iHELMET: A 3D-printing solution for safe endoscopic Ca²⁺ recording in social neuroscience

In vivo calcium imaging using a microendoscope is a state-of-the-art technique to study the cellular activity inside the brain of freely moving animals such as mice or rats. A problem that can arise in social behaviour tests in rats, or similar size rodents, is that one animal interferes with or may even damage the miniature endoscopic camera attached to the second animal.

We outline an inexpensive, lightweight, 3D-printed protector (iHELMET) that surrounds but is not in physical contact with the camera, together with details of its design and construction.

Using a simple design, we demonstrate successful protection of the endoscope and recording in a social situation such as the social dominance tube test.

The helmet's 3D-printed dimensions can be readily adjusted to work with various micro-endoscopes, which may be more difficult for the only other system of which we are aware.

In addition to camera protection, features of the design aid camera stability, helping to secure more optimal imaging of calcium transients in specific regions of interest during long recording sessions.