The helmet head restraint system: a viable solution for resting state fMRI in awake monkeys.

In monkey neuroimaging, head restraint is currently achieved via surgical implants. Eradicating such invasive head restraint from otherwise non-invasive monkey studies could represent a substantial progress in terms of Reduction and Refinement. Two non-invasive helmet-based methods are available but they are used exclusively by the pioneering research groups who designed them.