Fig. 6. Brain atrophy is evident in aged dogs and in humans.

We used the relative volume of lateral ventricles as an index of brain atrophy in dogs (a, b) and humans (c¹⁸⁴). b Plots of the relative lateral ventricles volume versus chronological age show that the lateral ventricles expand with age, but that this largely occurs at 12 years of age and beyond in dogs and at (c) 60 years and beyond in humans¹⁸³. The relative lateral ventricle volumes in humans were computed by dividing the lateral ventricle volumes by the cerebral cortex gray, white matter, and lateral ventricle volumes¹⁸⁴. The dog brains are redrawn from a structural MRI scan of a 2- and 15-year-old beagle available at: https://veteriankey.com/the-effects-of-aging-on-behavior-in-senior-pets/.