Improving the Assessment of Trigeminal Sensitivity: a Pilot Study

The trigeminal system is a chemosensory system, next to smell and taste, allowing intranasal sensations such as freshness, spiciness, etc. The lateralization task is used to measure trigeminal sensitivity and consists in identifying the nostril stimulated by an odorous substance in a two-alternative forced-choice procedure. However, when performed in the standard method, this task takes almost 25 to 30 min to administer and only gives access to few information. The aim of this pilot study was to compare two alternative methods of administering the lateralization task with the standard method in a group of 53 participants (41.6 years; 32 women). Specifically, we compared (1) the standard method of 40 constant stimuli with a duration of 500 ms, (2) a short version of 20 variable stimuli ranging from 200 to 600 ms (different duration method—DD), and (3) an automatic adaptive staircase method where the test adjusts the duration of stimulation according to the participant’s responses (adaptive duration method—AD). Based on the number of correct answers and the thresholds obtained with the automatic staircase method, the average scores for the two alternative methods correlate with the score at the standard method. In addition, both alternative methods are able to discriminate between participants with a high sensitivity and those with a lower sensitivity. Finally, the DD method is significantly shorter in terms of administration time than the other two methods. This pilot study presents two novel methods to evaluate trigeminal sensitivity which each have a specific superiority over the established technique. The DD method cuts testing time in half whereas the AD method provides threshold estimates for individual nostrils.