Fig. 2.

Motor responses after vestibular stimulation recorded in in vitro preparations. (A) Electroneurogram of a cervical ventral root (cVR) activity of a preparation from a P5 opossum before and after mechanical stimulation of the sensory vestibular organs (see text for details). The start of the stimulation (‘Stim’, vertical dashed line) is indicated by an artefact generated by a pedal. The dashed squares delineate approximately the areas used to estimate the respective amplitudes of the baseline (‘10 s′) and the response (‘2 s′). Graph in inset: four specimens were tested before (Intact) and after vestibulochlear and facial nerves sectioning (Section), the mean amplitude of the responses was 59.8 ± 13.7% over the baseline before the section and 1.0 ± 1.2% after (* p = 0.0286, Mann-Withney non parametric t-test). (B,C) Electromyograms of triceps brachii muscles activity before and after head elevation of preparations at P11 (B) and P12 (C1,C2). The start of the elevation is indicated by a vertical dashed line (‘Stim’). Head elevations did not induced motor response in most of the trials (B). However, in a few cases, bursts of activity could be recorded following stimulation (C1), but similar bursts were observed after complete section of the vestibulochlear (nVIII) and facial (nVII) nerves (C2).