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Developmental Modes and Developmental Mechanisms can Channel Brain Evolution.

Charvet CJ, Striedter GF - Front Neuroanat (2011)

Bottom Line: We suggest that altriciality facilitates the evolution of telencephalic expansion by delaying telencephalic neurogenesis.We further hypothesize that delays in telencephalic neurogenesis generate delays in telencephalic maturation, which in turn foster neural adaptations that facilitate learning.Overall, we argue that developmental modes have influenced how some lineages of birds increased the size of their telencephalon and that this, in turn, has influenced subsequent changes in brain circuits and behavior.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California Irvine, CA, USA.

ABSTRACT
Anseriform birds (ducks and geese) as well as parrots and songbirds have evolved a disproportionately enlarged telencephalon compared with many other birds. However, parrots and songbirds differ from anseriform birds in their mode of development. Whereas ducks and geese are precocial (e.g., hatchlings feed on their own), parrots and songbirds are altricial (e.g., hatchlings are fed by their parents). We here consider how developmental modes may limit and facilitate specific changes in the mechanisms of brain development. We suggest that altriciality facilitates the evolution of telencephalic expansion by delaying telencephalic neurogenesis. We further hypothesize that delays in telencephalic neurogenesis generate delays in telencephalic maturation, which in turn foster neural adaptations that facilitate learning. Specifically, we propose that delaying telencephalic neurogenesis was a prerequisite for the evolution of neural circuits that allow parrots and songbirds to produce learned vocalizations. Overall, we argue that developmental modes have influenced how some lineages of birds increased the size of their telencephalon and that this, in turn, has influenced subsequent changes in brain circuits and behavior.

No MeSH data available.


Related in: MedlinePlus

Comparative analysis of avian post-hatching brain growth is measured by the ratio of adult to hatchling brain weight. Altricial species with proportionally small telencephalons (e.g., swifts and pigeons) exhibit more post-hatching brain growth than precocial species (e.g., anseriform and galliform birds). Parrots and songbirds (i.e., oscine passerines) exhibit even more post-hatching brain growth than many other altricial species. Among songbirds, corvids (carrion crows, magpies) exhibit some of the largest post-hatching brain growth. Because the telencephalon is born late in development, post-hatching brain growth is due primarily to the expansion of the telencephalon (see Striedter and Charvet, 2008; Charvet and Striedter, 2009a). Data are from Portmann (1947b).
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Figure 3: Comparative analysis of avian post-hatching brain growth is measured by the ratio of adult to hatchling brain weight. Altricial species with proportionally small telencephalons (e.g., swifts and pigeons) exhibit more post-hatching brain growth than precocial species (e.g., anseriform and galliform birds). Parrots and songbirds (i.e., oscine passerines) exhibit even more post-hatching brain growth than many other altricial species. Among songbirds, corvids (carrion crows, magpies) exhibit some of the largest post-hatching brain growth. Because the telencephalon is born late in development, post-hatching brain growth is due primarily to the expansion of the telencephalon (see Striedter and Charvet, 2008; Charvet and Striedter, 2009a). Data are from Portmann (1947b).

Mentions: Altricial and precocial species also differ in the timing of brain maturation. Specifically, altricial species delay some aspects of brain maturation into the post-hatching period relative to precocial species. This is most evident from the observation that altricial (including semi-altricial) species such as parrots, songbirds, owls, and pigeons generally exhibit more post-hatching brain growth than precocial species (Figure 3). Given this delayed brain growth, we can infer that late-born brain regions, such as the telencephalon, are functionally immature at hatching in altricial species (Portmann, 1947b; Finlay and Darlington, 1995; Ling et al., 1997; Finlay et al., 1998; Striedter and Charvet, 2008). This delayed brain maturation presumably renders altricial hatchlings relatively helpless and dependent on their parents.


Developmental Modes and Developmental Mechanisms can Channel Brain Evolution.

Charvet CJ, Striedter GF - Front Neuroanat (2011)

Comparative analysis of avian post-hatching brain growth is measured by the ratio of adult to hatchling brain weight. Altricial species with proportionally small telencephalons (e.g., swifts and pigeons) exhibit more post-hatching brain growth than precocial species (e.g., anseriform and galliform birds). Parrots and songbirds (i.e., oscine passerines) exhibit even more post-hatching brain growth than many other altricial species. Among songbirds, corvids (carrion crows, magpies) exhibit some of the largest post-hatching brain growth. Because the telencephalon is born late in development, post-hatching brain growth is due primarily to the expansion of the telencephalon (see Striedter and Charvet, 2008; Charvet and Striedter, 2009a). Data are from Portmann (1947b).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3037498&req=5

Figure 3: Comparative analysis of avian post-hatching brain growth is measured by the ratio of adult to hatchling brain weight. Altricial species with proportionally small telencephalons (e.g., swifts and pigeons) exhibit more post-hatching brain growth than precocial species (e.g., anseriform and galliform birds). Parrots and songbirds (i.e., oscine passerines) exhibit even more post-hatching brain growth than many other altricial species. Among songbirds, corvids (carrion crows, magpies) exhibit some of the largest post-hatching brain growth. Because the telencephalon is born late in development, post-hatching brain growth is due primarily to the expansion of the telencephalon (see Striedter and Charvet, 2008; Charvet and Striedter, 2009a). Data are from Portmann (1947b).
Mentions: Altricial and precocial species also differ in the timing of brain maturation. Specifically, altricial species delay some aspects of brain maturation into the post-hatching period relative to precocial species. This is most evident from the observation that altricial (including semi-altricial) species such as parrots, songbirds, owls, and pigeons generally exhibit more post-hatching brain growth than precocial species (Figure 3). Given this delayed brain growth, we can infer that late-born brain regions, such as the telencephalon, are functionally immature at hatching in altricial species (Portmann, 1947b; Finlay and Darlington, 1995; Ling et al., 1997; Finlay et al., 1998; Striedter and Charvet, 2008). This delayed brain maturation presumably renders altricial hatchlings relatively helpless and dependent on their parents.

Bottom Line: We suggest that altriciality facilitates the evolution of telencephalic expansion by delaying telencephalic neurogenesis.We further hypothesize that delays in telencephalic neurogenesis generate delays in telencephalic maturation, which in turn foster neural adaptations that facilitate learning.Overall, we argue that developmental modes have influenced how some lineages of birds increased the size of their telencephalon and that this, in turn, has influenced subsequent changes in brain circuits and behavior.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, University of California Irvine, CA, USA.

ABSTRACT
Anseriform birds (ducks and geese) as well as parrots and songbirds have evolved a disproportionately enlarged telencephalon compared with many other birds. However, parrots and songbirds differ from anseriform birds in their mode of development. Whereas ducks and geese are precocial (e.g., hatchlings feed on their own), parrots and songbirds are altricial (e.g., hatchlings are fed by their parents). We here consider how developmental modes may limit and facilitate specific changes in the mechanisms of brain development. We suggest that altriciality facilitates the evolution of telencephalic expansion by delaying telencephalic neurogenesis. We further hypothesize that delays in telencephalic neurogenesis generate delays in telencephalic maturation, which in turn foster neural adaptations that facilitate learning. Specifically, we propose that delaying telencephalic neurogenesis was a prerequisite for the evolution of neural circuits that allow parrots and songbirds to produce learned vocalizations. Overall, we argue that developmental modes have influenced how some lineages of birds increased the size of their telencephalon and that this, in turn, has influenced subsequent changes in brain circuits and behavior.

No MeSH data available.


Related in: MedlinePlus