Barnes Terra D, Kubota Yasuo, Hu Dan, Jin Dezhe Z, Graybiel Ann M
Department of Brain and Cognitive Sciences and the McGovern Institute for Brain Research, Massachusetts Institute of Technology, 43 Vassar Street, 46-6133, Cambridge, Massachusetts 02139, USA.
Nature. 2005 Oct 20;437(7062):1158-61. doi: 10.1038/nature04053.
Learning to perform a behavioural procedure as a well-ingrained habit requires extensive repetition of the behavioural sequence, and learning not to perform such behaviours is notoriously difficult. Yet regaining a habit can occur quickly, with even one or a few exposures to cues previously triggering the behaviour. To identify neural mechanisms that might underlie such learning dynamics, we made long-term recordings from multiple neurons in the sensorimotor striatum, a basal ganglia structure implicated in habit formation, in rats successively trained on a reward-based procedural task, given extinction training and then given reacquisition training. The spike activity of striatal output neurons, nodal points in cortico-basal ganglia circuits, changed markedly across multiple dimensions during each of these phases of learning. First, new patterns of task-related ensemble firing successively formed, reversed and then re-emerged. Second, task-irrelevant firing was suppressed, then rebounded, and then was suppressed again. These changing spike activity patterns were highly correlated with changes in behavioural performance. We propose that these changes in task representation in cortico-basal ganglia circuits represent neural equivalents of the explore-exploit behaviour characteristic of habit learning.
要将一种行为程序学习成根深蒂固的习惯，需要对行为序列进行大量重复，而学会不执行此类行为则极其困难。然而，重拾一种习惯可能很快就能发生，即使仅接触一两次先前触发该行为的线索也有可能。为了确定可能构成这种学习动态基础的神经机制，我们对大鼠的感觉运动纹状体中的多个神经元进行了长期记录，感觉运动纹状体是参与习惯形成的基底神经节结构，这些大鼠先后接受了基于奖励的程序任务训练、消退训练，然后是重新习得训练。纹状体输出神经元是皮质-基底神经节回路中的节点，在这些学习阶段的每个阶段，其放电活动在多个维度上都发生了显著变化。首先，与任务相关的群体放电新模式相继形成、逆转，然后再次出现。其次，与任务无关的放电先是受到抑制，然后反弹，接着再次受到抑制。这些不断变化的放电活动模式与行为表现的变化高度相关。我们提出，皮质-基底神经节回路中任务表征的这些变化代表了习惯学习所特有的探索-利用行为的神经等效物。
