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The Functional CNS Model - Rat is one of three hierarchical models representing the internal organization of the central nervous system (CNS). The others are the Classical Model and the Developmental Model. Of the three, the Functional CNS Model - Rat is the most useful for addressing the fundamental question of neuroscientific research, namely, the relation between neuroanatomical structure and function.
In the Functional Model structures are grouped based on information drawn from all neuroscientific disciplines. They are not grouped as in the Developmental Model, primarily by origin in the embryonic brain, nor as in the Classical Model, primarily on the basis of proximity as observed by dissection and histological stains for Nissl substance and myelin. In the Functional Model they are grouped additionally by other functionally important features, such as connections, neurochemical characteristics, and role in physiogical and behavioral processes. While the Functional Model was developed primarily for an atlas of the rat brain ( Swanson-2004 ), the hierarchical organization of structures is for the most part applicable to the human, macaque, mouse and other mammalian brains as well.
Structures at lower levels of the Functional CNS hierarchy are largely the same as in the Classical and Developmental Models, i.e., they were originally identified by stains for gray matter (Nissl substance) and white matter (myelin). At the next higher level they are grouped into basic connectional and functional systems of the CNS, such as the subcortical sensory systems, the subcortical motor system and the behavioral state system. At the highest levels CNS structures are grouped on the basis of dissection and embryologic precursors into cerebrum ( cerebral cortex and cerebral nuclei ), cerebellum, and cerebrospinal trunk.
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