Steven Novella writes:

Have you ever been in a semi-familiar location but couldn’t quite place where you were, then suddenly the landmarks line up and you know where you are? This might happen when entering a familiar location from an unusual direction, for example. Also (a seemingly unrelated question), when you visualize abstract ideas, do you arrange them physically. For example, do you visualize time (like days, weeks, months, years), and if so is there a particular physical relationship by which you mentally organize the progress of time?

Scientists from the Max Planck Institute for Human Cognitive and Brain Sciences (MPI CBS) and the Kavli Institute for Systems Neuroscience in Trondheim, Norway have published a paper in which they propose these two mental phenomena are directly related. One of the scientists, Edvard I. Moser, won the 2014 Nobel Prize for some of this work.

For background, researchers discovered that there are a type of neuron called place cells in the hippocampus (specifically area CA1) that store the memory for specific locations. When you are in a familiar location, a unique pattern of place cells will light up. Further, there is a second type of cell called grid neurons, which are arranged in a hexagonal pattern in the nearby entorhinal cortex. These grid cells light up in sequence as you move through your physical space – the physical arrangement of the grid neurons map to the physical arrangement of your environment.

This is an elegant system – your brain basically has a movable grid map, the grid keeps track of your local navigation, while the place cells keep track of where the map is.

This is also not the only example of so-called “somatotopic mapping” in the brain, where the physical location of neurons maps to their function. The other obvious example is the primary visual cortex. There the arrangement of neurons maps to the image itself, like a bitmap built of pixels, with each pixel being a neuron.

This kind of physical mapping is easy to understand, but now here is where the new paper comes in and where things get interesting. The authors propose that we navigate our abstract thoughts using the same neurons as for navigating physical space. [Continue reading…]