What is a Brain?

The brain is a network of interconnected cells that communicate through electrical and chemical impulses. Its unique structure facilitates its fantastic capabilities.

Similar to how the Earth is ensheathed in crust, the brain has its own specialized surface called cortex. Instead of plants, animals, and ecosystems found on Earth, in cortex you find neuron cell bodies, and synapses, the connections between neurons.

Comparing the brain's cortex and Earth's crust. Image: Monica Oh

A mountain has more surface than a flat area of land. Similarly, cortex is folded, allowing more to fit within the skull. Higher order animals have more folded brains and thus more cortex. More cortex means more neurons, which most researchers think results in greater intelligence.

Different regions of cortex are connected by axons, in a region of the brain called white matter. The brain is about 50% white matter and 50% cortex.

Amy Sterling

Functional maps of cortex reveal that different regions of brain specialize in certain types of information processing. For example, motor cortex transfers intent to move into physical movement and auditory cortex relays hearing to the rest of the brain.

In addition, animals with special abilities tend to have more cortex devoted to it. Consider dogs. They can sniff bacon from seemingly miles away. How? They have relatively 40 times more brain devoted to smell than humans. Even cats have a sense of smell that's about 14 times stronger than ours.

If an animal has amazing vision, chances are it has a high proportion of cortex devoted to vision. Amazing hearing? Auditory cortex. Infrared vision? A totally new part of the brain that isn't present in animals that cannot see in infrared. Next time you're watching a nature show or encountering a cool creature in the wild, think about which specialized functional regions of cortex are prominent based on the animal's special abilities.

Not all cortex is specialized and tied to specific sense. Intelligent animals tend to have relatively more areas of generalized cortex, the most important of which is called prefrontal cortex (PFC). PFC is found behind the forehead and is active during a myriad of complicated activities ranging from introspection to problem solving. Many researchers hypothesize that a sense of self is strongly linked to activity within PFC.

We know a great deal about the brains, yet we are still unable to answer many of the most interesting questions relating the brain to the mind. While the brains of humans, certain apes, mice, and c. elegans are well studied, we know next to nothing about the brains of most animals on Earth. We've learned more about the brain in the past two decades than in all of human history. There has never been a more fruitful time to study the brain. Perhaps future discoveries will come from you!

Daniela Gamba, Seung Lab