One nostril knows what the other learns

Abstract

Before exposure, the experimental group (Fig. 1a) showed 25% accuracy (s.d. 11%), which is not significantly different from 33% chance (binomial from chance: Pǃ0.9). Exposure for 21 days doubled the androstenone-detection accuracy in both the exposed nostril (from 25% to 55%, change from baseline: t(11)ǃ3.3, P<0.007; binomial from chance: P<0.002) and the unexposed nostril (from 25% to 49%, change from baseline: t(11)ǃ2.3, P<0.04; binomial from chance: P<0.02). There was no significant difference in the extent of improvement between the exposed and unexposed nostrils (t(11)ǃ0.4, Pǃ0.7).We screened a further 50 subjects to obtain 12 more non-detectors (9 female) for a control study (Fig. 1b) in which we tested for confounding possibilities: first, subjects were initially selected for nondetection, and thus their performance could either remain the same or improve, but not deteriorate (a 'floor effect'); second, even a minute leak in the block may have enabled the blocked nostril to learn; third, participation in olfactory testing may improve performance over time. The control study was identical to the experimental, except that both nostrils were blocked.Control subjects (Fig. 1b) did not differ from the experimental group at baseline (mean accuracy at baseline: experimental group, 25%, s.d. 11; control group, 27%, s.d. 11, t(22)ǃ0.44, Pǃ0.7), and remained at chance detection after 21 days of exposure (change from baseline: t(11)ǃ1.6, Pǃ0.14; binomial from chance: Pǃ0.4). The difference between the two groups after exposure (mean accuracy after 21 days, average for both nostrils) was 52% (s.d. 20) in the experimental group and 35% in the control group (s.d. 14; t(22)ǃ2.3, P<0.03), negating possible confounding factors.We exploited the paired anatomy of the olfactory system 5,6 to demonstrate that the plasticity that underpins the emergence of androstenone detection originates in the central components of the olfactory system. These components may be likened to pattern recognition, which occurs at the olfactory bulbs or in primary olfactory cortex -a substrate that shares information from both nostrils 7 and is optimized for olfactory learning 8-10 . We do not rule out a contribution to plasticity from the peripheral components of the olfactory system 11,12 -peripheral receptors may be induced in the unexposed nostril in response to a central signal (direct or hormonal, for example). It remains to be determined how central and peripheral mechanisms could interact to maximize plasticity in the olfactory system.

Brain response to putative pheromones in lesbian women

“…In addition, none of our subjects reported sexual arousal. Another tentative explanation is that the observed activation with AND in HeW reflected an acquired sensitization to its stimuli in the hypothalamus or its centrifugal networks due to the repeated exposure to men through life sexual experience (38). However, sensitization can be acquired to several odorants and more easily in women (39).…”

Brain response to putative pheromones in homosexual men

“…Alternatively, it could reflect an acquired sensitization to AND stimuli in the hypothalamus or its centrifugal networks, due to repeated sexual exposure to men (35). A third possibility is that HeW and HoM associated AND with sex, whereas HeM made a similar association with EST.…”

Repetitive Olfactory Exposure to the Biologically Significant Steroid Androstadienone Causes a Hedonic Shift and Gender Dimorphic Changes in Olfactory-Evoked Potentials

“…First, Yee and Wysocki (2001) found that olfactory nerve transaction in mice before repetitive androstenone exposure did not prevent the process of exposure-induced sensitization, strongly implicating the olfactory epithelium in the changes. Secondly, Mainland et al (2002), by repetitively exposing only one nostril to androstenone and demonstrating enhanced sensitivity when stimulating the contralateral nostril, proposed that the induced detection originated in central components of the olfactory system, although they did not rule out a contribution from the plasticity of peripheral components (ie the olfactory epithelium). The third study, by Wang et al (2004a), demonstrated that the electro-olfactogram (EOG) in response to androstenone stimulation, increased following repetitive exposure to androstenone, supporting the notion of peripheral olfactory plasticity.…”