Evidence for peripheral plasticity in human odour response.

Of those people who are anosmic to androstenone, a proportion can acquire sensitivity to it by repeated exposure and even those who are able to smell it can lower their threshold with this treatment. Using olfactory threshold testing, intranasal electrophysiology and EEG we show for the first time that: (1) the subjects' detection threshold is proportional to the amplitude of the olfactory evoked potential (EOG) recorded inside the nose; (2) the EOG amplitude is correlated with the amplitude of the olfactory event-related potential (OERP) recorded on the scalp; and (3) with repetitive exposure, human subjects acquire a reduced threshold for androstenone and, as they do so, their EOG and OERP increase. These observations support the existence of odourant-specific plasticity in the peripheral olfactory system.