How humans think. [Image via Ella Maru Studio & MPI CBS / Doellerlab]

How do humans think? This is one of the most intriguing questions that has captivated neuroscientists for decades. And not long ago, it seemed like something that no one would ever find an answer to.

But, a team at the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) in Leipzig, Germany, and the Kavli Institute for Systems Neuroscience in Trondheim, Norway have come up with a conclusive answer that humans think using the brain’s navigation system. The results of the finding have been published in the journal Science.

With a complex network consisting of a staggering one hundred billion nerve cells, the brain is the most complex organ in the human body. So far we have explored how brain works to help us remember things, take action, feel and experience everything around us, but the navigation system and its involvement in the thinking process had never been studied before.

The brain’s navigation system comprises two active cells: place cells in the hippocampus, and grid cells in the neighboring entorhinal cortex that work hand in hand to help us navigate. But as the researchers has recently revealed, the system does much more than that: it helps us think, too. Their finding also explains why our knowledge are organized in a spatial manner.

Christian Doeller, senior author of the paper, explains that the brain accumulates information such as geographical data, and relationships between objects and experience in so-called cognitive spaces.

Cognitive spaces are actually mental maps in which we stores information gathered from our surroundings. Everything that we come across such as a person or an object has physical properties, and they are arranged along different dimensions in cognitive spaces. Also depending on the magnitude of interest, individuals are stored mentally closer together or further away.

“If I think about cars, I can order them based on their engine power and weight for example,” says Doeller. “We would have racing cars with strong engines and low weights as well as caravans with weak engines and high weight, as well as all combinations in between.”

“We can think about our family and friends in a similar way; for example, on the basis of their height, humor, or income, coding them as tall or short, humorous or humorless, or more or less wealthy.”

Doeller and his team first constructed a theory of human thinking. The theory started with the discoveries of place and grid cells in rodent’s brains, which won the Nobel Prize. These cells were later found to be present in humans, too.

While studying rodent’s brains, the team observed both the cell types showing patterns of activity. Each unique pattern of activity represents the animal’s position in space, for example, while it looks for food. The team then combined the activity of place and grid cells and were able to come up with a mental map of the surroundings as seen by the animal. This information is stored and used for later visits.

Surprisingly, the grid cells in humans were found to exhibit similar activation pattern, too, during navigation through geographical spaces as well as when learning new concepts.

By utilizing the maps of cognitive spaces, humans can tell how similar something new is to something they already know by reactivating the map with regard to existing dimensions.

According to the team, these processes are useful for learning about the new things or events even if  have never experienced them before.

For example, if we have already learned about tigers, lions, leopard but nothing about panther, the position of the panther would be in where we put the other big cats in our cognitive space. So when we encounter with the panther for the first time, we would react according to our knowledge about the concept ‘big cat’ stored in a mental map.

Reference: Navigating cognition: Spatial codes for human thinking (Science)