Fig. 2

'PSILAUT' recruitment and study procedures. Autistic and non-autistic participants will be recruited from existing local research databases, advertising on the King’s College London website and wider dissemination of study information. Participants are welcome to self-refer. Autistic participants will also be recruited from clinical contacts from South London and Maudsley NHS trust, local and national support groups and via the Cambridge Autism Research Database (CARD), managed by our collaborators at the Autism Research Centre, University of Cambridge. Interested participants will be sent an information sheet and screened via video call or phone for eligibility according to the inclusion and exclusion criteria prior to the first visit. Written consent will be sought after inclusion criteria are confirmed and the participant is then assigned to a study schedule. Participants will be provided with login details to an online platform (Delosis Ltd., London) to complete a battery of questionnaires remotely. Participants will visit the study site on three separate occasions. A blood sample will be collected on one of the three visits for quantification of whole blood serotonin levels. Each participant will complete an MRI scan session to acquire a structural, resting-state functional MRI scan and a face emotion processing task. The EEG paradigm will include resting-state and functional activation during a face processing, auditory oddball and visual processing. Psychophysical tasks will be collected prior to a cognitive battery which will include the ‘reading the mind in the eyes’ (RMET), probabilistic reversal learning (PRT), both of which will be delivered using PsyTools (Delosis Ltd., London) and a semantic verbal fluency task. The 5-dimensional altered states of consciousness (5D-ASC) questionnaire will then be completed to quantify any subjective effects experienced by participants