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Updated: Mar 27, 2026
A Free-breathing fMRI Method to Study Human Olfactory Function
Published on: July 30, 2017
Temporal dynamics of olfactory training-induced neuroplasticity: an fMRI study using variable-onset hemodynamic
Hanani Abdul Manan1, Mei Ren2, Zetian Li2
1Smell and Taste Clinic, Department of Otorhinolaryngology, TU Dresden, Fetscherstrasse, 74, 01307 Dresden, Germany; Makmal Pemprosesan Imej Kefungsian (Functional Image Processing Laboratory), Department of Radiology, University Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Bandar Tun Razak, 56 000 Cheras, Kuala Lumpur, Malaysia.
Background:
Olfactory training (OT) is an established, behaviourally effective intervention for post-viral and idiopathic olfactory dysfunction, yet the temporal dynamics of its neural mechanisms remain insufficiently understood. Most neuroimaging studies rely on standard hemodynamic models that capture activation amplitude but overlook the timing and shape of the blood-oxygen-level-dependent (BOLD) response. Hence, we re-examined previous results on the effects of OT in patients with olfactory loss and healthy controls.
Methods:
Using a novel multi-model fMRI framework, we systematically mapped temporal tuning profiles of olfactory network responses in patients with olfactory dysfunction (PAT; n = 20) and matched healthy controls (CON; n = 19) before and after a 12-week OT program. For each subject, we generated a family of first-level models with systematically shifted hemodynamic onsets, allowing the estimation of region-specific response amplitude, latency, and waveform properties. Analyses focused on three key regions of interest (ROIs): the right insula, amygdala, and orbitofrontal cortex (OFC)-nodes critically implicated in olfactory perception and emotional-evaluative processing.
Results:
Before training, patients exhibited absent or weak BOLD responses across all ROIs. After training, they showed clear activation recovery ("gain-of-function"), characterized by delayed and broadened hemodynamic peaks relative to controls-indicative of slower but re-emerging network synchrony. In contrast, healthy controls displayed adaptive neural refinement, evidenced by amygdala habituation and a biphasic-like response in the OFC, reflecting efficient temporal reorganization of olfactory processing.
Conclusion:
Olfactory training induces state-dependent neural plasticity. In patients, recovery appears to involve broader and delayed engagement of olfactory networks, suggesting compensatory recruitment during sensory restoration. In contrast, healthy individuals show more precise and efficient neural responses after training. Together, these findings highlight different patterns of functional adaptation in the human olfactory system during recovery and learning.
