The vertebral artery blood supply to the brain and its relationship with cognition across the taxonomic classes: Mammalia and Aves

Lunn, Andrew; Winder, Isabelle C.; Shaw, Vivien

Abstract

Human brains require the most energy per unit of mass of any animal and also have the largest cortical neuron count, which is afforded by having the largest primate brain and abiding by economic scaling rules. Cortical neuron count is one of the most useful biological indicators of intelligence but providing neurons with enough energy requires a high blood supply (achieved through internal carotid and vertebral arteries). Vertebral arteries pass through cervical vertebrae transverse foramina before joining to form the basilar artery, which, with several connecting arteries and the internal carotids, forms the circle of Willis. The circle of Willis, although highly variable in humans, exhibits a less well-developed connection in animals considered ‘less intelligent’, such as Artiodactyls. We hypothesised that if viable neuron count has a relationship with total cerebral circulation, then a relationship may exist between vertebral blood flow and animal cognition. We conducted geometric morphometrics on 40 Mammalia and 26 Aves, measuring cervical vertebrae transverse foramen area, as a proxy to vessel size and an accurate representation of arterial blood flow to the brain. Foramen area was subsequently calculated as a proportion of the vertebral canal, to adjust for organism size across the dataset. We then compared the foramen area with a measure of ‘cognitive complexity’, obtained by counting how many of 12 indicators of complex cognition (broadly encompassing theory of mind, social/emotional intelligence, tool use and mental time travel) each species demonstrated within the literature. Linear regressions showed a positive significant relationship within Mammalia but not when assessed within taxonomic order. Aves also showed a positive relationship between foramen area and cognition, but this should be interpreted with caution due to the low sample size. AIC models and regressions assessed this study’s indicators of cognition against established literature-sourced indicators and showed our ranking system was an accurate representation of what currently constitutes intelligence within the literature. The foramen area also showed a positive correlation with literature-sourced indicators but was influenced by brain size. This study’s results provide an insight into the role of the cerebral circulation and its relationship to Mammalian cognition and might have implications for our own evolution.

Citation

Lunn, A., Winder, I. C., & Shaw, V. (2021, July). The vertebral artery blood supply to the brain and its relationship with cognition across the taxonomic classes: Mammalia and Aves. Poster presented at Anatomical Society Summer Meeting 2021: Cutting Edge Anatomy, Glasgow

• Presentation Conference Type: Poster
• Conference Name: Anatomical Society Summer Meeting 2021: Cutting Edge Anatomy
• Start Date: Jul 8, 2021
• Publication Date: Jul 8, 2021
• Deposit Date: Oct 22, 2021
• DOI: https://doi.org/10.1111/joa.13592
• Public URL: https://hull-repository.worktribe.com/output/3858420
• Additional Information: Published in Journal of Anatomy, Volume 240, Issue 4, April 2022, pages 775-819.; Conference poster 31 YIO:8.