Title: Ocular tilt reaction - Wikipedia
Headings: Ocular tilt reaction
Ocular tilt reaction
References

Content: Each anterior semi-circular canals has excitatory projections to the ipsilateral superior rectus muscle and its yoke i.e., the contralateral inferior oblique while simultaneously inhibiting the ipsilateral inferior rectus muscle and its yoke i.e. the contralateral superior oblique. Also, each posterior semi-circular canals has excitatory projections to the ipsilateral superior oblique and its yoke i.e. the contralateral inferior rectus, while simultaneously inhibiting the ipsilateral inferior oblique and its yoke i.e. the contralateral superior rectus. A head tilt causes stimulation of both anterior semi-circular canals and the posterior semi-circular canals resulting in excitation of ipsilateral intorters ( superior oblique and superior rectus) and contralateral extorters ( inferior oblique and inferior rectus) while their antagonists are simultaneously inhibited. The otoliths ( utricle and saccule) probably follow a similar pathway. Normally, a body tilt (along with the initial head tilt) to the right causes a shift of the subjective visual vertical (SVV) to the left resulting in reflex, compensatory orientation of the head to left to realign the SVV to the true vertical. The initial head tilt to right will cause stimulation of the right utricle resulting in excitory signals to pass to the SR and SO (right eye), and IO and IR (left eye). Simultaneously, inhibitory signals pass to their antagonists. The stimulated two intorters (right eye) and the two extorters (left eye) have opposite vertical actions i.e., one is an elevator and the other is a depressor. The opposite vertical actions nearly cancel each other and therefore only a small vertical deviation occurs, whereas their identical torsional actions are additive. In case of any lesion from the utricle to the brainstem, diminished input from the affected vestibular pathway, for example the left vestibular is the same as stimulation of right vestibular pathway, resulting in the erroneous interpretation by the brain that the head is tilted to the right and consequently that the SVV is tilted to the left.