Accounting for Subjectivity in Experimental Research on Human Olfaction.

Although olfaction is a modality with great interindividual perceptual disparities, its subjective dimension has been let aside in modern research, in line with the overall neglect of consciousness in experimental psychology. However, following the renewed interest for the neural bases of consciousness, some methodological leads have been proposed to include subjectivity in experimental protocols. Here, we argue that adapting such methods to the field of olfaction will allow to rigorously acquire subjective reports, and we present several ways to do so. This will improve the understanding of diversity in odor perception and its underlying neural mechanisms.

Individual Differences as a Key Factor to Uncover the Neural Underpinnings of Hedonic and Social Functions of Human Olfaction: Current Findings from PET and fMRI Studies and Future Considerations.

The hedonic and social dimensions of olfactory perception are characterized by a great diversity across people. Whereas the cerebral processing underlying these aspects of odor perception have been widely explored in the last decades, very few brain imaging studies considered individual differences. This lack of consideration weakens the current models in the field, where the paradigm of universality is the norm. The present review is aimed at examining this issue. Through a synthetic summary, we will first present past studies suggesting that (1) hedonics are represented consistently throughout the olfactory system from primary to secondary areas, with a progressive cognitive modulation and integration with other senses, (2) social dimension of odors may be represented in a distinct pathway involving social and attentional networks. In a second, and more critical part, we will highlight the importance of individual differences for the cerebral study of human olfaction.

Is the loose anagen hair syndrome a keratin disorder? A clinical and molecular study.

OBJECTIVES: To report the clinical features of the loose anagen hair syndrome and to test the hypothesis that the typical gap between the hair and the inner root sheath may result from hereditary defects in the inner root sheath or the apposed companion layer. DESIGN: Case series. SETTING: A pediatric dermatology unit (referral center). PATIENTS: A consecutive sample of 17 children (13 girls). For 9 of them and their first-degree relatives, molecular analyses were performed in the K6HF gene with 50 appropriate controls. INTERVENTION: Minoxidil therapy (5% lotion) in 11 patients for 1 to 12 months. MAIN OUTCOME MEASURES: Clinical and follow-up features and determination of mutations in the K6HF gene. RESULTS: Most patients had easily pluckable hair with no sign of scalp inflammation or scarring. Ten patients seldom cut their hair, and 4 had unmanageable hair. One patient had hypodontia. Two patients had an additional clinical phenotype of diffuse partial woolly hair. The family history was positive for loose anagen hair syndrome in 5 patients. Marked improvement was noted after treatment with 5% minoxidil lotion in 7 of the 11 patients treated. Polymerase chain reaction analysis of the gene segments encoding the alpha-helical 1A and 2B subdomains of K6hf, the type II cytokeratin exclusively expressed in the companion layer, was performed in 9 families. In 3 of these 9 families, a heterozygous glutamic acid and lysine mutation, E337K, was identified in the L2 linker region of K6HF. CONCLUSIONS: Diffuse partial woolly hair can be associated with loose anagen hair syndrome. A keratin mutation, E337K in K6HF, was possibly causative in 3 of the 9 families studied. Another keratin, and possibly the type I partner of K6hf, could be responsible for loose anagen hair syndrome in other patients, or the gene involved may be a minor gene.