Thalamic connections of the dorsomedial visual area in primates

Abstract

The dorsomedial visual area (DM) of owl monkeys is a cortical area that has been described recently in a range of primate species. To study the thalamic connections of this area, injections of several distinguishable neuroanatomical tracers were placed into DM in galagos, owl monkeys, squirrel monkeys, and macaque monkeys. The distribution of label was remarkably consistent across these diverse primate species. Labeled connections were densest within the pulvinar complex. Both the lateral and inferior divisions of the pulvinar, but not the medial division, had connections with DM. Within the inferior pulvinar of monkeys, central lateral and central medial nuclei had dense connections, and the medial and posterior nuclei had sparse connections with DM. Sparser connections were revealed in the lateral geniculate nucleus and the nucleus limitans. Anterograde label was also found in the superior colliculus. The consistencies in the pattern of subcortical projections across prosimian primates, New World monkeys, and Old World monkeys support the concept that DM is a visual area common to all primates. In addition, these results provide further evidence for proposed subdivisions of the inferior pulvinar.

Projections of the superior colliculus to the pulvinar in prosimian galagos (Otolemur garnettii) and VGLUT2 staining of the visual pulvinar

“…Histological staining procedures within the pulvinar complex of galagos have proven to be less robust and therefore less helpful in delineating subdivisions (Beck and Kaas, 1998; Wong et al, 2009) than they have been for anthropoid primates (Cusick et al, 1993; Gutierrez et al, 1995; Stepniewska and Kaas, 1997; Adams et al, 2000; Jones, 2007), making the assignment of homologues between prosimians and anthropoids difficult (Beck and Kaas, 1998; Wong et al, 2009). …”

“…Much less is known about the divisions of the pulvinar of galagos, mainly because of the lack of architectonic markers that distinguish between divisions (Beck and Kaas, 1998; Wong et al, 2009). Therefore, it has been difficult to identify homologous pulvinar structures between galagos and other primates, and between primates and rodents (see Lyon et al, 2003 for review).…”

Pulvinar contributions to the dorsal and ventral streams of visual processing in primates

“…To some extent, inputs from V1 and V2 suggest that V3 resembles V1 and V2 in having a role in both streams. While the pulvinar and cortical connections of V3 are not fully established because it has been difficult to define the borders of V3, injections in caudal DM (Beck and Kaas, 1998b), in cortex next to V2 that now appears to be largely V3, labeled large numbers of neurons in PLvl and PIcl, although some labeled neurons were in PIcm and PIp. Conversely, the results of other studies suggest a greater contribution of projections to V3d from the medial nuclei and the lateral shell of the inferior pulvinar (Shipp, 2001).…”

Peripheral variability and central constancy in mammalian visual system evolution

“…Using modern physiological and anatomical methods, primary and secondary visual, somatosensory and auditory cortical areas have been mapped in diverse species, including primates, rodents, various marsupials and the monotremes. These studies can help clarify cross-species allometric trends, effects of lineage and effects of niches (Luethke et al 1988(Luethke et al , 1989Krubitzer & Kaas 1990, 1993Felleman & Van Essen 1991;Krubitzer et al , 1997Preuss et al 1993;Krubitzer 1995Krubitzer , 1998Beck et al 1996;Preuss & Kaas 1996;Van Essen & Drury 1997;Beck & Kaas 1998;Lyon et al 1998;Catania et al 1999;Huffman et al 1999;Rosa 1999;Rosa et al 1999;Slutsky et al 2000). This report attempts to systematically examine neocortical organization in 30 mammalian species, using the method of independent contrasts to control for lineage effects (Harvey & Pagel 1991;Purvis & Rambaut 1995).…”