Cortex: Definition, Function & Layers

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  • 0:03 Defining the Cortex
  • 0:38 Anatomy of the Cerebral Cortex
  • 1:58 Function
  • 2:16 Cortices
  • 3:16 Lesson Summary
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Lesson Transcript
Instructor: Sarah Phenix
In this lesson, we are going to explore what the word ~'cortex~' means and then focus on its application to the cerebral cortex and explore the areas, functions, and structures within this area of the brain.

Defining the Cortex

Before we jump into this lesson, we should take a moment to define the term cortex. You might not realize it, but cortex doesn't implicitly have anything to do with the brain. In anatomical terms, cortex means the outermost layer of tissue. In other words, the brain isn't the only organ in your body that has a cortex. For example, the kidneys, adrenal glands, thymus, and lymph nodes also have a cortex (or cortices would be the plural form of the word).

In this lesson, we are discussing the cerebral cortex. Cerebral means pertaining to the brain.

Anatomy of the Cerebral Cortex

The cerebral cortex is the outermost layer of the brain, which you might have also heard referred to as gray matter. Gray matter gets its name from the gray coloration of the unmyelinated (meaning they are lacking the fatty, insulatory myelin sheath) nerve cells that compose it. This is notably different from the underlying medulla of the brain, also called the white matter, which is composed of myelinated nerve fibers and so appears white.

The shallow invaginations (or grooves) that are so prominent in the cerebral cortex are called sulci and are formed by the folds of twisting tissue called gyrus. These structures, along with the large fissures that divide the brain into different hemispheres, the left and right hemisphere, and into four different lobes, including the frontal, parietal, temporal, and occipital lobes, serves to increase the surface area of the brain.

So why is surface area important? Well, gray matter is the super computer that runs all of the complex systems of our bodies, and it makes us who we are. By folding the tissue in these complex gyrus, it means that we can fit more neuron-containing tissue within our skulls. In other words, more wrinkles will mean more neurons, and more neurons means a much greater intellectual capacity. This is one instance where the more wrinkles you have, the better!


The cerebral cortex plays a role in just about every neural process, like memory, perception, attention, awareness, consciousness, thought, language, problem-solving, advanced motor functions, and social abilities. So, suffice it to say, it's a pretty important area of the brain.


That's right, there are cortices in the cerebral cortex! These cortices are not necessarily large, isolated regions, as the lobes of the brain are, but are specific gyrus that govern certain aspects of how we function and are interspersed throughout the lobes:

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