Olfactory function in psychotic disorders: Insights from neuroimaging studies

Table 1 Description of the olfactory methods used to examine different olfactory domains

Olfactory domain	Methods by which this domain is assessed
Passive smelling	Odorant is presented passively to the subject. Imaging done without response or overt cognitive appreciation
Olfactory detection	Similar to passive smelling, however, the subject must press a button to signal the onset of the odorant perception
Odour “sniffing”	Subjects are given instructions to inhale the odorant during presentation
Olfactory intensity	Rating the odorant as to its perceived strength. Can be done by a button press (Is the odour “strong”?)
	Intensity may be assessed by ratings of odorants (e.g., VAS) outside of the scanner and presenting odours that have been rated on opposite ends of the continuum (very strong vs very weak)
Olfactory familiarity	Recollect prior exposure without the exact autobiographical context and also without naming. Button press if odour is “familiar”
Olfactory hedonics (valence)	The determination of pleasantness of the odorant.
	Button press to rate whether an odorant is pleasant
	Pleasant/Unpleasant odorant rated (e.g., VAS) outside of the scanner and presenting odours that have been rated on opposite ends of the continuum (very unpleasant to very pleasant)
Olfactory identification	Correct identification- those items that are correctly labeled vs those for which label is incorrect
	Olfactory identification test score used to capture most impaired, compared with normal sense of smell
	Forced choice odour naming during scanning