Very Early Development of Nucleus Taeniae of the Amygdala

Abstract

The avian nucleus taeniae of the amygdala (TnA) corresponds to part of the mammalian medial amygdala. Like its mammalian counterpart, it has been shown to be involved in the control of social function. According to behavioral observations, such control is already necessary early in the ontogenetic development of a bird. If so, TnA should be one of the earliest differentiating brain structures of the telencephalon. Our anatomical study shows that TnA can already be delineated at posthatching day one. The volume of TnA exhibits a growth spurt between days 1 and 8 posthatch, developing at a faster rate than the entire telencephalon. Our results suggest that between days 1 and 8 the growth of neuropil exceeds the enhancement of neuron number (leading to a decrease of cell density), and an addition at the same pace of new neurons and neuropil thereafter. A plateau is reached at posthatch day 30. The development of TnA precedes that of the song control nuclei and is similar to the early growth of thalamic and telencephalic sensory areas. This adds to the idea that this structure may already be involved in social control at the time of hatching. A proximate cause of the early development of TnA might be the direct afference from the olfactory bulb.

Auditory Responses to Vocal Sounds in the Songbird Nucleus Taeniae of the Amygdala and the Adjacent Arcopallium

“…Deficits in the control of social behaviors were also observed in studies using male songbirds [Cheng et al, 1999;Ikebuchi et al, 2009]. Evidence from these hodological and behavioral studies combined with the results of immunohistochemical studies [Balthazart et al, 1992[Balthazart et al, , 1998Yamamoto et al, 2005] supports the view that the TnA corresponds to the mammalian medial amygdala [Reiner et al, 2004] and is involved in the control of both sexual and social behaviors [Cheng et al, 1999;Svec et al, 2009;Ikebuchi et al, 2009Ikebuchi et al, , 2013.…”

“…In an anatomical study that investigated the development of the TnA in zebra finches, it was shown that this nucleus can already be delineated after hatch day 1 and that its growth precedes that of the song nuclei [Ikebuchi et al, 2013]. As the authors suggested in the paper, the possibility that the TnA plays a role in promoting social interaction with a tutor should be tested because this interaction is important for facilitation of learning.…”

Genoarchitecture of the extended amygdala in zebra finch, and expression of FoxP2 in cell corridors of different genetic profile

“…However, in the Avian Brain Nomenclature Forum it became evident that only a rostromedial part of the so-called nucleus taeniae may be comparable to the medial amygdala of other vertebrates, which is primarily a subpallial structure (Reiner et al 2004a). Moreover, the nucleus taeniae identified in zebra finches (Ikebuchi et al 2013) does not appear to correspond to the subpallial nucleus taeniae recognized by the nomenclature forum as the likely homolog of the mammalian medial amygdala (Reiner et al 2004a), since such nucleus in zebra finches is located within the arcopallium. A similar situation applies to the nucleus taeniae identified in budgerigars (Roberts et al 2002).…”

“…This structure corresponds to what Reiner et al (2004a) (Avian Brain Nomenclature Forum) called the subpallial division of nucleus taeniae. Since this name is also used to refer to a pallial nucleus (Puelles et al 2007; Ikebuchi et al 2009, 2013), to avoid confusion, in the present study we adopted the nomenclature of Abellán and Medina (2009) regarding the avian medial extended amygdalar structures (see next paragraph). In particular, we are using the term subpallial medial amygdala (MeAs) or just medial amygdala (MeA) to refer to the nucleus rich in Nkx2.1, Lhx6 and Shh expressing cells, which are comparable to the pallidal and preoptic cellular components of the medial amygdala of mammals (Abellán and Medina 2009).…”

“…Studies on the neural basis of social behavior in zebra finches specifically mention the medial amygdala and the BSTM (for example, Goodson et al 2012; Kelly and Goodson 2013). However, the pallial or subpallial nature of the putative homolog of the mammalian medial amygdala in zebra finch (the so-called nucleus taeniae, Ikebuchi et al 2013) is unclear. This is an important issue, since the medial amygdala in other vertebrates (including chicken) is primarily a subpallial nucleus rich in neurons of pallidal and preoptic origins, although it also includes some minor subpopulations of immigrant neurons coming from the ventral pallium or from the hypothalamus (García-López et al 2008; Abellán and Medina 2009; Bupesh et al 2011a).…”