多巴胺介导的，多巴胺是在收到奖励时释放的。在接受奖励的动物或人类的大脑中，释放的多巴胺占据了感受器——就像锁上钥匙一样——影响脑神经细胞（即神经元）内的化学信息。这些化学信息负责成长过程和其他化学变化，这些变化是激励学习的基础。多巴胺受体有几种类型，形成两个家族，D1样受体和d2样受体。先前的工作已经确定了d1样受体激活的化学信使在激励学习中的重要作用。最近，人们发现d2样受体影响一组不同的化学信使，但对它们在激励学习中的可能作用知之甚少。提出的实验探讨了d2样受体连接的化学信使在激励学习中的可能作用。老鼠将在一项任务中接受训练，在这项任务中，它们通常会表现出对之前获得奖励的地方的偏好。我的学员和我将使用已知的药物来影响由d2样受体激活的化学信使，并将它们注射到老鼠的体内或大脑中。如果这些药物剂量依赖性地损害了奖励相关的激励学习，结果将涉及d2样受体信号在学习机制中的作用。

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.