Abstract
Birds are extremely interesting animals for studying the neurobiological basis of cognition and its evolution. They include species that are highly social and show high cognitive capabilities. Moreover, birds rely more on visual and auditory cues than on olfaction for social behavior and cognition, just like primates. In primates, there are two major brain networks associated to sociality: (1) one related to perception and decision-making, involving the pallial amygdala (with the basolateral complex as a major component), the temporal and temporoparietal neocortex, and the orbitofrontal cortex; (2) another one related to affiliation, including the medial extended amygdala, the ventromedial prefrontal and anterior cingulate cortices, the ventromedial striatum (largely nucleus accumbens), and the ventromedial hypothalamus. In this account, we used an evolutionary developmental neurobiology approach, in combination with published comparative connectivity and functional data, to identify areas and functional networks in the sauropsidian brain comparable to those of mammals that are related to decision-making and affiliation. Both in mammals and sauropsids, there is an important interaction between these networks by way of cross projections between areas of both systems.
Highlights
In primates, several studies have shown a correlation between social network size and the volumes of specific parts of the telencephalic pallium, including the orbitofrontal cortex, the cortical and basolateral amygdala, the temporo-parietal cortical junction, and the superior temporal sulcus (Lewis and Barton, 2006; Powell et al, 2010, 2012; Bickart et al, 2011; Kanai et al, 2011)
The network related to social perception involves the “ventrolateral amygdala”, the fusiform gyrus and other temporal neocortical areas, and the orbitofrontal cortex; the network related to social affiliation involves the medial amygdala, the ventromedial prefrontal cortex and adjacent subgenual and anterior cingulate cortical areas, the ventromedial striatum, and the ventromedial hypothalamus (Bickart et al, 2012)
For inter-species brain comparisons to make sense, it is mandatory to first unravel the brain building plan (Bauplan or morphoplan), which is shared by different vertebrates. Developmental studies, those on combinatorial expression patterns of early regulatory genes in relation to the topological framework of the neural tube, have become extremely useful to unravel the brain morphoplan, with its basic divisions comparable across vertebrates (Nieuwenhuys and Puelles, 2016). The conclusions of this type of approach support that a large lateroventral part of the avian and reptilian pallium derives from pallial embryonic divisions that gives rise to the pallial amygdala and other areas of the so-called piriform lobe in mammals (Puelles et al, 2000, 2017; Medina et al, 2011, 2017a; Abellán et al, 2013; Desfilis et al, 2018), a proposal supported by results of fate mapping (Hirata et al, 2009; Soma et al, 2009; Waclaw et al, 2010; Bupesh et al, 2011; Puelles et al, 2016a; García-Moreno et al, 2018; Rueda-Alaña et al, 2018), tract-tracing studies (Bruce and Neary, 1995; Martínez-García et al, 2007), and more recently, by single-cell transcriptome (Tosches et al, 2018)
Summary
Several studies have shown a correlation between social network size and the volumes of specific parts of the telencephalic pallium, including the orbitofrontal cortex, the cortical and basolateral amygdala, the temporo-parietal cortical junction, and the superior temporal sulcus (Lewis and Barton, 2006; Powell et al, 2010, 2012; Bickart et al, 2011; Kanai et al, 2011). Developmental studies, those on combinatorial expression patterns of early regulatory genes in relation to the topological framework of the neural tube, have become extremely useful to unravel the brain morphoplan, with its basic divisions comparable across vertebrates (Nieuwenhuys and Puelles, 2016) The conclusions of this type of approach support that a large lateroventral part of the avian and reptilian pallium (called the dorsal ventricular ridge) derives from pallial embryonic divisions that gives rise to the pallial amygdala and other areas of the so-called piriform lobe in mammals (Puelles et al, 2000, 2017; Medina et al, 2011, 2017a; Abellán et al, 2013; Desfilis et al, 2018), a proposal supported by results of fate mapping (Hirata et al, 2009; Soma et al, 2009; Waclaw et al, 2010; Bupesh et al, 2011; Puelles et al, 2016a; García-Moreno et al, 2018; Rueda-Alaña et al, 2018), tract-tracing studies (Bruce and Neary, 1995; Martínez-García et al, 2007), and more recently, by single-cell transcriptome (Tosches et al, 2018). Based on cell lineage tracing and gene expression patterns, the VP derivatives do not include the whole olfactory bulbs, but only part of them (as discussed by Desfilis et al, 2018)
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