Volume 26, Issue 20, Pages R941-R945 (October 2016) The cryptic cortex  Cyrus Martin  Current Biology  Volume 26, Issue 20, Pages R941-R945 (October 2016) DOI: 10.1016/j.cub.2016.10.005 Copyright © 2016 Terms and Conditions

A folded mind: In this illustration comparing the brains of various animals, the highly folded structure of the mammalian cerebral cortex stands out, becoming especially exaggerated in humans. It is no wonder that neuroanatomists in the early part of the twentieth century, the time when this drawing was done, thought the cortex was unique to mammals. (Illustration from The Outline of Science, J. Arthur Thomson.) Current Biology 2016 26, R941-R945DOI: (10.1016/j.cub.2016.10.005) Copyright © 2016 Terms and Conditions

A layered brain: One of the distinctive features of the mammalian cerebral cortex is its clearly defined layers, as shown in this drawing by the famous neuroanatomist Santiago Ramón y Cajal. Work in the middle to later part of the twentieth century would show that the cells in the different layers function together in radial columns. (From Comparative Study of the Sensory Areas of the Human Cortex, Cajal, 1899.) Current Biology 2016 26, R941-R945DOI: (10.1016/j.cub.2016.10.005) Copyright © 2016 Terms and Conditions

Brainy birds: The term ‘bird brain’ is derogatory and yet we see signs of high cognition in birds. Members of the corvid family are famous for their intelligence, for example, their use of tools for foraging. New Caledonian crows (left) can fashion hooked sticks to pry insects out of trees (photo credit: Jessica van der Wal/Rutz group). And songbirds are capable of vocal learning. In zebra finches (right), for example, young males learn to reproduce the songs of their adult ‘tutor’ (© Jim Bendon, Flickr). Current Biology 2016 26, R941-R945DOI: (10.1016/j.cub.2016.10.005) Copyright © 2016 Terms and Conditions

In search of a reptilian cortex: With evidence in hand that birds may have a cortex-like structure in their brains, the search is now on to explore brains in a wider array of vertebrates, particularly reptiles which are closely related. Sea turtles are known for their navigational abilities, crossing huge distances in the open ocean to reach a preferred beach for egg laying. It’s possible that this ability depends on circuits that are similar to those used for navigation in mammals, such as the hippocampus. (Image: Brocken Inaglory.) Current Biology 2016 26, R941-R945DOI: (10.1016/j.cub.2016.10.005) Copyright © 2016 Terms and Conditions