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 ev..., Animals
We used 3-4-month-old Swiss-Webster female mice from the selection experiment carried out at the Faculty of Biology, University of Bialystok. We divergently select mice for high/low body mass-corrected Basal Metabolic Rate (BMR). In this experiment, we maintain two non-replicated line types: the high-BMR (H-BMR) and low-BMR (L-BMR) line type. Individual mice used in this study were randomly drawn from a stock of animals not qualified for further selection.
The divergence achieved in the primarily selected trait- BMR is sufficiently large to be confidently attributed to the results of the selection, rather than to genetic drift.. Still, however, a straightforward statistical comparison of both selection line types with respect to the traits that are not directly selected, such as those analyzed in our study is questionable, because in their case one cannot rule out that the differences between the L-BMR and H-BMR mice were due to random effects unrelated the applied selection. To..., , # **Evolution of cellular architecture and function of the hippocampus: Insights from the artificial selection experiment**

[https://doi.org/10.5061/dryad.fqz612jxv](https://doi.org/10.5061/dryad.fqz612jxv)

**Description of the data and file structure**

The Excel file ‘RSBL_Data_File’ contains all raw data used in the analyses in the manuscript accepted in Biology Letters. Subsequent folders contain the following data sets:

* **Hippocampal area**: total cross-sectional surface area (µm2) of the hippocampus- the brain structure underlying cognitive abilities. Hippocampal area is used as a proxy of its size.

**Missing data denoted as '.'**

**Line type**: code of the line type

**Subline:** code of the replicated subline within line type

**ID** code of an animal

**Side** code of the brain side (Left, Right)

**P146, P182, P230, P270** cross-sectional surface area (µm2) of the hippocampus area positioned at  -1.46, -1.82, -2.30, -2.70 mm respectively from bregma

* **Pyramidal Cell ...,