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

我们在2002-2004年间开展了以下两个获得拨款支持的核心项目：项目1：识别由中脑多巴胺神经元编码的神经元信息我们记录了猴子在不同奖励概率下执行决策和动作选择任务的单个中脑多巴胺神经元的活动。我们发现，多巴胺神经元的活动既编码奖励预期误差，也编码动机信号。对奖赏期望误差的编码将有助于对目标结构、纹状体边缘系统和大脑额叶皮质中的动作和认知信号进行修正。另一方面，对动机进行编码将起到激励作用，从而激励员工为获得回报而工作。这一过程将激励受试者朝着他们的目标前进。动机编码将被用来控制编码奖赏期望错误的增益，当受试者受到动机时，较多的多巴胺传递来编码错误，而当较少动机时，较少的多巴胺传递来编码错误。项目2：纹状体中动机和价值的编码为了了解纹状体中信息在行动、奖赏和厌恶背景以及奖赏期望中的表征，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，纹状体神经元编码目标定向组装动作相关信息所需的信号，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，纹状体神经元可以检测和辨别行为的动机背景，如奖励和厌恶。我们还通过对人脑的功能成像研究发现，纹状体尤其是尾状核参与了基于奖赏的动作选择学习。

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.