Impact of selection pressure for social behavior on canid brain evolution

Emory University, Atlanta GA

Investigators

Abstract

This project will investigate features of neural system organization that can be linked to altered social behavior, including reduced or increased aggression. Two species of canids, experimentally domesticated silver foxes (Vulpes vulpes) and domestic dogs (Canis familiaris), have been selectively bred by humans for altered social behavior. These behavioral changes occurred alongside a restricted set of genetic changes, creating an unparalleled opportunity to link the evolution of behavioral characteristics (phenotypes) to neural phenotypes. Recent technological advancements enable detailed, non-invasive studies of brain anatomy at relatively low cost. This project will take advantage of these innovations to create high-resolution three-dimensional (3D) brain maps using structural magnetic resonance imaging, diffusion tensor imaging, and digitized histology. Expected products of this research include: (1) identification of features of neural organization that are linked to reduced or increased sociality or aggression, expected to be generalizable to other species, (2) the production of online fox and dog brain atlases that will be publicly available as a research tool for the general scientific community, (3) training opportunities for young scientists, and (4) outreach efforts using blog and social media posts for the general public. Because dogs are a "common denominator" across various cultures, this research has a unique opportunity to be personally relevant and compelling to people from all walks of society, and to enhance public appreciation for science. Both experimentally-domesticated foxes and domestic dogs are distinguished from their wild forebears by altered social approach-avoidance behavior. Previous research in rodents and primates, and the researchers' own preliminary data, allow for the formation of well-grounded hypotheses about neural adaptations that result from selection pressure on social approach-avoidance behavior. Specifically, this project will investigate limbic and fronto-limbic systems governing social behavior and response selection. In order to identify features of neural system organization associated with altered social behavior, whole-brain white and gray matter organization will be compared (a) between various breeds of domestic dogs, each tested for social approach-avoidance/aggression behavior, and (b) between strains of foxes bred for social avoidance behavior, which react aggressively to social contact, versus foxes bred for social approach behavior, which are tame and friendly like dogs, versus wild type foxes. Whole-brain MRI and DTI images will be collected using 3.0 and 9.4 Tesla MRI scanners. Histology images will be digitally scanned and aligned to MRI images. Analyses will include voxel-based morphometry, tract-based spatial statistics, probabilistic tractography, and k-means connectivity-based parcellation. The research will advance knowledge about how evolution modified brain organization in response to selection for social approach and avoidance.