New determinants of olfactory habituation

Abstract

Habituation is a filter that optimizes the processing of information by our brain in all sensory modalities. It results in an unconscious reduced responsiveness to continuous or repetitive stimulation. In olfaction, the main question is whether habituation works the same way for any odorant or whether we habituate differently to each odorant? In particular, whether chemical, physical or perceptual cues can limit or increase habituation. To test this, the odour intensity of 32 odorants differing in physicochemical characteristics was rated by 58 participants continuously during 120s. Each odorant was delivered at a constant concentration. Results showed odorants differed significantly in habituation, highlighting the multifactoriality of habituation. Additionally habituation was predicted from 15 physico-chemical and perceptual characteristics of the odorants. The analysis highlighted the importance of trigeminality which is highly correlated to intensity and pleasantness. The vapour pressure, the molecular weight, the Odor Activity Value (OAV) and the number of double bonds mostly contributed to the modulation of habituation. Moreover, length of the carbon chain, number of conformers and hydrophobicity contributed to a lesser extent to the modulation of habituation. These results highlight new principles involved in the fundamental process of habituation, notably trigeminality and the physicochemical characteristics associated.

Acute regulation of habituation learning via posttranslational palmitoylation

“…Habituation is an evolutionarily conserved non-associative form of learning characterized by a response decrement to repeated stimuli. One of the simplest forms of learning, habituation is defined by ten behavioral characteristics 1,2 , and has been associated with a wide range of behaviors and physiological responses including feeding and drug seeking [3][4][5] , neuroendocrine responses to stress 6 , and mechanosensory 7,8 , olfactory 9 and acoustic startle responses 10 . Moreover, because habituation enables animals to focus selectively on relevant stimuli, it is thought to be a prerequisite for more complex forms of learning 2 .…”

Molecularly diverse odors advance olfactory threshold testing

“…Molecular complexity of an odorant has been found to positively affect psychophysical ratings (Keller & Vosshall, ) but threshold testing addresses a sensation that is typically difficult to describe, hence we find it difficult to explain differences in olfactory sensitivity toward Anethole and Citral with psychophysical sensations of pleasantness. We speculate that this result may rather be related to chemical properties of the odorants that have recently been found to interact with olfactory habituation (Sinding et al, ).…”

Attentional modulation of desensitization to odor

“…For curve fitting, we opted for a group-level method based upon classical analyses of human olfactory stimulus–response curves (Chastrette, Thomas-Danguin, & Rallet, 1998 ). An alternative, even preferable, method would have been to evaluate individual response curves prior to group-level tests (Sinding et al, 2017 ). However, this method was not selected due to the reduced signal-to-noise inherent in single prolonged exposures which is a limitation of the current study design.…”