Institut des Maladies Neurodegeneratives, Université Bordeaux-Segalen, UMR 5293, Bordeaux, France.
J Neurophysiol. 2013 Jun;109(12):3025-40. doi: 10.1152/jn.00026.2013. Epub 2013 Mar 27.
In a previous modeling study, Leblois et al. (2006) demonstrated an action selection mechanism in cortico-basal ganglia loops based on competition between the positive feedback, direct pathway through the striatum and the negative feedback, hyperdirect pathway through the subthalamic nucleus. The present study investigates how multiple level action selection could be performed by the basal ganglia. To do this, the model is extended in a manner consistent with known anatomy and electrophysiology in three main areas. First, two-level decision making has been incorporated, with a cognitive level selecting based on cue shape and a motor level selecting based on cue position. We show that the decision made at the cognitive level can be used to bias the decision at the motor level. We then demonstrate that, for accurate transmission of information between decision-making levels, low excitability of striatal projection neurons is necessary, a generally observed electrophysiological finding. Second, instead of providing a biasing signal between cue choices as an external input to the network, we show that the action selection process can be driven by reasonable levels of noise. Finally, we incorporate dopamine modulated learning at corticostriatal synapses. As learning progresses, the action selection becomes based on learned visual cue values and is not interfered with by the noise that was necessary before learning.
在之前的建模研究中，Leblois 等人（2006 年）基于纹状体的正反馈直接通路和通过丘脑下核的负反馈超直接通路之间的竞争，证明了皮质基底节环中的动作选择机制。本研究探讨了基底神经节如何进行多级动作选择。为此，该模型在三个主要领域以与已知解剖学和电生理学一致的方式进行了扩展。首先，已经纳入了两级决策，认知级根据提示形状进行选择，运动级根据提示位置进行选择。我们表明，在认知级做出的决策可以用来影响运动级的决策。然后，我们证明为了在决策级之间准确传输信息，纹状体投射神经元的低兴奋性是必要的，这是一种普遍观察到的电生理学发现。其次，我们不是像将网络的外部输入作为偏置信号那样在提示选择之间提供偏置信号，而是表明动作选择过程可以由合理水平的噪声驱动。最后，我们在皮质纹状体突触处加入了多巴胺调制学习。随着学习的进展，动作选择基于已学习的视觉提示值，并且不受学习前必需的噪声干扰。
