The goal of this clinical trial is to learn whether certain methods of detecting awareness in vegetative or minimally conscious patients (using neuroimaging) are sensitive to the effects of psilocybin (a psychedelic drug). One of these methods includes scanning peoples' brains while they watch a film. When different individuals watch a film, their brains become synchronized with each other as they watch the plot unfold. Most importantly, if a seemingly unconscious patient also shows the same brain-synchronization, it means they might actually be conscious and aware.

To approach this goal, the investigators will be carrying out this trial in healthy volunteers. This will help better understand whether psilocybin may be a potential treatment for restoring awareness in these patients. The main questions it aims to answer are:

• Does psilocybin enhance or diminish brain synchrony during a film?
• Do changes in brain synchrony reflect differences in each individual's conscious experience?

Participants will be asked to:

• Attend two brain scanning sessions and watch a series of film clips, perform a brief mental imagery task, and listen to music - once under a placebo, and once under psilocybin.
• Play a series of games that assess their cognition (memory, reasoning, planning, etc.).
• Perform a series of visual illusions tasks.

Inclusion Criteria:

Participants must:

• Have access to an internet connection
• Be in good general health
• Be 19 years of age, or older
• Be willing to follow the study protocol

Exclusion Criteria:

The following people will be excluded from the study. Those who:

• Are unable to read English
• Have high blood pressure
• Are pregnant (determined by a urine pregnancy test at in-person screening)
• Are not using effective methods of contraception with their partner(s) (e.g. oral contraceptive pill, injection, implant, patch, vaginal ring, intrauterine coil, intrauterine device, tubal ligation, or barrier method)
• Are taking chronic administration of tricyclic antidepressants and/or lithium
• Are taking acute administration of serotonin reuptake inhibitors
• Are currently using the antipsychotic medication haloperidol
• Are currently using monoamine oxidase inhibitors
• Have any current or past history of meeting the Diagnostic and Statistical Manual of Mental Illnesses (DSM-V) criteria for schizophrenia, bipolar I, bipolar II, or psychotic symptoms
• Have any first or second-degree relatives with history of above disorders/symptoms
• Have any other diagnosed and/or extreme psychiatric disorders, such as anxiety, depression, post-traumatic stress disorder (PTSD), addiction, obsessive-compulsive disorder (OCD), etc.
• Have any history of suicidal behaviour or current/recent suicidal ideation (determined by the Columbia-Suicide Severity Rating Scale [C-SSRS] at in-person screening)