Future directions
visual hallucinations, psychosis
CORTEX
Our results suggest that local gain is changed under LSD implicating disturbances of the E/I balance as a neural mechanism underlying LSD effects. Because rDCM summarises region-specific E/I balance by a single parameter per region, we cannot determine whether excitation, inhibition, or both are impacted. Future studies should employ more detailed models that allow to pinpoint these changes and compare them empirically to other conditions in which the E/I balance is affected, for example psychosis [Furthermore, our results suggest that visual regions may be impacted quite differently both in terms of between-region connectivity as well as in terms of local gain compared to the rest of the cortex warranting further investigation. The physiological basis of these changes and the relationship with subjective effects—visual hallucinations in particular—should be examined in future studies. A comparison of eyes-open vs eyes-closed resting states would be valuable to determine whether the EC changes observed here are a reflection of eyes-open-like behaviour of the visual system.Finally, we found that both whole-brain FC and EC were equally capable of discriminating between LSD and placebo with high accuracy suggesting that both are promising candidates for more challenging prediction targets. More research is needed to assess whether machine learning models trained on either FC and EC estimates are able to predict subjective effects of LSD at an individual level or from baseline EC measured before LSD intake.