LSD administration significantly increased thalamic functional connectivity to various cortical regions.
Alterations were observed across all dimensions of the following LSD administration.
Increased thalamic connectivity was specifically noted with regions associated with auditory and visual hallucinations.
Significant correlations were found between thalamic connectivity to the right fusiform gyrus and insula and subjective visual and auditory effects of the drug.
These findings may suggest that hallucinogenic drug effects are linked to enhanced cortical excitability through interactions within the thalamocortical system.
Simplified
OBJECTIVE: It has been proposed that the thalamocortical system is an important site of action of hallucinogenic drugs and an essential component of the neural correlates of consciousness. Hallucinogenic drugs such as LSD can be used to induce profoundly altered states of consciousness, and it is thus of interest to test the effects of these drugs on this system.
METHOD: 100 μg LSD was administrated orally to 20 healthy participants prior to fMRI assessment. Whole brain thalamic functional connectivity was measured using ROI-to-ROI and ROI-to-voxel approaches. Correlation analyses were used to explore relationships between thalamic connectivity to regions involved in auditory and visual hallucinations and subjective ratings on auditory and visual drug effects.
RESULTS: LSD caused significant alterations in all dimensions of the and significantly increased thalamic functional connectivity to various cortical regions. Furthermore, LSD-induced functional connectivity measures between the thalamus and the right fusiform gyrus and insula correlated significantly with subjective auditory and visual drug effects.
CONCLUSION: Hallucinogenic drug effects might be provoked by facilitations of cortical excitability via thalamocortical interactions. Our findings have implications for the understanding of the mechanism of action of hallucinogenic drugs and provide further insight into the role of the 5-HT-receptor in altered states of consciousness. 2A
Key numbers
104 of 130
Increased Thalamic Connectivity
Significant connectivity increase between thalamus and brain regions under LSD vs. placebo.
1.3 ± 0.6 ng/ml
Plasma LSD Level at 2h
Mean plasma concentration of LSD measured 2 hours after administration.
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