Alleviating head-mounted weight burden for neural imaging in freely-behaving rodents

The recently developed miniaturized head-mounted two-photon (2P) imaging devices have served as a valuable tool for neuroscientists, enabling real-time functional neural imaging in freely-behaving animals. Although the current 2P fiberscopes and miniscopes are lightweight, the weight of any potential additional accessories inevitably imposes a burden on the animal. Here, we present a buoyancy levitation method to alleviate head-mounted weight burden on mice. By utilizing the buoyance of a helium-filled balloon to counteract the additional weight of up to 7 g, mice' motion behavior remains largely unaffected by the added load. Neuroimage analysis provides new insights into the effects of weight burden on neural activities. This easy-to-implement method offers a platform for studying neural network function in animals, effectively freeing them from the burden of head-mounted weight.