Acute neurocognitive and postural effects of Galvanic Vestibular Stimulation

Previous studies showed acute transient neurocognitive and postural stability
effects of torso and head movements within the static magnetic stray field of a
1.5 T, 3 T and 7 T MRI scanners. These effects probably arise due to induced
electrical currents that are generated during such movements. Surgeons and
radiologists working close to MRI systems need to maintain a high level of
accuracy in neurocognitive and postural performance. Therefore, understanding
of the mechanisms of the observed acute effects is highly relevant for the
development of appropriate safety procedures in practice. We intend to further
investigate the biological mechanisms involved by investigating the potential
role of the vestibular system in evoking the observed acute effects.

The main objective of this study is to gain more insight into the possible role
of the vestibular system in the observed acute effects on neurocognitive and
postural stability due to movement in the static magnetic stray fields of MRI
scanners. In order to achieve this objective we will compare our earlier
reported neurocognitive and postural effects of exposure to movements in the
static magnetic fields near MRI scanners with effects of exposure to Galvanic
Vestibular Stimulation (GVS), a known procedure which directly stimulates the
vestibular system.

Single blind randomised crossover design

Subjects will be exposed to two experimental conditions; a sham condition and
an exposure condition with ~20 seconds of continuous GVS at 0.7 mA before each
single test within the test battery. Simultaneous to GVS stimulation,
standardised head movement will be made to have similar sensory input between
this and the previous MRI-experiment.

First a training session is administered (to explain the procedure and reduce
practice effects) followed after a 15 minutes break by the two exposure
sessions in random order. The visit will take 4 hours in total; one hour for
each session and an hour break in between the two test sessions. Before and
after each test session a short questionnaire will be completed. If potential
short-term effects occur, such as vertigo and nausea, they are expected to last
for a few minutes. No long-term effects of the GVS exposure are known. A
travelling allowance and a financial gift voucher of sixty euro*s for the
completed experiment will be provided.