TRIGEMINAL AND OLFACTORY SENSITIVITY - COMPARISON OF MODALITIES AND METHODS OF MEASUREMENT

Objective: The principal objective was to chart sensitivity for human nasal irritation by alternative psychophysical methods, namely, a comm on detection procedure versus a nasal lateralization procedure that re quired the subject to indicate whether a vapor had stimulated the left or right nostril. This objective relates to the broader issues as to (a) whether subjects with normal olfaction (normosmics) can yield, thr ough novel methodology, an index of sensitivity to nasal irritation co mparable with that obtained from subjects without olfaction (anosmics) and (b) whether both types of subjects have similar irritation sensit ivity in general. This study sought to gauge interconvertability both between types of subjects and between modes of stimulus presentation f or irritative and, where appropriate, olfactory stimulation. Methods: Static dilution series of four M-aliphatic alcohols, chosen to represe nt volatile organic compounds (VOCs), provided the source of calibrate d olfactory and irritative vapors emitted from their squeezable contai ners into the nose or eye either by a mechanical device or by hand. St andard psychophysical methodology (forced-choice; ascending strength o f stimulation) served to chart detection thresholds for irritation and odor and an analogous procedure served to chart the threshold for loc alization of stimulation. Results. Within the limits of resolution, de tection thresholds and nasal localization thresholds yielded comparabl e indices of the potency of the VOCs to evoke nasal irritation. The th resholds agreed well with those for detection of eye irritation, thoug h only the eyes proved to be capable of detecting irritation from 1-oc tanol. The method of emitting the stimulus had little material effect on measures of either irritative or olfactory detection. Conclusions: The threshold for nasal localization offers a suitable way to measure nasal irritation in normosmic persons. Olfactory stimulation does not interfere with the measure since subjects cannot localize on that basi s. Anosmic and normosmic persons have comparable sensitivity to nasal and ocular irritation. If anosmic persons have any lower sensitivity, as sometimes claimed, it would seem to have only trivial consequences for estimates of the irritative potency of VOCs.