Neuronal density and expression of calcium‐binding proteins across the layers of the superior colliculus in the common marmoset (Callithrix jacchus)

Abstract

The superior colliculus (SC) is a layered midbrain structure with functions that include polysensory and sensorimotor integration. Here, we describe the distribution of different immunohistochemically identified classes of neurons in the SC of adult marmoset monkeys (Callithrix jacchus). Neuronal nuclei (NeuN) staining was used to determine the overall neuronal density in the different SC layers. In addition, we studied the distribution of neurons expressing different calcium-binding proteins (calbindin [CB], parvalbumin [PV] and calretinin [CR]). Our results indicate that neuronal density in the SC decreases from superficial to deep layers. Although the neuronal density within the same layer varies little across the mediolateral axis, it tends to be lower at rostral levels, compared to caudal levels. Cells expressing different calcium-binding proteins display differential gradients of density according to depth. Both CB-and CR-expressing neurons show markedly higher densities in the stratum griseum superficiale (SGS), compared to the stratum opticum and intermediate and deep layers. However, CRexpressing neurons are twice as common as CB-expressing neurons outside the SGS.The distribution of PV-expressing cells follows a shallow density gradient from superficial to deep layers. When normalized relative to total neuronal density, the proportion of CR-expressing neurons increases between the superficial and intermediate layers, whereas that of CB-expressing neurons declines toward the deep layers. The proportion of PV-expressing neurons remains constant across layers. Our data provide layer-specific and accurate estimates of neuronal density, which may be important for the generation of biophysical models of how the primate SC transforms sensory inputs into motor signals.

Anatomy of hypothalamic and diencephalic nuclei involved in seasonal fertility regulation in ewes

“…Previous analysis indicated that these proteins have a highly phylogenetically conserved molecular structure in the brain in general and in the cerebellum in particular ( 30 , 43 , 44 ). Thus, superior colliculus and cerebellum ( Supplementary Figure 1 ) have been analyzed as positive controls, showing immunostaining properties similar to those reported for humans and other high mammals, such as the common marmoset ( 29 ). Antibodies used by us are not commercially validated for sheep.…”

“…Other hypothalamic nuclei also involved in seasonality include the supraoptic (SO), paraventricular (PVN) and arcuate (ARC) nuclei ( 27 , 28 ). With slight differences in morphology and spacial distribution, these nuclei are present in all higher mammals, including sheep ( 11 , 26 , 29 – 31 ). Full neuroanatomical and neurochemical studies of hypothalamic nuclei involved in seasonal regulation (e.g., circadian rhythms and seasonal changes in GnRH regulation) must be conducted to gain further insights into the neural basis of fertility regulation in sheep ( 24 , 32 , 33 ).…”

Retinorecipient areas in the common marmoset (Callithrix jacchus): An image-forming and non-image forming circuitry

“…The SC, also known as the optic tectum in non-mammalians, is a multimodal integrative hub for mediating sensorimotor transformations ( Sparks and Mays, 1990 ; Stein and Meredith, 1993 ; Hall and Moschovakis, 2004 ; Chong et al, 2022 ). Although higher cognitive functions are attributed to the SC ( Basso and May, 2017 ), its two main functional roles are convey retinal signals to other subcortical visual nuclei ( Kaas and Huerta, 1988 ; May, 2006 ; Basso and May, 2017 ) and integration of multimodal stimuli into motor commands for orienting movements, and to redirect attention ( Gandhi and Sparks, 2003 ; Gandhi and Katnani, 2011 ; Basso and May, 2017 ; Villalobos et al, 2018 ; Farrow et al, 2019 ).…”