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Curiosity Challenge: How does the brain process information?

How does the brain process information? Jessica, Age 7
How does the brain process information? Jessica, Age 7

Dear Jessica,

Thanks for your question! To think about how the brain processes information, I think we must first consider how our brains gain access to information. Because the brain is confined within our heads and mostly separated from the rest of the world, there must be something external to the brain that communicates information from the outside world.

In fact, this is the precise purpose of our five senses: sight, hearing, touch, taste, and smell. Information comes in the form of patterns of light (images), vibrations of the air (sound), physical touch, and the chemical compounds around us that we taste and smell. Each of these types of information is received by a particular type of nerve cell, called peripheral neurons, in the relevant parts of our bodies. We have these neurons in our eyes, ears, nose, mouth, and underneath our skin, which when activated, send electrical signals to neurons in our brains.Electrical signals are therefore the language of neurons—the way they pass on information to each other.

Electrical signals are therefore the language of neurons—the way they pass on information... Click To Tweet
Diagram showing the “what” and “where” streams in the brain. Signals travel from primary visual areas in the occipital lobe (shown in gray) to the temporal lobe (purple) and the parietal lobe (green). The “what” stream leads to object recognition, while the “where” stream localizes objects in space and recognizes motion.

As an example of how our senses give us information that’s processed by the brain, let’s imagine that you’re playing a game of catch and the ball is coming toward you. To see the ball, neurons in your eyes first take in the light of the scene in front of you, and they do the job of translating that light into an electrical signal. Your neurons act like a wire to pass on signals to the next neuron, and eventually they are sent to the area of your brain that first processes visual information, called the occipital lobe.

At this point, the brain has information about the contours of the object you saw, but it can’t name it or identify its use. From there, the signal gets passed on to two areas of the brain known as the temporal and parietal lobes. The temporal lobe is the site of the “what” information, allowing you to recognize the object you see and identify it as a ball. The parietal lobe on the other hand, is the site of “where” information, telling you where the ball is at each moment in time, and recognizing that it is moving toward you. Once you know that it is a ball, you can connect the idea of the ball with all the ways you have used a ball before, including catching. This all happens very fast, in less a few seconds, to allow you to catch the ball.

The sensory homunculus, showing the space in sensory cortex devoted to sensory input from various parts of the body. The face and hands are overrepresented.

So what happens once the ball touches your hands? There are other sets of sensory neurons in your hands and fingers, underneath your skin, that sense touch. When the ball touches your hands, these neurons are excited and they then send electrical signals to the neurons they are connected to, which are located in our spinal cords. From there, the signal travels up to our brains, to what is called the sensory cortex. The sensory cortex is made up of neurons that get these signals from all over the body, and it is organized so that all the neurons that get information from your hands are together in one place, and from your feet in another place, and so on. This organization results in some parts of the body, like our hands and face, being much more sensitive to touch because they have bigger areas in the sensory cortex. A visual representation of this divvying of sensory cortex real estate is known as the homunculus.

Playing catch is just one example of the way our brains process information—we also use these kinds of systems to hear and talk, to eat and to smell. One of the basic overarching rules of this type of sensory processing is that the first neuron involved, the one that is connected the outside world, has the most information. For example, the neurons in your eye that you use to see the ball coming toward you are also getting information about every person in the background, and every shadow or ray of light around you. But as that neuron signals to each neuron after it, our brain processes this information so we keep only the parts that are relevant to us at any given moment.

For example, our brain won’t keep the information about exactly how sunny it was outside when you were trying to catch the ball, it would only keep the information that helps you separate the ball from the background and see it more clearly. This is also why someone could walk by in the background of your game of catch, and even though the neurons in your eyes took in that information, you might not notice. This is a common theme in how the brain processes information to make it useful to us in our daily lives. It keeps us from getting overloaded and lets us efficiently react to our environments based on what we are paying attention to.

If you want to learn more about this, I would highly recommend watching Episode 2 from Season 1 of the National Geographic series, Brain Games, entitled: “Pay Attention!”

If you want to see this phenomenon in action for yourself, I would also recommend watching The Monkey Business Illusion in the video below.


Nivanthika K. Wimalasena is a second year graduate school student in the Harvard Program in Neuroscience. She is interested in the way sensory neuron activity leads to the perception of pain, and the mechanisms by which these neurons degenerate and regenerate. She is also excited about getting kids involved in science and looks forward to answering more Curiosity Challenge questions! If you have questions, you can reach her at nivanthika.wimalasena@gmail.com.

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