Brain evolution by brain pathway duplication

“Other hypotheses posit that existing genes are modified, including changes in coding sequence, cis-regulatory motifs [16,17] or new alternative mRNA splice variants [18–21], a process known as subfunctionalization [12–14].”

“One of the duplicated genes may then acquire a mutation in coding or regulatory sequences, which enables it to acquire a new function that then undergoes selection, a process known as neofunctionalization [12–15].”

“With the recent availability of genomes across the avian [93,177,178] and eventually primate [179,180] family trees, it becomes possible to discover candidate genes.”

“Based on these and other findings, it is generally proposed that the direct CM system of M1 is a recently evolved brain structure that conferred evolutionarily novel functions in the motor system in primates, including independent voluntary control of finger movements, which are more advanced in primates compared with…”

“Other hypotheses posit that existing genes are modified, including changes in coding sequence, cis-regulatory motifs [16,17] or new alternative mRNA splice variants [18–21], a process known as subfunctionalization [12–14].”

“Gene duplications have been found to influence the development and function of many organs and tissues, including brains, eyes and wings [11,139–147].”

“3 and MiD3cm neurons, or novel duplicated Mauthner cells), followed by a modification of the function of the duplicated element is a common course in evolution at a number of levels of organization (brain regions and pathways: Chakraborty & Jarvis, 2015; genes: Holland & Short, 2008).”

“However, whether such a mechanism play a role in diversifying behaviors remains unclear (Chakraborty and Jarvis, 2015; Katz, 2011; Kirschner and Gerhart, 1998; Tosches, 2017).”

“While humans and song-birds share analogous brain circuits for vocal learning [7], a circuit dedicated to song learning in birds facilitates the study of the underlying neuronal mechanisms [6].”

“We propose that the combination of connectogenesis, artificial morphogenesis, and direct sensory processing enable neurosimulation in ways that simply taking weights and nodes in layers of a disembodied network cannot.”

“…of complex vertebrate structures, such as the auditory system, depends heavily on gene duplication and the subsequent functional diversification of paralogous genes (Chakraborty and Jarvis 2015; Duncan and Fritzsch 2012; Elliott, et al. 2021; Fritzsch and Elliott 2017; Shimeld and Holland 2000).”

“Phylogenetic studies suggest that the current architecture might be the result of the gradual duplication and specialization of ancestral pools of neural modules Cisek [2019], Chakraborty and Jarvis [2015], Feenders et al. [2008].”

“…by changing the intrinsic properties of neurons, the density of neuronal projections, or the number of cells of a given type; most dramatically, it may duplicate entire regions or circuits (Chakraborty and Jarvis 2015; Katz 2016; Katz and Hale 2017; Kebschull et al. 2020; Roberts et al. 2022).”

“…followed by divergence is a driving force in brain evolution ( 5 , 6 ), and is thought to have underlaid the emergence of basal ganglia and cerebellar circuits ( 29 , 30 ), bird and human vocal pathways ( 6 , 31 ), and higher-order cortical areas from primary sensory and motor ones ( 32 , 33 ).”

“How brain pathways and the dynamics of neuropeptides evolved to generate complex social behaviour, as Chakraborty and Jarvis (2015) rightly argued, remains an enigmatic but fundamental question in biology [93].”

“…have been extensively examined (e.g. West-Eberhardt, 1983; Kirkpatrick and Ryan, 1991; Gerhardt, 1994), specific changes in the neural circuits responsible for the evolution of signaling have only recently been identified (e.g. Chakraborty and Jarvis, 2015; Leininger and Kelley, 2015; Katz, 2016).”

“This framework challenges the idea of specialized vocal circuits ( 24 ) and provides a possible solution to the problem of flexibly coordinating speech and movement without requiring dedicated, hard-wired pathways for every possible behavioral combination.”

“Both sexes are, therefore, capable of producing and perceiving warbles, and accordingly, neurobiological sex differences in budgerigars regarding nonvocal motor and auditory pathways have not been established [ 41 ].”

“1a ) [6, 7].”

“As songbirds and humans share the rare and remarkable suite of traits for learned vocalizations (Chakraborty and Jarvis, 2015; Prather et al., 2017), future studies may reveal more direct parallels for neuroestrogens in central auditory circuits”