Decomposition of an odorant in olfactory perception and neural representation

AbstractMolecules –– the elementary units of substances –– are commonly considered the units of processing in olfactory perception, giving rise to undifferentiated odor objects invariant to environmental variations. By selectively perturbing the processing of chemical substructures with adaptation, “the psychologist's microelectrode”, in a series of psychophysical and neuroimaging experiments (458 participants), we show that two perceptually distinct odorants sharing part of their structural features become significantly less discernible following adaptation to a third odorant containing their non-shared structural features, in manners independent of olfactory intensity, valence, quality, or general olfactory adaptation. The effect is accompanied by reorganizations of ensemble activity patterns in the posterior piriform cortex that parallel subjective odor quality changes, in addition to substructure-based neural adaptations in the anterior piriform cortex and amygdala. Thus, central representations of odor quality and the perceptual outcome embed submolecular structural information and are malleable by recent olfactory encounters. Usage NotesThe ‘preprocessed images.zip’ file contains fMRI data that has been preprocessed using the standard procedure in SPM12. EPI images have been corrected for slice timing differences and geometric distortion due to susceptibility artifacts, using participants’ field maps. They have been spatially realigned to the first volume of the first session (the initial baseline run on Day 1), unwarped to reduce movement-related variance, and smoothed by a Gaussian kernel with a 6-mm full width at half maximum to increase the signal-to-noise ratio.The ‘clean data.zip’ file contains fMRI data from which effects of no interest (motion regressors and low-frequency drift) have been subtracted. This was achieved using the AFNI programs 3dDeconvolve and 3dSynthesize.The ‘OdorDetectionTask.zip’ file contains the scripts for the task performed in the fMRI scanner.The ‘ROI.zip’ file contains the masks of the regions of interest used in the analysis.The ‘Results.zip’ file contains all the results.