Heimel Group

Alexander Heimel:

Based on behavioural experiments in animals, Nobel Laureates (1973) Niko Tinbergen and Konrad Lorenz posited that instinct is innate, immutable behaviour. When they exposed turkey chicks to cardboard birds ‘flying overhead’, the chicks panicked when the silhouettes were of birds of prey, recognizable by their short necks. But they didn’t respond to birds with a longer neck. Both scientists concluded that the brains of turkey chicks contain an innate template for birds that are a danger to them. ‘It later turned out that these chicks were at a Bavarian farm and had seen numerous geese flying overhead. That was why they weren’t afraid of them,’ Heimel smiles. ‘This was therefore a case of habituation (getting used to regularly recurring stimuli, the simplest form of learning). It IS thus possible for instinctive behaviour to change on the basis of experience.’

Heimel investigates, in mice, in which brain circuits instinctive behaviour is elicited and where habituation takes place. For this he uses a flexible optical fibre which, placed inside the mouse brain, renders brain cells fluorescent when they are active. In this way he can see which brain circuits are at work, for instance when he uses a magnet to move a ball across the non-transparent floor of a mouse cage. Heimel: ‘A mouse immediately jumps to it and wants to catch it, even if it has never seen something like it before. So if something tiny moves, it is the mouse’s instinct to respond in this way. There are cells in the mouse brain that detect the ball, the mouse has no option but to respond and catch the ball. What we are trying to do is to exactly map all those phases.’

Heimel uses the data he gathers to test which brain cells are crucial for instinctive behaviour. Based on these data, he does this by switching certain brain circuits ‘on’ and ‘off’ using the optical fibre. Heimel: ‘Activity that happens simultaneously with running away, such as breathing faster, is not necessary for instinctive behaviour. We need to filter out such activity to find out which brain circuits are important exclusively to instinctive behaviour. That knowledge could put us on the trail of the neural basis of, for instance, instinctive startle responses that are intensified to the extreme, as is the case with PTSD (post-traumatic stress disorder).’

In addition to this research, Heimel is studying how the visual system encodes information. ‘When I see an individual in a new place, and they wear different clothes, my retina still recognizes them – even though the exact image differs from the earlier occasion, and even though they might look like all kinds of other images my brain has filed away. Apparently my visual system creates an abstraction somewhere. But where? And how?’ Here, too, research into the brain activity of mice could provide a solution. The knowledge it provides is not only important for people, but can also help with the – faster – development of computer vision, technology that converts images into information. Examples might be facial and behavioural recognition and interpretation, application in the field of virtual and augmented reality, and improved performance of self-driving cars.