Delineation of thalamic nuclei immunoreactive for calcium-binding proteins in and around the posterior pole of the ventral posterior complex

An atlas of serial sections stained alternately for one of the three calcium-binding proteins, calbindin, calretinin or parvalbumin, or for markers that demarcate borders of thalamic nuclei in and around the posterior pole of the ventral posterior thalamic nucleus of a macaque monkey is presented. The concentrated focal zone of calbindin-immunoreactive fiber ramifications considered by others to form a specific pain and temperature relay nucleus is shown to be located entirely within the confines of the ventral posterior medial (VPM) nucleus. It contains a large population of calbindin-immunoreactive cells and overlaps a region of dense cell and fiber immunoreactivity for parvalbumin. In other parts of the ventral posterior complex, calbindin and parvalbumin immunoreactivity is complementary rather than co-extensive. It is unlikely that the zone of intense calbindin immunoreactivity in VPM forms the only thalamic relay for noxious thermal and mechanical inputs to the cerebral cortex.