Neurochemical and connectional organization of the dorsal pulvinar complex in monkeys

To investigate the organization of the dorsal pulvinar complex, patterns of neurochemical staining were correlated with cortico-pulvinar connections in macaques (Macaca mulatta). Three major neurochemical subdivisions of the dorsal pulvinar were identified by acetylcholinesterase (AChE) histochemistry, as well as immunostaining for calbindin-D(28K) and parvalbumin. The dorsal lateral pulvinar nucleus (PLd) was defined on histochemical criteria as a distinct AChE- and parvalbumin-dense, calbindin-poor wedge that was found to continue caudally along the dorsolateral edge of the pulvinar to within 1 mm of its caudal pole. The ventromedial border of neurochemical PLd with the rest of the dorsal pulvinar, termed the medial pulvinar (PM), was sharply defined. Overall, PM was lighter than PLd for AChE and parvalbumin and displayed lateral (PMl) and medial (PMm) histochemical divisions. PMm contained a central "oval" (PMm-c) that stained darker for AChE and parvalbumin than the surrounding region. The neurochemically defined PLd was labeled by tracer injections in the inferior parietal lobule (IPL) and dorsolateral prefrontal cortex but not the superior temporal gyrus (STG). Label within PMl was found after prefrontal and IPL and, to a lesser extent, after STG injections. The PMm was labeled after injections of the IPL and STG, but only sparsely following prefrontal injections. The histochemically distinct subregion or module of PMm, PMm-c, was labeled only by STG injections. Overlapping labeling was found in dorsal pulvinar divisions PMl and PLd following paired IPL/prefrontal, but not IPL/STG or these particular STG/prefrontal, injections. Thus, PLd may be a visuospatially related region whereas PM appears to contain several types of territories, some related to visual or auditory inputs, and others that receive directly converging input from posterior parietal and prefrontal cortex and may participate in a distributed cortical network concerned with visuospatial functions.