Figure 1.

The two test protocols for testing semicircular canal function. (A) In the HIMPs protocol (the classical test protocol), the person is required to maintain fixation on an earth-fixed target during a small, unpredictable, passive, head turn. Healthy subjects will not make any saccades at all or only small saccades. (B) In the SHIMPs protocol, the head turn is identical but the instructions are different—the person must maintain fixation on a head-fixed target (a spot from a head-mounted laser projected onto the wall in front of the subject). Healthy subjects make large saccades (see text for explanation).