Intranasal trigeminal detection of chemical vapors by humans

The majorityof 14 human observers lacking olfactory nerve function detected, by nasal inhalation, over one quarter of 31 chemicals commonly used in olfactory research. No major differences were noted between anosmic observers with and without documented anatomic, genetic, or physiologic etiology. Detected compounds differed significantly from nondetected ones on the basis of a number of chemical properties, including water solubility and molecular weight. Detection thresholds of the anosmics, established by a single staircase procedure, were approximately two log volume concentration steps above those of normals for two compounds examined. Exponents of power functions fitted to magnitude estimates of the anosmics did not differ significantly from those fitted to the estimates of matched normal controls. These data indicate the trigeminal nerve may play an important role in human nasal chemoreception and that effective trigeminal stimulants may be predictable on physicochemical grounds.