Humphries M D, Gurney K, Prescott T J
Adaptive Behaviour Research Group, Department of Psychology, University of Sheffield, Sheffield S10 2TP, UK.
Philos Trans R Soc Lond B Biol Sci. 2007 Sep 29;362(1485):1627-39. doi: 10.1098/rstb.2007.2057.
The search for the neural substrate of vertebrate action selection has focused on structures in the forebrain and midbrain, and particularly on the group of sub-cortical nuclei known as the basal ganglia. Yet, the behavioural repertoire of decerebrate and neonatal animals suggests the existence of a relatively self-contained neural substrate for action selection in the brainstem. We propose that the medial reticular formation (mRF) is the substrate's main component and review evidence showing that the mRF's inputs, outputs and intrinsic organization are consistent with the requirements of an action-selection system. The internal architecture of the mRF is composed of interconnected neuron clusters. We present an anatomical model which suggests that the mRF's intrinsic circuitry constitutes a small-world network and extend this result to show that it may have evolved to reduce axonal wiring. Potential configurations of action representation within the internal circuitry of the mRF are then assessed by computational modelling. We present new results demonstrating that each cluster's output is most likely to represent activation of a component action; thus, coactivation of a set of these clusters would lead to the coordinated behavioural response observed in the animal. Finally, we consider the potential integration of the basal ganglia and mRF substrates for selection and suggest that they may collectively form a layered/hierarchical control system.
对脊椎动物动作选择神经基质的研究主要集中在前脑和中脑结构上，尤其是被称为基底神经节的一组皮质下核团。然而，去大脑动物和新生动物的行为表现表明，脑干中存在一个相对独立的动作选择神经基质。我们认为内侧网状结构（mRF）是该基质的主要组成部分，并回顾了相关证据，这些证据表明mRF的输入、输出和内在组织与动作选择系统的要求相一致。mRF的内部结构由相互连接的神经元簇组成。我们提出了一个解剖模型，该模型表明mRF的内在电路构成了一个小世界网络，并扩展了这一结果以表明它可能已经进化以减少轴突布线。然后通过计算建模评估mRF内部电路中动作表征的潜在配置。我们展示了新的结果，表明每个簇的输出最有可能代表一个组成动作的激活；因此，一组这些簇的共同激活将导致在动物身上观察到的协调行为反应。最后，我们考虑基底神经节和mRF基质在选择方面的潜在整合，并表明它们可能共同形成一个分层/分级控制系统。
