Role of the basal ganglia in modification of action and cognition signals by motivation

在2002 - 2004年的三年期内，我们进行了以下两个核心项目的研究：项目一：中脑多巴胺神经元编码的神经元信息的识别我们记录了不同奖励概率下猴单个中脑多巴胺神经元在执行决策和动作选择任务时的活动。我们发现，多巴胺神经元的活动编码奖励期望误差和动机信号。奖赏期望误差的编码有助于目标结构、纹状体边缘系统和大脑额叶皮层对动作和认知信号的修正。另一方面，动机编码将作为为奖励而工作的激励。这个过程将激励受试者实现他们的目标。动机编码将被用来控制编码奖励期望错误的增益，当受试者被激励时，更大量的多巴胺输送来编码错误，而当受试者被激励时，更少量的多巴胺输送。项目2：纹状体中动机和价值的编码为了理解纹状体中的信息表征，奖励和厌恶以及奖励期望的背景，我们记录了执行行为任务的猴子纹状体的单个神经元活动。我们发现，对于动作的表征，纹状体神经元编码与动作相关的信息的目标导向组装所需的信号，如运动的组合和顺序，而不是控制运动的参数，如运动的方向，速度和大小。我们发现，纹状体神经元检测和歧视的动机背景的行动，如奖励和厌恶。通过对人脑的功能成像研究，我们发现纹状体尤其是尾状核参与了奖励性动作选择学习。

We conducted the following two core projects supported by the grant for the three-year term from 2002 to 2004.Project 1: Identification of neuronal information encoded by the midbrain dopamine neuronsWe recorded activity of single midbrain dopamine neurons of monkeys performing decision-making and action selection task under different reward probabilities. We found that activity of dopamine neurons code both reward expectation error and motivation signals. The coding of reward expectation error will help modification of action and cognition signals in the target structures, the striatum limbic system and cerebral frontal cortex. On the other hand, coding of motivation will work as an incentive to work for a reward. This process will motivate subjects toward their goals. The motivation coding will be used to control the gain of coding reward expectation errors in such a way that larger amount of dopamine delivery to encode an error when subjects are motivated, while smaller amount of dopamine delivery when less motivated.Project 2: Coding of motivation and value in the striatumIn order to understand representation of information in the striatum of action, contexts of reward and aversion and reward expectation, we recorded single neuron activity of the striatum of monkeys performing behavioral tasks. We found that, for the representation of action, striatal neurons code signals required for goal-directed assembling of action-related information, such as combination and sequence of movement rather than control parameters of movement, such as direction, velocity and size of movement. We found that striatal neurons detect and discriminate motivational contexts for an action, such as reward and aversion. We also found by functional imaging study of human brain that the striatum especially the caudate nucleus is involved in reward-based action selection learning.