Releasing the Hounds: Imaging Activity in Neuronal Populations in the Freely Moving Animal
Jason Kerr, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
Exactly how cortical neurons interact within a population to encode sensory input is currently not known, especially during behavior. What is clear is that single neurons do not act in isolation, but rather act in concert within a population (for a review see: Kerr and Denk 2008). It is also clear that any advances in our knowledge about the function of neuronal populations during sensory input will have to be related to the awake behaving animal. The traditional approach to solving these sorts of questions, especially in the sensory input areas of the cortex, is to restrain the animal and present it with a series of simple sensory stimuli. Although this has been extremely instructive and has been the basis of most of our detailed knowledge about the cortex, the problem is trying to place this knowledge back into context of the freely exploring animal.
I will present in vivo optical recording approaches that have single cell resolution and are based around the two-photon excitation principle and are combined with single cell electrophysiology (Greenberg, et al. 2008). Together with fluorescent activity indicators, this approach is able to monitor activity from many neurons simultaneously while the animal is performing behavioral tasks. I will also present data from our head mounted two-photon scanning microscope (Sawinski, et al. 2009) that allows for the recording of neuronal activity from a freely moving animal, when the animal's interaction with the environment is self-determined, which occurs during natural behavior (kyb.tuebingen.mpg.de/press/2009/kerr.html).