Brain gyrification in wild and domestic canids: Has domestication changed the gyrification index in domestic dogs?

Abstract

Over the last 15 years, research on canid cognition has revealed that domestic dogs possess a surprising array of complex sociocognitive skills pointing to the possibility that the domestication process might have uniquely altered their brains; however, we know very little about how evolutionary processes (natural or artificial) might have modified underlying neural structure to support species‐specific behaviors. Evaluating the degree of cortical folding (i.e., gyrification) within canids may prove useful, as this parameter is linked to functional variation of the cerebral cortex. Using quantitative magnetic resonance imaging to investigate the impact of domestication on the canine cortical surface, we compared the gyrification index (GI) in 19 carnivore species, including six wild canid and 13 domestic dog individuals. We also explored correlations between global and local GI with brain mass, cortical thickness, white and gray matter volume and surface area. Our results indicated that GI values for domestic dogs are largely consistent with what would be expected for a canid of their given brain mass, although more variable than that observed in wild canids. We also found that GI in canids is positively correlated with cortical surface area, cortical thickness and total cortical gray matter volumes. While we found no evidence of global differences in GI between domestic and wild canids, certain regional differences in gyrification were observed.

Brain of the African wild dog. I. Anatomy, architecture, and volumetrics

“…The average cortical gyrencephalic index measured in the African wild dog was 1.76 ( SD = 0.03). Recent allometric analyses in the Carnivora revealed a strong hypoallometric relationship between brain mass and GI (Grewal et al, 2020). Here we reproduced a subset of the Carnivora data from Grewal et al (2020) as shown in Figure 9 and demonstrate that the mean GI for the African wild dog is very close to what would be predicted for a carnivore with a brain mass of around 160 g (Figure 9).…”

“…One example of this is the finding that volumetric changes in the size of the lateral cerebellar hemispheres (independent of cerebellar size) are correlated with measures of domain‐general cognition in primates (Smaers, Turner, Gomez‐Robles, & Sherwood, 2018). Similarly, Grewal et al (2020) point out that local gyrification differences (in the Canidae) of potential functional significance may be masked by more global differences in cortical folding and thus, in order to explain the behavioral specializations exhibited by the African wild dog, a more in‐depth analysis of structural‐functional differences is required.…”

“…Using Phylogenetic Generalized Least Squares (PGLS) regression analysis we quantitatively compared the average values for the African wild dog with allometric data obtained from a subset of other mammals used in previous studies by our group (Grewal et al, 2020;Manger et al, 2010Manger et al, , 2012Maseko et al, 2011Maseko et al, , 2012Patzke et al, 2015;Pillay & Manger, 2007;Spocter, Uddin, et al, 2018). Our goal here was not to re-evaluate the published data but rather to show through superimposition where the average values for the African wild dog are found in relation to other mammals.…”

“…One example of this is the finding that volumetric changes in the size of the lateral cerebellar hemispheres (independent of cerebellar size) are correlated with measures of domain-general cognition in primates (Smaers, Turner, Gomez-Robles, & Sherwood, 2018). Similarly, Grewal et al (2020)…”

The Digital Brain Bank, an open access platform for post-mortem datasets

“…In this context, post-mortem MRI data are important because they share common signal forming mechanisms with in vivo MRI and a common tissue state with microscopy, providing a framework for investigation across multiple spatial scales. Postmortem MRI facilitates comparative anatomy investigations in species that are not traditionally accessible for in-vivo imaging (Berns et al, 2015;Bhagwandin, Haagensen, & Manger, 2017;Grewal et al, 2020;Heuer et al, 2019), including extinct species (Berns & Ashwell, 2017). Long post-mortem scans provide the opportunity to push the boundaries of spatial resolution, providing whole human brain coverage reaching voxel sizes of 100-500 μm (Edlow et al, 2019;Foxley et al, 2016;Fritz et al, 2019;Weigel et al, 2021), edging closer to microscopy techniques but benefitting from compatibility with in-vivo imaging.…”