Cerebral representations are encoded as patterns of activity involving billions of neurons. Parallel distributed processing (PDP) across these neuronal populations provides the basis for a number of emergent properties: 1) processing occurs and knowledge (long term memories) is stored (as synaptic connection strengths) in exactly the same networks; 2) networks have the capacity for setting into stable attractor states corresponding to concepts, symbols, implicit rules, or data transformations; 3) networks provide the scaffold for the acquisition of knowledge but knowledge is acquired through experience; 4) PDP networks are adept at incorporating the statistical regularities of experience as well as frequency and age of acquisition effects; 5) networks enable content-addressable memory; 6) because knowledge is distributed throughout networks, they exhibit the property of graceful degradation; 7) networks intrinsically provide the capacity for inference. This paper details the features of the basal ganglia and thalamic systems (recurrent and distributed connectivity) that support PDP. The PDP lens and an understanding of the attractor trench dynamics of the basal ganglia provide a natural explanation for the peculiar dysfunctions of Parkinson’s disease and the mechanisms by which dopamine deficiency is causal. The PDP lens, coupled with the fact that the basal ganglia of humans bears strong homology to the basal ganglia of lampreys and the central complex of arthropods, reveals that the fundamental function of the basal ganglia is computational and involves the reduction of the vast dimensionality of a complex multi-dimensional array of sensorimotor input into the optimal choice from a small repertoire of behavioral options — the essence of reactive intention (automatic responses to sensory input). There is strong evidence that the sensorimotor basal ganglia make no contributions to cognitive or motor function in humans but can cause serious dysfunction when pathological. It appears that humans, through the course of evolution, have developed cortical capacities (working memory and volitional and reactive attention) for managing sensory input, however complex, that obviate the need for the basal ganglia. The functions of the dorsal tier thalamus, however, even viewed with an understanding of the properties of population encoded representations, remain somewhat more obscure. Possibilities include the enabling of attractor state constellations that optimize function by taking advantage of simultaneous input from multiple cortical areas; selective engagement of cortical representations; and support of the gamma frequency synchrony that enables binding of the multiple network representations that comprise a full concept representation.

大脑表征被编码为涉及数十亿神经元的活动模式。跨这些神经元群的并行分布式处理 (PDP) 为许多紧急属性提供了基础：1) 处理发生并且知识（长期记忆）被存储（作为突触连接强度）在完全相同的网络中；2) 网络具有将概念、符号、隐含规则或数据变换对应的稳定吸引子状态设置的能力；3）网络为获取知识提供了支架，但知识是通过经验获取的；4）PDP网络善于结合经验的统计规律以及获取效应的频率和年龄；5) 网络支持内容可寻址内存；6）因为知识分布在整个网络中，它们表现出优雅退化的特性；7) 网络本质上提供推理能力。本文详细介绍了支持 PDP 的基底神经节和丘脑系统（循环和分布式连接）的特征。PDP 晶状体和对基底神经节吸引沟动力学的理解为帕金森病的特殊功能障碍和多巴胺缺乏的致病机制提供了自然的解释。PDP透镜，再加上人类的基底神经节与七鳃鳗的基底神经节和节肢动物的中央复合体具有很强的同源性，揭示了基底神经节的基本功能是计算，涉及将复杂的多维感觉运动输入阵列的大量维度减少到从一小部分行为选项中的最佳选择——反应性意图的本质（对感官输入）。有强有力的证据表明，感觉运动基底节对人类的认知或运动功能没有贡献，但在病理时会导致严重的功能障碍。人类似乎在进化过程中已经发展出皮层能力（工作记忆和意志和反应性注意力）来管理感觉输入，无论多么复杂，都不需要基底神经节。然而，背侧丘脑的功能，即使理解了人口编码表示的特性，仍然有些模糊。可能性包括启用吸引子状态星座，通过利用来自多个皮层区域的同时输入来优化功能；皮层表征的选择性参与；并且支持伽马频率同步，使得能够绑定构成完整概念表示的多个网络表示。