Table 4C.
Orienting angles for optimal alignment of a human subject's head for head-on-body “head impulses” with the subject seated upright, for each SSS separately and for functional canal pairs
| Semicircular canal to stimulate | Orienting rotations starting from REASO | Stimulus Rotation should be about an axis that is... | Excite SCC by turning head | ||
|---|---|---|---|---|---|
| Head-on-body rotational head acceleration impulses (“head thrusts”) with subject sitting erect | Left | Horizontal | 18.8° ND about YEarth then 2.2° LED about XEarth | YEarth | Leftward |
| Subject sitting upright and visually fixating a target directly anterior of nose (along +XREID). | Anterior | 16.7° ND about YEarth | In Earth-horizontal plane, 38.0° posterior to +YEarth 38.0° anterior to −YEarth | CCW/ND | |
| For horizontal SCC, it is convenient to deliver head impulses about the ZEarth axis, just as for rotary chair test. | Posterior | 21.3° ND about YEarth | In Earth-horizontal plane, 48.2° anterior to +YEarth 48.2° posterior to −YEarth | CCW/NU | |
| For anterior and posterior SCC, limited neck range of motion prevents delivery of head thrust rotation stimuli when SCC axis is aligned with ZEarth and body is sitting upright. Instead, reorient head pitch-nose-down to bring anterior or posterior SCC axis of interest into Earth-horizontal plane, then deliver rotational stimuli about that SCC axis. | Right | Horizontal | 18.8° ND about YEarth then 2.2° RED about XEarth | ZEarth | Rightward |
| Anterior | 16.7° ND about YEarth | In Earth-horizontal plane, 38.0° posterior to +YEarth 38.0° anterior to −YEarth | CCW/ND | ||
| Posterior | 21.3° ND about YEarth | In Earth-horizontal plane, 48.2° posterior to +YEarth 48.2° anterior to −YEarth | CW/NU | ||
| Rotation directions are from subject's point of view, so counterclockwise (CCW) and leftward (L) rotations move the forehead toward the left ear. ND = nose down. NU = nose up. LED = left-ear-down. RED = right-ear-down. REASO defined in Table 4A. Axes illustrated in Figures 3 and 4. | Canal Pair | LH RH | 18.8° ND about YEarth | ZEarth | See side-specific directions above |
| LA RP | 19.2° ND about YEarth | In Earth-horizontal plane, 43.0° posterior to +YEarth 43.0° anterior to −YEarth | |||
| RA LP | 19.2° ND about YEarth | In Earth-horizontal plane, 43.0° anterior to +YEarth 43.0° posterior to −YEarth | |||