Humans think using their brain's navigation system: Researchers combine individual threads of evidence to form a theory of human thinking.
It is one of the most fundamental questions in neuroscience: How do humans think? Until recently, we seemed far from a conclusive answer. However, scientists from 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, offer a new proposal in the current issue of the journal Science, Humans think using their brain's navigation system.
When we navigate our environment, two important cell types are active in our brain. Place cells in the hippocampus and grid cells in the neighboring entorhinal cortex form a circuit that allows orientation and navigation. The team of scientists suggests that our inner navigation system does much more. They propose that this system is also key to 'thinking', explaining why our knowledge seems to be organized in a spatial fashion.
The term 'cognitive spaces' refers to mental maps in which we arrange our experience
Everything that we encounter has physical properties, whether a person or an object, and can therefore be arranged along different dimensions.
A Theory of Human Thinking
In their proposal, the team combine individual threads of evidence to form a theory of human thinking. The theory begins with the Nobel Prize-winning discoveries of place and grid cells in rodents' brains, which were subsequently shown to exist in humans. Both cell types show patterns of activity representing the animal's position in space, for example, while it forages for food. Each position in space is represented by a unique pattern of activity. Together, the activity of place and grid cells allows the formation of a mental map of the surroundings, which is stored and reactivated during later visits.
The very regular activation pattern of grid cells can also be observed in humans, but importantly, not only during navigation through geographical spaces
Grids cells are also active when learning new concepts, as shown by a study from 2016. In that study, volunteers learned to associate pictures of birds, which only varied in the length of their necks and legs, with different symbols, such as a tree or a bell. A bird with a long neck and short legs was associated with the tree whereas a bird with a short neck and long legs belonged to the bell. Thus, a specific combination of bodily features came to be represented by a symbol.
In a subsequent memory test, performed in a brain scanner, volunteers indicated whether various birds were associated with one of the symbols. Interestingly, the entorhinal cortex was activated, in much the same way as it is during navigation, providing a coordinate system for our thoughts.