Let's take a walk along the cortical ribbon

By Kevin S. Weiner

When you hear the word ribbon, you might think of wrapping presents or maybe a yellow, red, or blue satin award you won when you were seven (or even yesterday). You probably don’t think that an integral part of what contributes to your thoughts and perceptions is a strip of neural tissue known as the cortical ribbon. So, while we collate and finish up our new posts for you about the highlights from our annual Human Brain Mapping meeting in Geneva that we spoke about last time, come take a walk with us along the cortical ribbon.

The cortical ribbon is a strip about 3mm wide (about how much your fingernail grows in a month) that comprises the outer most portion of our brains. The ribbon itself consists of six layers and within each layer, there are neurons, or nerve cells. The organization of these cells across layers generates an organization, or architecture, that differs from one brain area to the next.

The cortical ribbon. Top left: Photograph of a postmortem brain removed from the skull. Top right: A single brain section removed from the red line at left. The top half of the section depicts right and left hemispheres of the cortex. The cortical ribbon is the dark outline that you see running along the perimeter of each hemisphere. The bottom half of the section (the really squiggly stuff) is the cerebellum. Bottom: This is a zoomed image of the section within the red square in the top right. Portions of the cortical ribbon have been numbered. You can think of the cortical ribbon as a track of gray matter surrounding white matter, which we will learn about in future posts. IMAGE ADAPTED FROM CASPERS ET AL., 2013

And these differences in architecture contribute to different functions that these brain areas perform. So, if you were to play brain tourist and take a walk along the cortical ribbon, you would see different types of architecture. Presently, there are algorithms that identify boundaries between one brain area and the next (summarized here) without us ever needing to pick up a microscope. These boundaries are essentially like the demarcations that separate one state from another in the U.S. However, if you were to walk along the cortical ribbon, it’s highly unlikely that you would be greeted with signs when you cross into a new brain area like you are when you cross state lines and see ‘Welcome to New Jersey!’

It’s important to note that some of these architectural differences are not sharp and instead, are rather fuzzy between areas. Nevertheless, boundaries between systems are clear. For example, areas of the visual system that help us see look quite different compared to areas of the motor system that help us move. However, areas do not have to be in different systems to look different. Even areas that are adjacent to one another and that are part of the same system can look different across these six layers of the cortical ribbon. These differences in structure have been linked to differences in function, which we will continue to unpack further in future posts.

So, the next time you remove a ribbon when you open a present, think of your brain and all the different things it opens up for you to help you perceive the world around you.

Originally published by HuffPost