With the aim of using multiphoton imaging in freely moving and behaving animals, we developed in collaboration with Winfried Denk (MPI for Medical Research, Heidelberg) a miniaturized microscope small enough to be carried on the head of a freely moving rat.

This microscope, or fiberscope, has all of the features of a conventional 2-photon microscope, and can accurately measure activity from populations of neurons in the visual cortex of a freely behaving animal for extended periods of time.

We have now added to this the capacity to track the position and orientation of the animals head and simultaneously image the high-speed movements of both eyes during these recordings, and have shown that the range and independence of eye movements in freely moving rats is far greater than previously documented.