FMRI activation to cannabis odor cues is altered in individuals at risk for a cannabis use disorder.

INTRODUCTION: The smell of cannabis is a cue with universal relevance to cannabis users. However, most cue reactivity imaging studies have solely utilized visual images, auditory imagery scripts, or tactile cues in their experiments. This study introduces a multimodal cue reactivity paradigm that includes picture, odor, and bimodal picture + odor cues. METHODS: Twenty-eight adults at risk for cannabis use disorder (CUD; defined as at least weekly use and Substance Involvement Score of ≥4 on the Cannabis sub-test of the Alcohol, Smoking and Substance Involvement Screening Test) and 26 cannabis-naive controls were exposed to cannabis and floral cues during event-related fMRI. Between-group differences in fMRI activation and correlations were tested using FMRIB's Local Analyses of Mixed Effects and corrected for multiple comparisons using a voxelwise threshold of z > 2.3 and a corrected cluster threshold of p < .05. RESULTS: Both visual and olfactory modalities resulted in significant activation of craving and reward systems, with cannabis odor cues eliciting a significantly greater response in regions mediating anticipation and reward (nucleus accumbens, pallidum, putamen, and anterior insular cortex, supplementary motor area, angular gyrus and superior frontal gyrus) and cannabis picture cues eliciting a significantly greater response in the occipital cortex and amygdala. Furthermore, the CUD group showed significantly increased activation in the ventral tegmental area (VTA), the insula, and the pallidum compared to controls. Within the CUD group, activation in the insula, anterior cingulate, and occipital cortex to bimodal cannabis cues was significantly correlated with self-reported craving. CONCLUSION: Our multimodal cue reactivity paradigm is sensitive to neural adaptations associated with problematic cannabis use.

FMRI correlates of olfactory processing in typically-developing school-aged children.

Human olfactory processing is understudied relative to other sensory modalities, despite its links to neurodevelopmental and neurodegenerative disorders. To address this limitation, we developed a fast, robust fMRI odor paradigm that is appropriate for all ages and levels of cognitive functioning. To test this approach, thirty-four typically developing children aged 7-12 underwent fMRI during brief, repeated exposure to phenylethyl alcohol, a flower-scented odor. Prior to fMRI scanning, olfactory testing (odor detection and identification) was conducted. During fMRI stimulus presentation, odorant release was synchronized to each participant's inspiratory phase to ensure participants were inhaling during the odorant exposure. Between group differences and correlations between activation and odor detection threshold scores were tested using the FMRIB Software Library. Results demonstrated that our 2-min paradigm significantly activated primary and secondary olfactory regions. In addition, a significant relationship between odor detection threshold and higher activation in the right amygdala and lower activation in the left frontal, insular, occipital, and cerebellar regions was observed, suggesting that this approach is sensitive to individual differences in olfactory processing. These findings demonstrate the feasibility of studying olfactory function in children using brain imaging techniques.