Sniffing longer rather than stronger to maintain olfactory detection threshold.
Air flow-rate is usually higher in one nostril in comparison to the other. Also, within bounds, higher nasal flow-rate improves odorant detection. It follows from the above that odorant detection should be better in the nostril with higher flow-rate in comparison to the nostril with lower flow-rate. Paradoxically, previous research has shown that odorant detection thresholds are equal for the high and low flow-rate nostrils. Here we resolve this apparent paradox by showing that when detecting through the nostril with lower air flow-rate, humans sniffed longer than when detecting through the nostril with higher air flow-rate, thus equalizing performance between the nostrils. When this compensatory mechanism was blocked, a pronounced advantage in odorant detection was seen for the nostril with higher air flow-rate over the nostril with lower air flow-rate. Finally, we show that normal birhinal sniff duration may enable only one nostril to reach optimal threshold. This finding implies that during each sniff, each nostril conveys to the brain a slightly different image of the olfactory world. It remains to be shown how the brain combines these images into a single olfactory percept.
Sobel
N
N
Program in Neuroscience, Stanford University, Stanford, CA 94305, USA. nsobel@leland.stanford.edu
Khan
R M
RM
Hartley
C A
CA
Sullivan
E V
EV
Gabrieli
J D
JD
D000328:Adult; D002755:Choice Behavior / Q000502:physiology; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D009296:Nasal Cavity / Q000502:physiology*; D012123:Pulmonary Ventilation; D012684:Sensory Thresholds / Q000502:physiology*; D012903:Smell / Q000502:physiology*; D013997:Time Factors