Poster No:
2477
Submission Type:
Abstract Submission
Authors:
Rui Dai1, Zirui Huang1, George Mashour1
Institutions:
1University of Michigan, Ann Arbor, MI
First Author:
Rui Dai
University of Michigan
Ann Arbor, MI
Co-Author(s):
Introduction:
The neurobiology of the psychedelic experience is not fully understood. Identifying common neural changes induced by both classical (i.e., acting at the 5-HT2 receptor) and non-classical psychedelics would provide mechanistic insight into state-specific characteristics. Previous studies of psychedelic effects on the brain focused primarily on connectivity between different brain regions and networks. However, less is known about how psychedelics affect neural activity coordinated within local brain regions. To address this gap, we investigated the impact of nitrous oxide, ketamine and lysergic acid diethylamide (LSD) on regional homogeneity in human cortex.
Methods:
This study was a reanalysis of three neuroimaging datasets from healthy human volunteers, who were assessed by fMRI during baseline (i.e., ordinary awake state) and during exposure to psychedelic concentrations of nitrous oxide (n=16), ketamine (n=12), and LSD (n=15). Regional homogeneity (ReHo) analysis was employed to assess the similarity or coherence of spontaneous neural activity within a specific region of the brain. The impact of different regional homogeneity cluster sizes (7 – 729 voxels) was also examined. Additionally, a support vector machine learning approach was utilized to classify baseline and psychedelic states based on the regional homogeneity features derived from distinct brain functional networks.
Results:
Despite distinct molecular mechanisms and modes of delivery, all three psychedelics consistently reduced regional homogeneity in functional networks, including visual (nitrous oxide vs. baseline: p=0.033, ketamine vs. baseline: p=0.038, LSD vs. baseline: p=0.0002), dorsal attention (nitrous oxide vs. baseline: p=0.005, ketamine vs. baseline: p=0.010, LSD vs. baseline: p=0.0006), frontoparietal (nitrous oxide vs. baseline: p=0.0007, ketamine vs. baseline: p= 0.001, LSD vs. baseline: p<0.0001), and default mode (nitrous oxide vs. baseline: p=0.021, ketamine vs. baseline: p= 0.014, LSD vs. baseline: p=0.0005) networks. All p values were Bonferroni corrected. Furthermore, compared to baseline, psychedelic-induced changes in regional homogeneity was more consistent with small ReHo cluster size (e.g., 7-27 voxels). As the ReHo cluster size increased (e.g., 125-729 voxels), the difference between psychedelic states and baseline diminished. Lastly, the results from the support vector machine demonstrated the following prediction accuracies for distinguishing between baseline and psychedelic states: 75% for nitrous oxide, 67% for ketamine, and 83% for LSD.
Conclusions:
We conclude that classical and non-classical psychedelics share a common effect of reducing local coherence of neural activity in areas of known relevance to consciousness, suggesting a common candidate mechanism for the psychedelic experience.
Modeling and Analysis Methods:
Task-Independent and Resting-State Analysis 2
Perception, Attention and Motor Behavior:
Consciousness and Awareness 1
Keywords:
Consciousness
Other - Nitrous Oxide; Ketamine; LSD; fMRI;Regional homogeneity
1|2Indicates the priority used for review
Provide references using author date format
Carhart-Harris. (2016), 'Neural correlates of the LSD experience revealed by multimodal neuroimaging', Proceedings of the National Academy of Sciences, vol. 113, no. 17, pp. 4853-4858.
Dai, Rui. (2023), 'Classical and non-classical psychedelic drugs induce common network changes in human cortex', NeuroImage, vol. 273, no.120097.
Zang YF. (2004), 'Regional homogeneity approach to fMRI data analysis', NeuroImage, vol. 22, no. 1, pp. 394-400.