Data from: Evolution of cellular architecture and function of the hippocampus: Insights from the artificial selection experiment

Inter-specifically, mammalian species having larger brains built of more
numerous neurons have higher cognitive abilities (CA), but at the expense
of higher metabolic costs. It is unclear, however, how this pattern
emerged, since evolutionary mechanisms act intra-specifically, not
inter-specifically. Here we tested the existence of the above pattern at
the species level in the hippocampus- the brain structure underlying CA.
We used the experimental evolution model system consisting of lines of
laboratory mice divergently selected for basal metabolic rate (BMR) - a
trait implicated in the evolution of brain size, its metabolic costs and
CA. Selection on BMR did not affect hippocampus size. Yet, the high BMR
mice had superior CA and manifested increased neuronal density, higher
cytochrome C oxidase density (indexing metabolic costs of neuronal
activity) and dendritic spine density (indexing connectivity between
neurons). Thus, our study calls into question generality of patterns of
the evolution of CA apparent interspecifically. At the species level
increased CA may arise through re-arrangement of the architecture and
function of neurons, without a conspicuous increase of their size.