Efferent connections of septal nuclei of the domestic chick (Gallus domesticus): An anterograde pathway tracing study with a bearing on functional circuits

Abstract

Small iontophoretic injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin were placed in different subregions of the septum of domestic chicks. The main targets of septal projections comprised the ipsi- and contralateral septal nuclei, including the nucleus of the diagonal band, basal ganglia, including the ventral paleostriatum, lobus parolfactorius, nucleus accumbens, and olfactory tubercle, archistriatum, piriform cortex, and anterior neostriatum. Further diencephalic and mesencephalic septal projections were observed in the ipsilateral preoptic region, hypothalamus (the main regions of afferentation comprising the lateral hypothalamic nuclei, ventromedial, paraventricular and periventricular nuclei, and the mammillary region), dorsal thalamus, medial habenular and subhabenular nuclei, midbrain central gray, and ventral tegmental area. Contralateral projections were also encountered in the septal nuclei, ventral paleostriatum, periventricular and anteromedial hypothalamic nuclei, suprachiasmatic nucleus, and the lateral hypothalamic area. Avian septal efferents are largely similar to those of mammals, the main differences being a relatively modest hippocampal projection arising mainly from the nucleus of the diagonal band (as confirmed by a specific experiment with the retrograde pathway tracer True blue), the lack of interpeduncular projection, and a greater contingent of amygdalar efferents arising from the lateral septum rather than the nucleus of the diagonal band. This pattern of connectivity is likely to reflect an important role of the avian septal nuclei in the coordination of limbic circuits and the integration of a wide variety of information sources modulating the appropriate behavioral responses: attention and arousal level, memory formation, hormonally mediated behaviors, and their affective components (such as ingestive, reproductive, and parental behaviors), social interaction, locomotor modulation, and circadian rhythm.

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

“…There are dense dopaminergic fibers in this region (Bailhache and Balthazart, 1993), similar to mammals. This region is neurochemically very similar to the mammalian LS (Caffe et al, 1987;Montagnese et al, 2004; discussed in detail in Goodson et al, 2004).…”

Recent advances in behavioral neuroendocrinology: Insights from studies on birds

“…In birds, recent tracing studies demonstrate reciprocal connectivity throughout the same suite of steroid-sensitive areas (identically named, with the exception of the avian medial amygdala, which is known as the nucleus taeniae) Briganti et al, 1996;Balthazart and Absil, 1997;Cheng et al, 1999;Montagnese et al, 2004;Riters and Alger, 2004), and a variety of functional data are now available regarding their roles in overt aggression, agonistic communication, appetitive and consummatory sexual behavior, parental behavior, and nonsexual affiliation Thompson et al, 1998;Goodson et al, 1999Goodson et al, , 2005Riters and Ball, 1999;Absil et al, 2002;Goodson and Evans, 2004;Ruscio and Adkins-Regan, 2004;Charlier et al, 2005). These functional studies have established extensive similarities with other taxa.…”

“…All forebrain components of the social behavior network project to the midbrain central gray, as do preoptic aromatase neurons (Cheng et al, 1999;Absil et al, 2001;Montagnese et al, 2004;Riters and Alger, 2004). The central gray in turn provides direct input to the telencephalic song system (i.e., monosynaptic projections are observed for HVC and RA) (Appeltants et al, 2000).…”

The vertebrate social behavior network: Evolutionary themes and variations

“…2B-C) The social behavior network in birds A wide variety of data have been collected on the neuroendocrine systems of birds, and the avian literature is growing rapidly (Goodson et al, submitted-b). On the whole, the social behavior network in birds exhibits extensive similarities with the mammalian network in its connections, histochemistry, and locations of sex steroid receptors (e.g., Watson and AdkinsRegan, 1989;Balthazart et al, 1994;Balthazart et al, 1996;Briganti et al, 1996;Aste et al, 1998;Cheng et al, 1999;Atoji and Wild, 2004;Goodson et al, 2004a;Montagnese et al, 2004). The pattern of IEG induction that is observed in birds following agonistic interactions is also comparable to that observed in mammals, as are IEG responses to appetitive and consummatory sexual interactions (Kollack-Walker and Newman, 1995;Coolen et al, 1996Coolen et al, , 1997Kollack-Walker et al, 1997;Meddle et al, 1997Meddle et al, , 1999Delville et al, 2000;Tlemcani et al, 2000;Maney and Ball, 2003;Davis and Marler, 2004;Goodson and Evans, 2004;Riters et al, 2004; Goodson et al, submitted-a),.…”