Motion-induced transient room tilt illusion in an otherwise healthy subject

Room tilt illusion (RTI) - transient upside-down vision or apparent tilt of the visual scene on its side - has been described in patients with acute l esions of the brainstem, the parieto-occipital region, or the frontal lobe and in patients with epilepsy. Published cases so far have been based on pa tient histories taken after the event. A 31-year-old, otherwise healthy sub ject repeatedly experienced upside-down vision for seconds over a period of about 12 years. To elicit RTI in this subject, we applied various precipit ating stimuli in the pitch, roll, or yaw plane after a period of visual occ lusion. Shutter glasses were used to determine the duration of the illusion and of its reversion. RTI was induced in 65-100% of trials by changes in h ead or body position or by large-field visual motion stimulation following a period of visual occlusion of at least 15 seconds. Angles of tilt were co nfined to 90 degrees or 180 degrees. The direction of tilt was identical to the direction of the preceding head or body motion in the roll plane, but opposite to the direction of visual pattern motion in the roll plane. RTI w as stable for more than one second; then it gradually reverted to normal wi thin six seconds. This reversion occurred with or without the assistance of vision. A mechanism that might explain the experience of this exceptional subject is a transient cortical mismatch of vestibular and visual spatial 3 D-coordinate frames.