[Pilot study: Determination of the subjective trunk vertical in upright head position]

Consensus has been established that the subjective vertical (SV) is a result of multimodal sensory integration. In order to be able to calculate the vestibulocervical sensory competence for the SV, the isolated subjective trunk vertical axis (STV) was measured under conditions of vertical head fixation.

Young, healthy volunteers (n = 49) were compared to older, healthy volunteers (n = 50) on a three-dimensionally deflectable (tilt, torsion, pitch) trunk excursion chair in which the volunteer's head remains in an upright position. Another young, healthy group was divided into a placebo (n = 27) and a monophasic cervical transcutaneous electrical nerve stimulation (C-TENS; n = 22) group to examine verticality perception.

In the STV after trunk pitch, age was a significant variable (p = 0.021). The older, healthy group of subjects missed the physical vertical by an average of 1.8° more than the younger group. Only the placebo group showed an average improvement in STV of 4.3° after torsion.

Apart from the macular organs the vestibulocervical sensory afference is involved in finding the trunk vertical. A difference in age to the disadvantage of the older healthy subjects was observed, as well as a lack of learning success after applied C‑TENS. The presented pilot study was able to confirm that a correct vertical trunk sensation is caused by vestibulocervical sensory afference in upright head position.