Limbic Nuclei of Thalamus and Connections of Limbic Cortex

Abstract

Introduction Comparative studies of the thalami of various mammals,² including marsupials,⁵ the rabbit,^28,61,80 rodents,^25,29,33 the sheep,⁶² carnivores,^30,60,79 and primates,^10,15,72-75 demonstrate a progressive phylogenetic enlargement and differentiation of nucleus medialis dorsalis (MD), in parallel with the development and elaboration of the frontal lobes (ie, opercularization of insula). In man, MD is the largest member of the internal segment of the dorsal thalamus; the anterior, lateral, and inferior borders of the nucleus are clearly delineated by the internal medullary lamina in myelin-stained sections and are visible even in unstained slices of the fresh brain. The precise cytoarchitectonic differentiation of MD from neighboring nuclei—the midline and intralaminar nuclei and the medial pulvinar—is difficult, however, at several points.^54,65 A number of authors (Clark,¹⁰ Walker,^72-75 Sheps,⁶⁵ Toncray and Krieg,⁶⁹ Olszewski,⁵⁴ Dekaban¹⁸) have recognized in primates two or three and sometimes four