Avian brains and a new understanding of vertebrate brain evolution

Abstract

We believe that names have a powerful influence on the experiments we do and the way in which we think. For this reason, and in the light of new evidence about the function and evolution of the vertebrate brain, an international consortium of neuroscientists has reconsidered the traditional, 100-year-old terminology that is used to describe the avian cerebrum. Our current understanding of the avian brain -in particular the neocortex-like cognitive functions of the avian pallium -requires a new terminology that better reflects these functions and the homologies between avian and mammalian brains.One hundred years ago, Edinger, the father of comparative neuroanatomy, formulated a unified theory of brain evolution that formed the basis of a nomenclature that has been used to define the cerebral subdivisions of all vertebrates 1 . This resulted in terms and associated concepts such as palaeostriatum, archistriatum, neostriatum and neocortex that are still in common use. According to this theory, the avian cerebrum is almost entirely composed of basal ganglia, the basal ganglia is involved in only instinctive behaviour, and the malleable behaviour that is thought to typify mammals exclusively requires the so-called neocortex. However, towards the end of the twentieth century, there accumulated a wealth of evidence that these viewpoints were incorrect. The avian cerebrum has a large pallial territory that performs functions similar to those of the mammalian cortex. Although the avian pallium is nuclear, and the mammalian cortex is laminar in organization, the avian pallium supports cognitive abilities similar to, and for some species more advanced than, those of many mammals. To eliminate these misconceptions, an international forum of neuroscientists (BOX 1) has, for the first time in 100 years, developed new terminology that more accurately reflects our current understanding of the avian cerebrum and its homologies with mammals. This change in terminology is part of a new understanding of vertebrate brain evolution.In this article, we summarize the traditional view of telencephalic evolution before reviewing more recent findings and insights. We then present the new nomenclature that has been Correspondence to Erich Jarvis at the

From sauropsids to mammals and back: New approaches to comparative cortical development

“…Diversification of the adult brain in gene expression and morphology across vertebrate phylogeny makes comparisons difficult (Aboitiz and Montiel, 2007; Wang et al, 2011a; Belgard and Montiel, 2013). The cerebral hemispheres of vertebrates show enormous diversity, having differences in size and complexity distinct for each clade (Jarvis et al, 2005, 2013; Aboitiz and Montiel, 2007). Some remarkable examples of brain diversification in vertebrates can be found in fish, where cartilaginous fish have an expanded central nucleus (Aboitiz and Montiel, 2007), whereas teleosts have an everted brain (Butler and Hodos, 2005).…”

Increased juvenile predation is not associated with evolved differences in adult brain size in Trinidadian killifish (Rivulus hartii)

“…It has long been known that vertebrates exhibit extensive variation in brain size (Bauchot, Bauchot, Platel, & Ridet, 1977; Crile & Quiring, 1940; Jarvis et al., 2005; Mink, Blumenschine, & Adams, 1981; Striedter, 2005; Taylor & van Schaik, 2007). There are clear fitness benefits associated with a larger brain as brain size is positively correlated with increased intelligence, cognition, learning capability, population persistence, and decreased susceptibility to predation (Sol & Lefebvre, 2000; Tebbich & Bshary, 2004; Shultz & Dunbar, 2006a; Sol, Szekely, Liker, & Lefebvre, 2007; Sol, Bacher, Reader, & Lefebvre, 2008; Overington, Morand‐Ferron, Boogert, & Lefebvre, 2009; Barrickman, Bastian, Isler, & van Schaik, 2008; Amiel, Tingley, & Shine, 2011; Reader, Hager, & Laland, 2011; Kotrschal et al., 2013b; MacLean et al., 2014; Kotrschal et al., 2015a; Kotrschal, Corral‐Lopez, Amcoff, & Kolm, 2015b; Benson‐Amram, Dantzer, Stricker, Swanson, & Holekamp, 2016; but also see Drake, 2007).…”

Learning generalization in problem solving by a blue-fronted parrot (Amazona aestiva)

“…This hypothesis comes from primatology (Jolly 1966;Humphrey 1976;Byrne and Whiten 1988) and has been extended to other taxonomic groups (de Waal and Tyack 2003); if so, we should expect Psittacids to be particularly well-endowed with cognitive abilities, since they live in large groups and are monogamous (Emery et al 2007). Moreover, they have a relatively large pallial area in the brain, which, in birds, is responsible for complex cognitive processes (analogous to the mammalian neocortex; Jarvis et al 2005). Wright (1996) and Sauders (1983) suggested that parrots have the ability to recognize individuals (group members or mates) by their vocalizations.…”