Domestic dogs (Canis lupus familiaris) exhibit a wide range of cranial morphologies. This diversity in skull shape is largely the result of modern selective breeding practices. This project investigates the impact of selection for facial reduction on canine neuroanatomy. Previous research has indicated that the breeding for reduced faces in dogs has led to global impacts in the shape of their skull and mandible. This previous research has largely failed to consider, however, the impact of these breeding practices on the soft neuroanatomical tissue. We generated endocasts from an existing set of clinically‐obtained CT scans. This sample consists of a variety of dogs with various cranial morphologies representing four known breeds as well as a comparative sample of dogs of unknown breed. We recorded three‐dimensional coordinate data for 31 landmarks representing various gyri, sulci, and other neuroanatomical landmarks. Placing landmarks at these locations allowed us to analyze differences in shape of the endocasts. Using geometric morphometric analysis, we found that the endocast shape variance in this sample is correlated with cephalic index and as a result, it is clear that selection for facial reduction has caused a perceivable effect on canine neuroanatomy. Furthermore, we found that the majority of the shape variance in the sample was associated with olfactory anatomy. Despite this fact, when the olfactory anatomy‐associated landmarks were excluded from the sample, the rest of the brain morphology was also correlated with cephalic index. The results of this project indicate that modern breeding practices, specifically the selection for dogs with squished faces, have significantly impacted canine neuroanatomy.

The range of cranial morphology seen in domestic dogs (Canis lupus familiaris) is a direct result of thousands of years of selective breeding. This article is the first to investigate how selection for reduced faces in brachycephalic dogs impacted the neuroanatomy of the canine brain through the analysis of endocasts. Previous research has demonstrated global effects on the shape of the bony cranium as the result of these breeding practices; however, these studies have largely focused on the bony structures of the skull and failed to consider the influence of facial reduction on the soft tissues of the brain. We generated endocasts from an existing set of clinically‐obtained CT scans representing a variety of dogs with various cranial morphologies. These dogs represented four breeds as well as a comparative sample of dogs of unknown breed. We recorded three‐dimensional coordinate data for 31 landmarks representing various gyri, sulci, and other neuroanatomical landmarks that allowed us to analyze differences in shape of the endocasts. Through geometric morphometric analyses, we determined that the endocast shape variance in this sample is correlated with cephalic index, and thus the selection for facial reduction has caused a perceivable effect on canine neuroanatomy. Additionally, we found the majority of the shape variance in the sample to be associated with olfactory anatomy; however, the rest of the morphology also correlates with cephalic index. The results of this article indicate that modern breeding practices and the selection for dogs with short faces have significantly influenced canine neuroanatomy.