THE DI­NOSAUR BRAIN

How they’re or­gan­ised, what the dif­fer­ent parts do and why big­ger might be bet­ter

Focus-Science and Technology - - Palaeontology -

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.

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