A novel MR-compatible device for providing forces to the human finger during functional neuroimaging studies

Many motor learning experiments involve subjects performing a task while experiencing external force perturbations. However, it is difficult to transfer these tasks to functional magnetic resonance imaging (fMRI) studies, and much of the technology that currently exists to facilitate this is expensive to produce and difficult to use. Here, we report on the design and construction of a novel device (the 'force coil') that is simple and inexpensive, and that uses the static magnetic field inside the scanner to provide forces to the human finger. The coil incorporates a potentiometer in the base to allow the recording of angular position. To test whether the magnetic field generated by the current flowing through the coil would interfere with the functional images collected, we compared images from a phantom during the use of the coil at arm's length in a 7T magnet. There was no noticeable interference from the coil at the levels of current used in this experiment, which produced about 10 N of force in a 7T scanner. In conclusion, the force coil is a cheap, easy to operate device which provides forces to the finger inside the scanner without affecting image quality. Designs based on this principle are likely to prove useful in studies of motor learning using fMRI.