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| Poster #246 Odor Specific Activation Patterns in the Human Olfactory Bulb Detected by High Resolution BOLD fMRI on 7 Tesla |
| Xinyi Zhou1,2,3, Adrian G. Paez1,2, Gaoqiang Xu1,2, Yu Luo1,2, Xinyuan Miao4, Peter C.M. Van Zijl1,2, Arnold Bakker5,6, Vidyulata Kamath6, Jun Hua1,2 1Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States 2F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, 3Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, 4Department of Radiology, Johns Hopkins Hospital, Baltimore, MD, 5Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, 6Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, |
Most knowledge of the human olfactory system is based on rodent studies,despite interspecies differences.In rodents, a tight correspondence exists between olfactory bulb (OB) glomeruli and sensory neurons,but this organization may differ in humans,who have more glomeruli and sensory neuron types.Human OB activation patterns during olfactory stimulation remain largely unexplored due to limited neuroimaging techniques.Recently, our group demonstrated that T2-prepared BOLD fMRI at 7T reliably measures functional activation in the human OB.This study evaluates whether this method detects odor-specific activation patterns.Five healthy volunteers(25.3±3.3yr; UPSIT 37±2) underwent 7T MRI with two odorants: phenylethyl alcohol(Odor 1) and ethyl hexanoate(Odor 2). Odorless mineral oil served as a control. A custom olfactometer delivered stimuli. 6 ROIs, including the OB, piriform cortex, and other secondary olfactory cortex, were analyzed with 0.5 mm 3D T1w, 0.4 mm 3D T2w, and 1.5 mm T2prep BOLD fMRI. Functional activation was assessed using the Kolmogorov–Smirnov test, and relative signal changes (ΔS/S) were calculated. Robust activation was detected in all ROIs. The OB showed greater ΔS/S than other ROIs, though its time courses were noisier. Odor 1 produced fewer activated voxels and lower ΔS/S than Odor 2. OB activation patterns differed, clustering anteriorly for Odor 1 and posteriorly for Odor 2. Habituation effects were insignificant. This pilot study shows that T2prep BOLD fMRI can detect odor-specific patterns in the human OB, overcoming challenges of small size and susceptibility artifacts. Human OB variability, with blended layers and subject-specific differences, complicates findings. Further validation is needed, but this approach holds promise for mapping individual OB activation patterns. |