TY - JOUR
T1 - Comparative analysis of cortical layering and supragranular layer enlargement in rodent carnivore and primate species
AU - Hutsler, Jeffrey J.
AU - Lee, Dong Geun
AU - Porter, Kristin K.
PY - 2005/8/2
Y1 - 2005/8/2
N2 - The mammalian cerebral cortex is composed of individual layers characterized by the cell types they contain and their afferent and efferent connections. The current study examined the raw, and size-normalized, laminar thicknesses in three cortical regions (somatosensory, motor, and premotor) of fourteen species from three orders of mammals: primates, carnivores, and rodents. The proportional size of the pyramidal cell layers (supra- and infragranular) varied between orders but was similar within orders despite wide variance in absolute cortical thickness. Further, supragranular layer thickness was largest in primates (46 ± 3 percent), followed by carnivores (36 ± 3 percent), and then rodents (19 ± 4 percent), suggesting a distinct difference in the proportion of cortex devoted to corticocortical connectivity across these orders. Although measures of supragranular layer thickness are highly correlated with measures of overall brain size, such associations are not present when independent contrasts are used to control for phylogenetic inertia. Interestingly, neurogenesis time span remains strongly associated with supragranular layer thickness despite size normalization and controlling for phylogenetic inertia. Such layering differences between orders, and similarities amongst species within an order, suggest that supragranular layer expansion may have occurred early in mammalian evolution and may be related to ontogenetic variables such as neurogenesis time span rather than measures of overall size.
AB - The mammalian cerebral cortex is composed of individual layers characterized by the cell types they contain and their afferent and efferent connections. The current study examined the raw, and size-normalized, laminar thicknesses in three cortical regions (somatosensory, motor, and premotor) of fourteen species from three orders of mammals: primates, carnivores, and rodents. The proportional size of the pyramidal cell layers (supra- and infragranular) varied between orders but was similar within orders despite wide variance in absolute cortical thickness. Further, supragranular layer thickness was largest in primates (46 ± 3 percent), followed by carnivores (36 ± 3 percent), and then rodents (19 ± 4 percent), suggesting a distinct difference in the proportion of cortex devoted to corticocortical connectivity across these orders. Although measures of supragranular layer thickness are highly correlated with measures of overall brain size, such associations are not present when independent contrasts are used to control for phylogenetic inertia. Interestingly, neurogenesis time span remains strongly associated with supragranular layer thickness despite size normalization and controlling for phylogenetic inertia. Such layering differences between orders, and similarities amongst species within an order, suggest that supragranular layer expansion may have occurred early in mammalian evolution and may be related to ontogenetic variables such as neurogenesis time span rather than measures of overall size.
KW - Column
KW - Cortex
KW - Evolution
KW - Mammal
UR - http://www.scopus.com/inward/record.url?scp=23744472001&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=23744472001&partnerID=8YFLogxK
U2 - 10.1016/j.brainres.2005.06.015
DO - 10.1016/j.brainres.2005.06.015
M3 - Article
C2 - 16018988
AN - SCOPUS:23744472001
VL - 1052
SP - 71
EP - 81
JO - Brain Research
JF - Brain Research
SN - 0006-8993
IS - 1
ER -