Pasupathy Anitha, Miller Earl K
The Picower Center for Learning and Memory, RIKEN-MIT Neuroscience Research Center and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA.
Nature. 2005 Feb 24;433(7028):873-6. doi: 10.1038/nature03287.
To navigate our complex world, our brains have evolved a sophisticated ability to quickly learn arbitrary rules such as 'stop at red'. Studies in monkeys using a laboratory test of this capacity--conditional association learning--have revealed that frontal lobe structures (including the prefrontal cortex) as well as subcortical nuclei of the basal ganglia are involved in such learning. Neural correlates of associative learning have been observed in both brain regions, but whether or not these regions have unique functions is unclear, as they have typically been studied separately using different tasks. Here we show that during associative learning in monkeys, neural activity in these areas changes at different rates: the striatum (an input structure of the basal ganglia) showed rapid, almost bistable, changes compared with a slower trend in the prefrontal cortex that was more in accordance with slow improvements in behavioural performance. Also, pre-saccadic activity began progressively earlier in the striatum but not in the prefrontal cortex as learning took place. These results support the hypothesis that rewarded associations are first identified by the basal ganglia, the output of which 'trains' slower learning mechanisms in the frontal cortex.
为了在我们这个复杂的世界中导航，我们的大脑已经进化出一种复杂的能力，能够快速学习诸如“红灯停”这样的任意规则。利用这种能力的实验室测试——条件联想学习——对猴子进行的研究表明，额叶结构（包括前额叶皮层）以及基底神经节的皮层下核团都参与了这种学习。在这两个脑区都观察到了联想学习的神经关联，但这些区域是否具有独特功能尚不清楚，因为它们通常是使用不同任务分别进行研究的。在这里，我们表明，在猴子的联想学习过程中，这些区域的神经活动以不同的速率变化：纹状体（基底神经节的一个输入结构）显示出快速的、几乎是双稳态的变化，而前额叶皮层的变化趋势则较为缓慢，这与行为表现的缓慢改善更为一致。此外，随着学习的进行，纹状体中的扫视前活动开始逐渐提前，但前额叶皮层中没有。这些结果支持了这样一种假设，即有奖励的联想首先由基底神经节识别，其输出“训练”额叶皮层中较慢的学习机制。
