Efferents and Centrifugal Afferents of the Main and Accessory Olfactory Bulbs in the Snake <i>Thamnophis sirtalis</i>

Abstract

This study reinvestigates the efferent projections of the main and accessory olfactory bulbs and describes for the first time the centrifugal projections to the main and accessory olfactory bulbs in the snake Thamnophis sirtalis, using the intraaxonal transport of the anterograde and retrograde tracer biotinylated dextran amine and the retrograde tracer horseradish peroxidase. The olfactory projection consists of three tracts: the lateral olfactory tract, which projects bilaterally to the lateral cortex and the rostral amygdala, crossing the midline through the stria medullaris-habenular commissure system; the intermediate olfactory tract, which projects ipsilaterally to the olfactory tubercle and contributes to the contralateral projection; and the medial olfactory tract, which projects ipsilaterally to the dorsomedial retrobulbar formation. The vomeronasal projection is formed by a single tract, the accessory olfactory tract, that projects ipsilaterally to the nucleus of the accessory olfactory tract, the medial amygdala and the nucleus sphericus. The centrifugal projections to the main and accessory olfactory bulb are composed of two components: one that arises in areas that receive the olfactory or vomeronasal input (neurons in the olfactory tubercle, retrobulbar formation and lateral cortex project to the main olfactory bulb; and neurons in the nucleus of the accessory olfactory tract, the medial amygdala and the nucleus sphericus project to the accessory olfactory bulb), and another that arises in areas not directly implicated in processing the chemosensory information (the nucleus of the diagonal band of Broca and the dorsal cortex). These data allow the recognition of the general pattern of organization of the reptilian olfactory and vomeronasal systems.

Diverse Systems for Pheromone Perception: Multiple Receptor Families in Two Olfactory Systems

“…The vomeronasal neurons of garter snakes project to the AOB, and then project mainly to the medial amygdala and nucleus sphericus (Halpern and Martinez-Marcos, 2003); the nucleus sphericus also projects to the medial amygdala and the lateral cortex (Halpern and Martinez-Marcos, 2003). As the medial amygdala and the lateral cortex are the vomeronasal recipient and main olfactory recipient structures, respectively, garter snakes possess two distinct pathways from the AOB: one for recognizing odors and another for recognizing pheromones (Lanuza and Halpern, 1998). Although nonvolatile female and male sex pheromones were identified in garter snakes (Mason et al, 1989), the reptile pheromone receptors have not yet been reported.…”

The vertebrate social behavior network: Evolutionary themes and variations

“…These include a vocally-active tegmental field that lies lateral to the PAG and medial to the auditory torus/ inferior colliculus (Phillips et al, 1972;Kennedy, 1975;Jürgens, 1994;Goodson and Bass, 2002) in all classes except Amphibia, in which a comparable vocal site is located at isthmal levels (Wetzel et al, 1985). Other selected references : Northcutt, 1981;Bruce and Neary, 1995;Balthazart et al, 1996;Panzica et al, 1996;Wong, 1997;Coolen and Wood, 1998;Lanuza and Halpern, 1998;Nieuwenhuys et al, 1998;Cheng et al, 1999;Goodson and Bass, 2000c;Dong et al, 2001;Petrovich et al, 2001;Goodson et al, 2003;Moreno and Gonzalez, 2003;Dong and Swanson, 2004;Goodson et al, 2004a;Rink and Wullimann, 2004;…”

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

“…In this area the lateral ventricle separates the nucleus sphericus (NS) completely from the cortex. Due to the importance of pheromone perception, the NS is very well developed in snakes and occupies almost the entire caudal half of the subcortical telencephalon (Halpern, 1980;Lanuza and Halpern, 1998;Schwenk, 1993).…”

“…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).…”