The Pulvinar Thalamic Nucleus of Non-Human Primates: Architectonic and Functional Subdivisions by Ricardo Gattass Juliana G.M. Soares & Bruss Lima

Author:Ricardo Gattass, Juliana G.M. Soares & Bruss Lima
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Investigating the calbindin immunoreactivity in the macaque monkey pulvinar, Adams et al. (2000) extended the original cytoarchitectonic subdivisions previously described by Olszewski (1952) and offered new insight into pulvinar delimitation and connectivity pattern. PM was easily distinguished from PL by its distribution pattern of both large and small calbindin-containing neurons and by its neuropil disposition and staining. In addition, calbindin staining suggested further partitioning of PI that was not evident in previous studies using only the Nissl stain. The original PI could thereby be further subdivided into PIP, PIM, PICM, and PICL. Both the PIP and PIC zones displayed the strongest calbindin immunoreactivity. The PICL zone was moderately reactive for calbindin staining, while PIM was almost devoid of calbindin immunoreactivity. The border between P1 and P2, and the lateral border of P3 with P1 and P2, could be defined using calbindin immunoreactivity. Nissl staining, while being able to identify these borders, revealed an otherwise fairly homogenous staining pattern, which was only interrupted by the brachium of the SC.

The neurons that project to area V1 in New and Old World monkeys were found in the dorsal portion of PICL, and they overlapped the pulvinar field projecting to area V2 in all animals studied (Stepniewska and Kaas 1997). Additionally, the pulvinar projection zones to areas V1 and V2 fell within the visual field maps of P1 and P2. There was another projection zone to area V2 that was found in P3 of all monkeys studied. The neurons projecting to area MT were found in the ventral part of PM, scattered throughout PL, and in the PIL, PIM, PICM, and PICL subdivisions. Therefore, in accordance with Ungerleider et al. (1984), the strongest projections to MT originated in P3. Note that the labeled neurons seen in the ventral part of PM could have been the result of an extravasation of the tracer injections into neighboring area FST. The neurons projecting to area V4 were observed in PICL, PICM, and PIP and occupied portions of all three visual field maps (P1, P3, and P4).

Figure 6.2 offers an integrated perspective of pulvinar partitioning based on calbindin immunostaining and the connectivity strength of each of the corresponding pulvinar subdivisions with visual areas V1, V2, V4, and MT. Note the PI partitioning into posterior (PIP), medial (PIM)), central medial (PICM), and central lateral (PICL) regions. The P1 field, as described by Ungerleider et al. (1983), includes PICL and the ventromedial portion of PL (i.e., PLVM). The P2 field corresponds to the ventrolateral portion of PL (i.e., PLVL), while the P3 field corresponds to PIP, PIM, and PICM. Projection fields to areas V1 and V2 were found to be overlapping in P1 and P2, but the projections from P2 to V2 were found to be denser than those to V1. V2 also received light projections from PICM and, less reliably, from PIM. Pulvinar projections to V4 and MT were more abundant than projections to V1 and V2. Neurons projecting to V4 were observed in P1, P2, and in subdivisions PIP and PICM of P3.

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