An integrated imaging microscope for untethered cortical imaging in freely-moving animals

Imaging in awake, behaving animals is an emerging field that offers the advantage of being able to study physiological processes and structures in a more natural state than what is possible in tissue slices or even in anesthetized animals. To date, most imaging in awake animals has used optical fiber bundles or electrical cables to transfer signals to traditional imaging-system components. However, the fibers or cables tether the animal and greatly limit the kind and duration of animal behavior that can be studied using imaging methods. We present an integrated imaging microscope (IIM) that incorporates all aspects of an imaging system - illumination, optics and photodetection - into a small footprint device, occupying under 4 cm³ and weighing 5.4 g, that can be attached to the skull for imaging the brain in mobile rats. Power supply and image storage sufficient for ~7 hour operation at 15 frames/s was implemented on a backpack weighing 11.5 g. We implemented several optical techniques including reflectance, spectroscopy, speckle and fluorescence with the IIM, imaged vessels down to 15-20 μm in diameter and obtained, to the best of our knowledge, the worlds first cortical images from an untethered, freely-moving rat.