While the animal is navigating, two key cell types become active: the so-called “place cells” of the hippocampus and the “grid cells” of the entorhinal cortex, a brain structure adjacent to the hippocampus. “The function of place cells is to map and then to help recognize space. The grid cells register the regularities of an environment and enable distances and directions to be measured,” explained Doeller. Together with other cell types in the hippocampal system, these form the brain’s navigation system. For the discovery of place cells in 1971 by the British-American neuroscientist John O’Keefe and of grid cells in 2005 by the Norwegian research couple May-Britt and Edvard Moser, the three scientists jointly received the 2014 Nobel Prize in Medicine.

How does the human brain navigate?
The fundamental biological insights gained from animal research are explored in cognitive neuroscience with the human model. Doeller’s own research focuses on the question of how spatial navigation, memory, and higher cognitive processes function in the human brain. The navigation system, Doeller continued, is an elementary building block of higher cognitive functions. This ultimately leads to the great question facing research as to whether there is a navigation system in the human brain that enables us to think.

This is not just about spatial navigation, but about how information is represented in the human brain in general. “As cognitive neuroscientists, we see the representation of information in cognitive maps or spaces as an efficient, biologically plausible principle for the long-term storage of information,” said Doeller and gave the following example: To acquire new knowledge about vehicles, one can map this information in a two-dimensional (knowledge) space and arrange the vehicles within it according to the two dimensions of engine power and weight.

To measure brain activity in humans, cognitive neuroscience does not use invasive techniques as is does with animals, but rather the non-invasive method of magnetic resonance imaging (MRI). “We measure neuronal activity indirectly via blood flow while the subject lies in the scanner and performs a cognitive task. In this way, we can combine a person’s behavior with a simultaneous recording of their brain activity, just as with animal models,” said Doeller in explaining the procedure. Experiments involving spatial navigation make use of computer games in which the subjects navigate in virtual environments. Virtual reality is also used in experiments as a technique for simulating episodes such as everyday experiences.

A contribution to Alzheimer’s research
The hippocampus, as the elementary region in the brain for memory navigation, is affected by neurodegenerative diseases such as Alzheimer’s. In animal models that simulated the disease at the biological level, it was shown that the navigation system functions with less precision. To examine the mechanisms responsible for this in humans as well, Doeller’s research group studied young subjects with an increased genetic risk of developing Alzheimer’s disease. In an MRI comparison with the control group, they showed a reduced grid cell signal. However, this should not be interpreted as a symptom of the disease, but rather as an interesting scientific finding. Work is currently still being carried out to determine whether these approaches could be used for early detection of Alzheimer’s. “A major problem with Alzheimer’s disease is that it is detected too late. And this is where our basic research comes into play,” said Doeller.

Neuroscience and AI
Doeller referred to artificial intelligence (AI) as the research field of the future. Many of the elementary AI models and artificial neural networks are inspired by biological principles. “It is very important to conduct basic research in the field of AI. I see great potential in using AI to gain new fundamental insights not only in biology, physics or materials science, but also in the social sciences,” Doeller emphasized in conclusion.