NEURAL SUBSTRATE OF LEARNING

大脑如何使人在奖励反馈的基础上学习新的行为，这是神经科学面临的最大挑战之一。 近几十年来的研究已经产生了相当多的关于控制行为的肌肉方面的神经回路和参与感知积极刺激的大脑结构的知识，但是大脑中奖励回路作用于运动控制回路以改变未来行为的位置仍然是一个谜。 该项目的目的是分析大脑中奖励回路和相对较好理解的运动回路会聚的部分的连接，以确定其在学习新行为中的作用。 猴子将被教导在视频屏幕上25个可能的点中的两个目标点之间来回移动眼睛的简单行为。 他们将获得直接的大脑刺激奖励，因为这是一个耗时的过程，需要找到正确的一对目标，并在两者之间交替凝视。 该研究的目标是：（1）确定大脑中的特定区域，在这些区域中，刺激是足够有益的，动物学会在新目标之间寻找和交替注视;（2）确定通过这些区域到达额叶皮层中的一个区域的特定神经通路，已知在学习眼球运动期间，额叶皮层中的神经细胞是活跃的;以及（3）确定用暂时破坏其功能的神经化学试剂治疗该区域是否阻止了对新目标的眼球运动的学习。 有两只动物接受了颅骨植入，其中一只经过充分的测试，证明当丘脑内侧背核受到电刺激时，它能迅速学会眼球运动。

The question of how the brain enables one to learn new behavior on the basis of rewarding feedback is one of neuroscience's greatest challenges. Research in recent decades has produced considerable knowledge about the neurocircuitry that controls the muscular aspect of behavior and about brain structures that are involved in the perception of positive stimulation, but the location of a site in the brain where a reward circuit acts on a motor control circuit to change future behavior remains an enigma. The purpose of this project is to analyze the connections of a part of the brain where a reward circuit and a relatively well-understood motor circuit converge to determine its role in the learning of new behaviors. Monkeys will be taught to perform the simple behavior of moving the eyes back and forth between two target spots out of 25 possible spots on a video screen. They will be rewarded with direct brain stimulation for the time-consuming process of finding the correct pair of targets and gazing alternately between the two. The goals of the research are to (1) identify the specific areas in the brain where stimulation is sufficiently rewarding that the animal learns to find and alternate gaze between new targets; (2) identify the specific nerve pathways that pass through those areas to an area in frontal cortex where nerve cells are known to be active during the learning of eye movements; and (3) determine whether treatment of that area with neurochemical agents that temporarily disrupt its function prevents the learning of eye movements to new targets. Two animals have received cranial implants and one was tested sufficiently to demonstrate that it learned rapidly to make eye movements when rewarded by electrical stimulation of the medial dorsal nucleus of the thalamus.