A computer-controlled olfactometer for fMRI and electrophysiological studies of olfaction

Abstract

A design for an inexpensive and reliable olfactometer is presented. The design has several advantages for fMRI and electrophysiology investigators. These advantages include relatively rapid odorant rise times, computer control, multiple odor administration, and no ferrous materials near the subjects. In addition, the device is contamination resistant, and, because the air is neither warmed nor humidified, it is unlikely to become an incubator for bacteria. The olfactometer is constructed of off-the-shelf chromatography parts that require little modification.A variety of instruments have been developed over the past 100 years for the accurate and metered presentation of odors (for a review, see Prah, Sears, & Walker, 1995). Most of these instruments have been developed to meet the demands ofparticular situations or unique experimental settings, with each new need generating changes to existing devices. For instance, Kobal and Hummel (1988) developed an olfactometer with very rapid rise times in order to produce chemosensory event-related potentials. Laing (1986) also produced a unique olfactometer, for behavioral work with odor mixtures, that allowed odors to be introduced in very rapid succession. The advent of fMRI studies of olfactory and chemosensory processes presents a new set of needs, and the olfactometer described here has been developed to meet these needs in a simple and cost-effective manner.The fMRI laboratory presents several important and new demands on an olfactometer. The most obvious and essential is the absence of ferrous metal near the magnet. Ideally, the instrument should have the following features: (1) computer control; (2) effective delivery ofa variety ofodors, in series or randomly; (3) production ofan odor stimulus ofselectable and reliable duration in a constant airstream, without any additional type of ancillary stimulation (e.g., tactile, auditory); (4) resistance to contamination; (5) durability; (6) ease of operation, refilling, and cleaning; and (7) low cost. The olfactometer described here meets these needs and is relatively easy to construct. With the exception ofexcluding ferrous metals,

A comparison of sniff bottle staircase and olfactometer-based threshold tests

“…The designs implemented by Popp et al (2004); Lorig et al (1999) share many similarities, including the method by which odorant dilutions are calculated, as well as the use of multiple successive air streams to ensure odor dilution. In addition, Lorig et al noted that the odor can be delivered to the participant in a variety of ways with little alteration required; in most previous research a face mask has been used, but modification to a sniff port into headspace would be trivial.…”

“…Our olfactometer design is simple and similar to several preexisting olfactometer setups (Davies & Davies, 1999;Johnson & Sobel, 2007;Lorig et al, 1999;Popp et al, 2004). The olfactometer is a "Dravnieks-style" olfactometer ( Fig.…”

A low-cost, MR-compatible olfactometer

“…The issue could be eliminated entirely by maintaining a constant flow through all odorant bottles and switching the resulting output flows, but switching odors directly would introduce a set of new engineering challenges and design complexities, including disposing of the unused odorant in such a manner that it did not come in contact with the subject's nose. Furthermore, many olfactometers employ variable odorant flow (see, e.g., Lorig et al, 1999). …”

“…Vigouroux, Bertrand, Farget, Plailly, and Royet (2005) presented a method for manually delivering odors synchronized to a subject's inhalation in an MR environment. Finally, Lorig, Elmes, Zald, and Pardo (1999) described a sophisticated MR-compatible olfactometer that delivers precise amounts of odorant.…”

Development of a fully automated system for delivering odors in an MRI environment

“…In addition to these requirements, we wanted a system that could be easily and rapidly replicated at a relatively low cost. Although several inexpensive, easy-to-use, and efficient MRI-compatible olfactory stimulators exist (Lorig, Elmes, Zald, & Pardo, 1999;Popp, Sommer, Müller, & Hajak, 2004;Sobel et al, 1997), we wanted to present another system that would constitute a good alternative. The stimulation device we describe here was inspired mainly by the work of Lorig et al Its characteristics make the present device suitable for a wide variety of experimental paradigms.…”