Afferent and efferent connections of the nucleus sphericus in the snakeThamnophis sirtalis: Convergence of olfactory and vomeronasal information in the lateral cortex and the amygdala

Abstract

This paper is an account of the afferent and efferent projections of the nucleus sphericus (NS), which is the major secondary vomeronasal structure in the brain of the snake Thamnophis sirtalis. There are four major efferent pathways from the NS: 1) a bilateral projection that courses, surrounding the accessory olfactory tract, and innervates several amygdaloid nuclei (nucleus of the accessory olfactory tract, dorsolateral amygdala, external amygdala, and ventral anterior amygdala), the rostral parts of the dorsal and lateral cortices, and the accessory olfactory bulb; 2) a bilateral projection that courses through the medial forebrain bundle and innervates the olfactostriatum (rostral and ventral striatum); 3) a commissural projection that courses through the anterior commissure and innervates mainly the contralateral NS; and 4) a meager bilateral projection to the lateral hypothalamus. On the other hand, important afferent projections to the NS arise solely in the accessory olfactory bulb, the nucleus of the accessory olfactory tract, and the contralateral NS. This pattern of connections has three important implications: first, the lateral cortex probably integrates olfactory and vomeronasal information. Second, because the NS projection to the hypothalamus is meager and does not reach the ventromedial hypothalamic nucleus, vomeronasal information from the NS is not relayed directly to that nucleus, as previously reported. Finally, a structure located in the rostral and ventral telencephalon, the olfactostriatum, stands as the major tertiary vomeronasal center in the snake brain. These three conclusions change to an important extent our previous picture of how vomeronasal information is processed in the brain of reptiles.

The vertebrate social behavior network: Evolutionary themes and variations

“…Modified from Goodson et al, 2005. Table 1 Components of the social behavior network as described for mammals (Newman, 1999) The nucleus sphericus of squamate reptiles has also been compared to the mammalian MeA based upon vomeronasal inputs, but this structure is most likely homologous to the mammalian posteromedial cortical nucleus of the amygdala (Lanuza and Halpern, 1997).…”

The Vertebrate mesolimbic reward system and social behavior network: A comparative synthesis

“…Birds: Berk andButler, 1981;Cheng et al, 1987;Wild, 1987;Berk, 1991;Balthazart and Absil, 1997;Medina and Reiner, 1997;Absil et al, 2002;Atoji et al, 2002Atoji et al, , 2006Atoji and Wild, 2004;Montagnese et al, 2008. Reptiles: Russchen andJonker, 1988;Bruce and Neary, 1995a;Smeets and Medina, 1995;Font et al, 1997;Lanuza and Halpern, 1997;Perez-Santana et al, 1997;Novejarque et al, 2004. Amphibians: Allison andWilczynski, 1991;Wilczynski and Northcutt 1983a,b;Marin et al, 1995Marin et al, , 1997aRoth and Westoff, 1999;Sanchez-Camancho et al, 2003;Endepols et al, 2005;Roden et al, 2005.…”

Proliferation, Migration, and Survival of Cells in the Telencephalon of the Ball Python, Python Regius

“…In turn, they must be stabilized by a complex muscular system. Snakes have evolved to hypertrophy these muscles, which has excluded the tympanic cavity, making the snakes' hearing ability inferior to that of other reptiles (Berman and Regal, 1967 vomeronasal system, and are considered models for determining the structure, function, and behaviors involved with vomeronasal sensing and processing (Lanuza and Halpern, 1997b).…”

“…Subsequently, Martinez-Garcia et al (1991) labeled the region as DLA in lizards, and limited the PDVR to the caudal DVR region without this additional area (Martínez-García et al, 1993). This system has been implemented in many contemporary snake and squamate brain studies (Lanuza and Halpern, 1997b;Lanuza and Halpern, 1998;Martínez-García et al, 2007). Simultaneously, several snake brain studies have continued to use the previous system (Holding et al, 2012;Krohmer et al, 2010;Krohmer et al, 2011).…”

“…The TUB links directly to the olfactory bulb, to relay and processes olfactory signals. In reptiles there has been very little study of the TUB, other than some afferent and efferent tract tracing studies (Halpern, 1976;Lanuza and Halpern, 1997a;Lanuza and Halpern, 1998). Yet the TUB has been considerably studied in mammals, and these studies have uncovered that it receives afferents from multiple sensory, storage, neuroendocrine and limbic structures (Budinger et al, 2006;Fallon, 1983;Groenewegen et al, 1987;Mick et al, 1993;Scott et al, 1980;Ubeda-Bañon et al, 2008;Vertes and Hoover, 2008).…”