The Indirect Path of the VOR

Where does the required tonic input come from?

The tonic command originates via the indirect path through the n. prepositus hypoglossi

This nucleus converts the phasic vestibular input into a tonic signal (in the same way as it does for the phasic command of saccades).

Motoneurons thus normally exhibit the combined input from:
1) a phasic command (which rotates the eye) via the direct path
2) a tonic command (which holds it there) via the indirect path


Copywrite © 1996 Tutis Vilis and Douglas Tweed
Department of Physiology
University of Western Ontario
London Ontario Canada
Updated October 01, 1996

Comments welcome. Email to tvilis@physiology.uwo.ca