Central nervous correlates of chemical communication in humans

The recording of chemosensory event-related potentials (CSERPs) has been established as an objective method in the assessment of central odor processing in humans. In the present study CSERPs were used to investigate whether human body odor is genetically determined by the major histocompatibility complex (MHC), referred to in humans as the human leukocyte antigen (HLA). The immunological function of the MHC is the discrimination of self/nonself within the immune system. In rodents it has been shown that body odor is significantly influenced by the MHC and that it can be discriminated by members of different species. To create a sufficiently large subject pool, 144 subjects were screened for their HLA class I loci A and B. During the electroencephalography (EEG) session the subjects (n = 40/20 women) were confronted with the body odor (axillary hair) of three different donors. Two donors (d1 and d2) were HLA-similar but had a different HLA type than the third donor (d3) and the perceiving subject. The third donor and the perceiver shared a similar HLA type. Half of the perceivers received odors from donors of the same sex, the other half smelt odors from donors of the opposite sex. In the EEG session subjects were presented with 200 trials. The odors were delivered through a constant flow olfactometer non-synchronously to breathing. The odor of d1 appeared frequently (p = 0.6) whereas the odors of d2 and d3 appeared each at a rate of p = 0.2. During half the trials the subjects were instructed to respond to the odor of d2, during the other half to the odor of d3. The EEG was recorded from Fz, Cz, Pz, F3, P3, F4 and P4 in reference to linked mastoids. First results show that male perceivers show enhanced potentials in response to male donors of a similar HLA type (d3). The CSERP results of the other groups as well as valence and attractiveness ratings will be discussed.