Perception of odors of simple pyrazines by young and elderly subjects: a multidimensional analysis.

Ten simple stimuli from the heterocyclic class of nitrogen chemicals known as pyrazines were arranged in a three-dimensional space by INDSCAL using similarity judgments by 12 young and 11 elderly subjects as input. Odor quality at two intensity levels, moderate and strong, was examined. At both concentrations, pyrazines with the highest intrinsic polarity were arranged separate from unsubstituted pyrazines as well as alkyl pyrazines with a single alkyl moiety or any substitution pattern wherein alkyl groups are geometrically opposite. Use of the pattern recognition procedure ADAPT in conjunction with PREFMAP and canonical correlation procedures pointed to the relationship of three variables to olfactory quality: (1) the presence of oxygen atoms, (2) the environment associated with a substructure of the pyrazines and (3) stimulus concentration. Six of the elderly subjects showed a possible loss in the ability to discriminate among the pyrazines at the moderate intensity level.