In 1998, Jones suggested a classification of thalamocortical projections into core and matrix divisions (Jones, 1998). In this classification, core projections are specific, topographical, innervate middle cortical layers, and serve to transmit specific information to the cortex for further analysis; matrix projections, in contrast, are diffuse, much less topographic, innervate upper layers, especially Layer 1, and serve a more global, modulatory function, such as affecting levels of arousal. This classification has proven especially influential in studies of thalamocortical relationships. Whereas it may be the case that a clear subset of thalamocortical connections fit the core motif, since they are specific, topographic, and innervate middle layers, we argue that there is no clear evidence for any single class that encompasses the remainder of thalamocortical connections as is claimed for matrix. Instead, there is great morphological variation in connections made by thalamocortical projections fitting neither a core nor matrix classification. We thus conclude that the core/matrix classification should be abandoned, because its application is not helpful in providing insights into thalamocortical interactions and can even be misleading. As one example of the latter, recent suggestions indicate that core projections are equivalent to first-order thalamic relays (i.e., those that relay subcortical information to the cortex) and matrix to higher-order relays (i.e., those that relay information from one cortical area to another), but available evidence does not support this relationship. All of this points to a need to replace the core/matrix grouping with a more complete classification of thalamocortical projections.

1998 年，琼斯建议将丘脑皮质​​投射分为核心和矩阵划分（琼斯，1998 ）。在这种分类中，核心投射是特定的、地形的、支配中皮层的，并用于将特定信息传输到皮层以进行进一步分析；相比之下，矩阵投影是分散的，更不用说地形了，它支配上层，尤其是第一层，并提供更全局的调节功能，例如影响唤醒水平。事实证明，这种分类在丘脑皮质关系的研究中特别有影响力。尽管丘脑皮质连接的一个明确子集可能符合核心主题，因为它们是特定的、地形的和神经支配的中间层，但我们认为没有明确的证据表明任何单一类别包含丘脑皮质连接的其余部分被要求为矩阵。相反，丘脑皮质投影所形成的连接存在很大的形态变化，既不适合核心分类，也不适合矩阵分类。因此，我们得出的结论是，核心/基质分类应该被放弃，因为它的应用无助于提供丘脑皮质相互作用的见解，甚至可能产生误导。作为后者的一个例子，最近的建议表明，核心投射相当于一阶丘脑中继（即，将皮层下信息中继到皮层的中继）和矩阵到高阶中继（即，从一个皮质中继信息的中继）。区域到另一个区域），但现有证据并不支持这种关系。所有这些都表明需要用更完整的丘脑皮质投射分类来取代核心/矩阵分组。