Developmental structure in brain evolution

Abstract

First, we clarify the central nature of our argument: our attempt is to apportion variation in brain size between developmental constraint, system-specific change, and “mosaic” change, underlining the unexpectedly large role of developmental constraint, but making no case for exclusivity. We consider the special cases of unusual hypertrophy of single structures in single species, regressive nervous systems, and the unusually variable cerebellum raised by the commentators. We defend the description of the cortex (or any developmentally-constrained structure) as a potential spandrel, and weigh the implications of the spandrel concept for the course of human evolution. The empirical and statistical objections raised in the commentary of Barton are discussed at length. Finally, we catalogue and comment on the suggestions of new ways to study brain evolution, and new aspects of brain evolution to study.

Brain volumes and Val66Met polymorphism of the BDNF gene: local or global effects?

“…The univariate allometric equation y = bx a has been widely used to study the relationship in the size of different structures of the vertebrate brain (Jerison 1973;Finlay et al 2001). Depending on the value of a, this equation can describe two structures whose volume is directly proportional (a = 1), or a structure whose volume is non-linearly related to the volume of the other (a [ 1 for a disproportionate increase, a \ 1 for a decrease).…”

Morphometric analysis of the AMPA-type neurons in the Deiters vestibular complex of the chick brain

“…If it is not always simple to evaluate close species it is incredibly harder to compare remote groups. Afterward, the number of cells associated with neural connections, glial support, and vascularization would be considered as functional regulators of total number of cells (Finlay et al, 2001). Any comparison of specific brain areas controlling functions should take this in relevance, although in view of our data, DC presented a comparable LVN structure suggesting proximity of the physiological magnitude (under a behavioral point-of-view) of the postural adjustments in birds and mammals.…”

“…Except for the almost absence of giant neurons containing GluR2/3 at the caudal pole, no differences were notice concerning location preference or subunit immunoreactivity in the dND of chicks. tends to increase in the course of vertebrate phylogenesis taking place similarly in different linkages (Finlay et al, 2001). Through mathematical modeling, Striedter (2005) showed that the brain of birds exceeds those from reptiles of the same size up 4-6 times, presenting a high parallel with mammals.…”

Ecological constraints on the evolution of avian brains

“…Which structure is bigger or smaller depends on the conservative order in neurogenesis. It has therefore been argued that (in mammalian brains) variation in most regions is simply a consequence of a functionally driven change in one or very few other regions, with a disproportionately large growth occurring in late-generated parts (Finlay and Darlington 1995;Finlay et al 2001). These byproducts of neurogenetic changes may set the 'frame' that can be utilized by various behaviors, which in turn may modify the neurogenetic substrate.…”