Organizational Conservation and Flexibility in the Evolution of Birdsong and Avian Motor Control

Abstract

Birds and mammals have independently evolved complex behavioral and cognitive capabilities yet have markedly different brain structures. An open question is to what extent, despite these differences in anatomy, birds and mammals have evolved similar neural solutions to complex motor control and at what level of organization these similarities might lie. Courtship song in songbirds, a learned motor skill that is similar to the fine motor skills of many mammals including human speech, provides a powerful system in which to study the links connecting the development and evolution of cells, circuits, and behavior. Until recently, obtaining cellular-resolution views of the specialized neural circuitry that subserves birdsong was impossible due to a lack of molecular tools for songbirds. However, the ongoing revolution in cellular profiling and genomics offers unprecedented opportunities for molecular analysis in organisms that lack a traditional genetic infrastructure but have tractable, well-defined behaviors. Here, I describe recent efforts to understand the evolutionary relationships between birdsong control circuitry and mammalian neocortical circuitry using new approaches to measure gene expression in single cells. These results, combined with foundational work relating avian and mammalian brains at a range of biological levels, present an emerging view that amniote pallium evolution is a story of diverse neural circuit architectures employing conserved neuronal elements within a conserved topological framework. This view suggests that one locus of pallial neural circuit evolution lies at the intersection between the gene regulatory programs that control regional patterning and those that specify functional identity. Beyond birdsong, modifications to this intersection may underlie the evolution of general motor circuitry in the bird pallium and the developmental relationship between these circuits and the avian pallial amygdala.

Cannabidiol inhibits neuroinflammatory responses and circuit-associated synaptic loss following damage to a songbird vocal pre-motor cortical-like region

“…The value of studying CBD neuroprotection in songbirds lies in ability to identify processes modified within discrete nodes of circuits controlling vocal learning and production. Vocal control pathways in both songbirds and humans share convergent functional similarities that increase translational relevance relative to non-vocal learning species 9 , 10 . A distinct difference between avian and human vocal pathways is nuclear rather than laminated organization of pallial vocal control regions.…”

“…Also like humans, songbird vocal learning depends upon establishment of circuits linking cortical, striatal and thalamic brain regions 7 . Gene expression profiles demonstrate distinct similarities between songbird and human vocal learning 8 , 9 and motor regions 10 . For example, evidence supports functional similarities between human laryngeal motor cortex (LMC) layers 2, 3 and 6 and songbird HVC (proper name), that each drive vocal motor output (from LMC layer 5 and songbird robust nucleus of the arcopallium [RA], respectively 9 ).…”

Cannabidiol Inhibits Neuroinflammatory Responses and Circuit-Associated Synaptic Loss Following Damage to a Songbird Vocal Pre-motor Cortical-Like Region

“…The value of studying CBD neuroprotection in songbirds lies in ability to identify processes modi ed within discrete nodes of circuits controlling vocal learning and production. Vocal control pathways in both songbirds and humans share convergent functional similarities that increase translational relevance relative to nonvocal learning species 9,10 . A distinct difference between avian and human vocal pathways is nuclear rather than laminated organization of pallial vocal control regions.…”

“…Also like humans, songbird vocal learning depends upon establishment of circuits linking cortical, striatal and thalamic brain regions 7 . Gene expression pro les demonstrate distinct similarities between songbird and human vocal learning 8,9 and motor regions 10 . For example, evidence supports functional similarities between human laryngeal motor cortex (LMC) layers 2, 3 and 6 and songbird HVC (proper name), that each drive vocal motor output (from LMC layer 5 and songbird robust nucleus of the arcopallium [RA], respectively 11 ).…”

Wintering molecular changes in the brain of Calidris pusilla at lower latitude

“…We quanti ed differentially expressed genes of recently arrived and premigratory individuals and used information from genomic studies of other species to speculate about the functional signi cance of this differential expression. The underlying assumption was that genomic functional regions are conserved in birds and mammals through evolution (Colquitt, 2022;Guigo & de Hoon, 2018). Although this is a limited way to interpret the results (Colquitt, 2022;…”