Neocortex

The neocortex is an important part of the brain in mammals. It is also known as the neopallium, isocortex, or six-layered cortex. This area of the brain helps with many important tasks, such as seeing, hearing, and feeling things, thinking and learning, moving the body, understanding space, and using language.

In humans, the neocortex makes up most of the brain's outer layer, called the cerebral cortex. It is made of six layers, which scientists label from the outside layer inward as I to VI. These layers work together to help us process information and make decisions.

Etymology

The word "neocortex" comes from old languages. "Cortex" is a Latin word meaning "bark" or "rind." The prefix "neo-" is from Greek and means "new." Another name, "neopallium," uses the Latin word "pallium," meaning "cloak." Words like "isocortex" and "allocortex" mix Greek words: "isos" means "same," and "allos" means "other."

Anatomy

The neocortex is the most developed part of the brain, with many layers that help with thinking and sensing. It is made of special cells called grey matter and fibers, and it is very thin, only about the width of a few sheets of paper.

In smaller animals like rats, the neocortex is smooth. But in larger animals like elephants, dolphins, and primates, it has folds that help increase its surface area. The human brain also has these folds, though they look slightly different in each person. The neocortex has six main layers, each with different types of cells and connections. These layers work together to process information and send signals to other parts of the brain and body.

Function

The neocortex is part of the brain that comes from a region called the dorsal telencephalon. It is divided into areas that match the shape of the skull above, including the frontal, parietal, occipital, and temporal lobes. Each area has special jobs. For example, the occipital lobe helps us see, and the temporal lobe helps us hear. In humans, the frontal lobe handles complex thinking and language skills.

The neocortex also helps us with sleep, memory, and learning. It stores important memories and helps send messages from our senses to other parts of the brain. It even affects our sleep patterns by switching between active and resting states in our brain cells.

Clinical significance

When certain diseases affect the part of the brain called the neocortex, they can stop important messages from reaching other brain areas. This can lead to changes in how a person acts, thinks, and remembers. For example, damage in one part of the neocortex can cause a loss of knowledge about facts and events. Special tools can also create similar effects in this brain area.

Evolution

The neocortex is the newest part of the cerebral cortex. It evolved later than another part called the allocortex. In humans, the neocortex makes up 90% of the cerebral cortex and 76% of the entire brain.

For an animal to develop a larger neocortex, its brain must grow big enough to support it. Things like body size, energy use, and lifespan affect how the brain evolves. As the neocortex grew, early animals needed to work together more and compete more. This growth also helped control social behaviors better, leading to more peaceful groups.

The six-layer structure of the neocortex is special to mammals. All mammals have it, but other animals do not. However, birds and reptiles show similar brain functions even without this exact structure. Scientists are still deciding on the best way to describe these similarities.

Neocortex ratio

The neocortex ratio shows how big the neocortex is compared to the rest of the brain. A bigger neocortex ratio is linked to more complex social behaviors and larger group sizes. Humans have a much larger neocortex compared to many other animals. For example, chimpanzees have a ratio of 30:1, while humans have a ratio of 60:1, meaning our neocortex is relatively bigger.