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.

Characterizing Olfactory Function in Children with Autism Spectrum Disorder and Children with Sensory Processing Dysfunction.

Abnormalities in olfactory function have been identified in a number of neurological and psychiatric disorders, including Parkinson's disease and schizophrenia. However, little is known about olfactory function in autism spectrum disorder (ASD). The present study aims to assess the olfactory profiles of children with ASD, compared to an age- and sex-matched comparison group of typically developing children and a second clinical control group consisting of non-ASD children with sensory processing dysfunction (SPD). Participants completed a battery of sensory and behavioral assessments including olfactory tasks (Sniffin' Sticks Threshold Test and self-reported valence ratings for two target odorants (phenylethyl alcohol and vanillin) and the University of Pennsylvania Smell Identification Test), and an autism evaluation (Autism Diagnostic Observation Schedule-2). Children with ASD showed intact odor detection with reduced odor identification ability. Poor odor identification was significantly correlated with autism symptom severity. Children with SPD demonstrated reduced odor detection and identification ability. These findings provide evidence for differential patterns of smell processing among ASD and non-ASD neurodevelopmental disorders. Future studies are needed to determine whether the association of impaired olfaction and increased autism symptoms is due to shared etiology.

A multimodal investigation of cerebellar integrity associated with high-risk cannabis use.

With legalization efforts across the United States, cannabis use is becoming increasingly mainstream. Various studies have documented the effects of acute and chronic cannabis use on brain structure and cognitive performance, including within the frontal executive control network, but little attention has been given to the effects on the cerebellum. Recent evidence increasingly points to the role of the cerebellum in various nonmotor networks, and the cerebellum's expression of cannabinoid receptors may pose particular vulnerabilities to the consequences of cannabis use. Using a combined approach of resting-state functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI), the present study aims to assess how cannabis use relates to the cerebellum's intrinsic functional connectivity and underlying white matter structure and whether these properties are associated with craving or severity of cannabis use. Resting-state fMRI and DTI data, as well as self-reports of substance use history, were analyzed from a sample of 26 adults at risk for cannabis use disorder (CUD) and an age- and sex-matched comparison group of 25 cannabis-naïve adults (control). Results demonstrated that individuals at risk for a CUD showed key differences in cerebellar functional connectivity, with specific impacts on the dorsal attention and default mode networks. In addition, group differences in white matter were localized to the middle cerebellar peduncle (MCP), with a relationship between lower MCP diffusivity and higher levels of self-reported craving. These findings lend further support to the cerebellum's role in key cognitive networks and potential consequences for substance use disorders.

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.