Smell Threshold as a Test of Central Nervous Function

Abstract

In a study of quantitative olfactometry significant between- and within-subjects variation in smell threshold have been confirmed, and not eliminated by certain modifications in the method of measurement. No consistent diurnal variation in threshold was detected, nor did it bear a significant relationship to ingestion of food. An appetite-suppressant agent containing phenmetrazine theoclate 30 mg produced a significant decrease in threshold. No significant change occurred after administration of dexamphetamine sulphate 10 mg. There was no evidence that olfactory acuity was depressed by these agents. The second determination of a pair was significantly higher than the first, and this phenomenon was not modified by phenmetrazine or dexamphetamine. No significant difference was detected between ascending and descending thresholds. No correlation was found between simultaneous measurements of smell threshold and critical flicker fusion frequency. The extent of variability of smell threshold both between and within subjects severely limits its value as a test of central nervous function. Strict statistical control must be applied to experimental results in order to obtain a true interpretation of their significance.