Individual odors

Breast-fed neonates themselves distinguish breast (Macfarlane, 1975 Russell, 1976 Schaal etal, 1980) and axillary (Cernoch and Porter, 1985) odors of their mother from the same body region odors of other lactating women. 

Male red-backed salamanders Plethodon cinereus) in Petri dishes were given a choice between own feces and those of another male. They preferred their own. The same was true for washes from the cloacal glands (Simon and Madison, 1984). While this may represent discrimination of own and other, rather than true individual recognition, another experiment showed 

In primates, lemurs distinguish and remember individual odors. In L.ful-ves the anogenital scent mark of an evicted individual was still recognized (i.e., scent-marked) 10 months after the eviction (Fornasieri and Roeder, 1992). 

Individual recognition can be important for selecting and correctly recognizing mates, reducing aggression, incest avoidance, and sexual re-arousal, in the Coolidge effect (named after an anecdote about a US President and refers to increased sexual arousal with a new mating partner) (Dewsbury, 1981). 

Discrimination of individual odors may depend on the sex of the odor donor. In the Virginia opossum (D. virginiana), females distinguish individual female, but not male odors (Holmes, 1992). 

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Johnston R.E. and Peng M. (2000). The vomeronasal organ is involved in discrimination of individual odors by males but not by females in golden hamsters. Physiol Behav 70, 537-549. 

Petrulis A. and Johnston R. (1999). Lesions centered on the medial amygdala impair scent-marking and sex-odor recognition, but spare discrimination of individual odors in female golden hamsters. Behav Neurosci 113, 345-357. 

Petrulis A., Peng M. and Johnston R.E. (1999). Effects of vomeronasal organ removal on individual odor discrimination, sex-odor preference, and scent marking by female hamsters. Physiol Behav 66, 73-83. 

Heth, G., Todrank, J. and Johnston, R.E. (1999) Similarity in the qualities of individual odors among kin and species in Turkish (Mesocricetus brandti) and golden (Mesocricetus auratus) hamsters. J. Comp. Psychol. 113, 321-326. 

Halpin, Z.T. (1980) Individual odors and individual recognition Review and commentary. Biol. Behav. 5, 233-243... 

Halpin, Z.T. (1986) Individual odors among mammals Origins and functions. Adv. Stud. Behav. 16, 39-70... 

Schaal, B. and Marlier. L. (1998) Maternal and paternal perception of individual odor signatures in human amniotic fluid - potential role in early bonding Biol. Neonate 74, 266-273. 

By convention the individual odor threshold is that concentration which is just perceived by the subject in 50% of the cases in which it is presented to him. The group threshold is the concentration that is just perceived by 50% of the panel members. 

Female laboratory rats seem to depend upon an intact vaginal bacterial flora to be olfactorily attractive to males. When given a choice in a four-arm maze, adult males spend more time with an untreated estrous female than with one whose vaginal bacteria had been killed by daily injections of an antibiotic (Merkx etal., 1988). Generally speaking, individual odors of rats have microbial, genetic, and dietary components (Schellink and Brown, 2000). 

In the rat and other rodents, individual odors probably reflect genetic differences. Laboratory rats can distinguish individuals. They discriminate between two intact males, two castrated males, two estrous/proestrous females, two diestrous/metestrous females, or two ovariectomized females. Urine odors differ individually despite differences in the levels of gonadal hormones. Individual recognition may be independent of reproductive state or social status, even though hormone-influenced body odors may be used for individual recognition (Brown, 1988). 

In the rat, the major histocompatibility complex (MHC) is responsible for individual odors (Brown etal., 1987a,b). Genetic differences in the JA region actually result in different urine odors (Singh etal., 1987). 

A species may scent mark in two different ways that convey different messages. In the stoat, M. erminea, body rubbing is correlated with threat behavior, while the anal drag permeates an area with an individual odor (Erlinge etal., 1982). 

Odor types distinctive of H2b and Hdh genotypes already appear in the urine of 1-day-old mouse pups (Yamazaki et ah, 1992a). At that age, the normal intestinal bacterial flora is not yet present and hence is not necessary for the odor (Yamazaki et ah, 1992b). In addition to MHC, gene(s) on the X and Y chromosomes and other autosomal genes contribute to individual odors (Yamazaki etal, 1986,1990). 

Most and Bruckner (1936) found human tracks to be complex. A track contains a human species odor and an individual odor, both extruded through boots, but also the odors of crushed plants, disturbed soil, and leather or other shoe material. Dogs still tracked correctly after removal of one or several of these components. To separate the track components, the authors built a chair lift and a track wheel (Fig. 13.5). The rim of the metal wheel (approximately 2m in diameter) carried raised replicas of shoes at stride intervals. Pulled over the terrain, the wheel makes a track of crushed plants and disturbed soil without human scent. The lift consists of a chair suspended on a steel cable about 1.5 m above the ground. Although a person riding this chair leaves no foot imprints or disturbed soil, he/she still sheds odorous rafts of skin cells. A trained dog uses one or the other of these track components, as terrain and surface change. 

Brown, R. E. (1988). Individual odors of rats are discriminable independently of changes in gonadal hormone levels. Physiology and Behavior 43,359-364. 

Individual odors among mammals origins and functions. Advances in the Study of Behavior 16,39-70. 

At first glance, labeled-line coding of olfactory signals may seem in contrast to the ensemble or across-fiber code (Shepherd, 1985) where complex mixtures of odorants or even individual odorant components are perceived as patterns of activity across an ensemble of neurons and AL glomeruli. However, recent experiments examining odor coding of individual ORNs in Drosophila and mammalian olfactory systems demonstrate that individual ORNs are capable of a wide spectrum of responses. In the fly, a particular odor can excite one neuron while inhibiting another, and a particular neuron can be excited by one odor and... 

Tenacity refers to the long-term effectiveness of the fragrance in the perfumed product (as in a soap 1 or an extended action room freshener) or on the surface to which the product has been applied, for example, upon the skin after use of a toilet soap. In former days it was believed that tenacity depende upon the use of so-called fixatives (evaporation-retarding agents) in composing a perfume, today the opinion pervails that it is simply the resultant of the tenacity of the individual odorants used (Jellinek 1978). 

In the normal applications of perfumes, concentrations come into play that lie far above the threshold values. Nevertheless, when used in conjunction with vapor pressure data, the threshold values of individual odorants can give the perfumer helpful information about their performance. Substances with low threshold values are generally more potent in odor than substances with comparable vapor pressure (volatility) and higher thresholds. 

A finished packaging material for a specific food, e.g. a roll of printed laminate film, often possesses a certain individual odor. Even though from a food regulatory view only the transfer of odor substances to the food is important and not the individ-... 

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