6:05pm - 7:05pm
Effects of Psilocybin-Assisted Psychotherapy on the Emotional and Reward Processing of Music
Music serves as an emotionally evocative and rewarding stimulus, with musical surprises, or prediction errors, playing a key role in the hedonic quality of music. This project sought to use subjective, behavioural and fMRI measures of music-evoked pleasure and emotion to assess the mechanistic differences through which psilocybin may mediate its therapeutic effects compared to the selective serotonin reuptake inhibitor, escitalopram. 41 participants with Major Depressive Disorder were randomised to either psilocybin (n=22) or escitalopram (n=19) treatment group. Participants were enrolled in magnetic resonance imaging (fMRI) while listening to a 7-minute music piece under eyes-closed conditions both before and after a 6 week treatment period. Additionally, participants listened to the piece again while continuously tracking their emotional experience, and surprise-related affective indices were used to determine the effect of music surprises on valence and arousal. Time courses for musical surprises were entered into subject-level fMRI analyses as regressors of interest and treatment effects were assessed on a group level subsequently. Psychophysiological interactions (PPIs) were carried out to further investigate underlying treatment differences in surprise-related changes in functional connectivity. Results showed that SSRI treatment caused a decrease in surprise-related affective response post-treatment, while no difference was reported following psilocybin. A significant surprise-related decrease in activation of the ventromedial prefrontal cortex was reported following psilocybin therapy. Increased functional coupling of the superior temporal gyrus and paracingulate cortex was seen in response to musical surprises in escitalopram. These findings shed light on how psilocybin varies from SSRI treatment in its effect on the neural and affective processing of rewarding musical stimuli and offers insight into their divergent therapeutic mechanisms.