THE DINOSAUR BRAIN
How they’re organised, what the different parts do and why bigger might be better
Dinosaur brains are long and tubular, as can be seen in the T. rex brain above. The largest region is usually the telencephalon, comprised principally of the left and right cerebral hemispheres: the seat of intelligence and sensory functions. At the front of the telencephalon are the olfactory bulbs that control the sense of smell, and behind it are the optic lobes of the diencephalon that power vision. A small midbrain region (mesencephalon) separates the diencephalon from the hindbrain (rhombencephalon). The rhombencephalon is further divided into the cerebellum, which plays a role in motor function, and the medulla, from which emerge the cranial nerves that control breathing, heart rate, blood pressure and other involuntary functions. A lobe of the cerebellum called the flocculus emerges laterally; it helps regulate eye, neck and head movements.
On the sides of the brain are the inner ears, which consist of the pretzel-shaped semicircular canals that are filled with fluid to help regulate balance and head stabilisation. Beneath are the long cochlea, which control hearing. A number of air-filled sinuses emanating from the inner ear surround the sides of the brain, possibly helping to cool the brain or to enhance hearing. Other blood-filled sinuses cushion the sides and top of the brain.
The size of the brain can be used to estimate intelligence. Although measuring intelligence is riddled with uncertainties, there is a straightforward measure to roughly compare the intelligence of different animals: the encephalisation quotient (EQ). It’s basically a measure of the relative size of the brain compared to the size of the body. Large animals usually have larger brains than smaller animals, even if they’re not more intelligent, so the larger the EQ, the bigger the brain is relative to its expected value for the animal’s size, and thus the more intelligent the animal is considered to be.