Clinical TrialHealthy VolunteersPsilocybinPlaceboPsilocybinPlaceboTerminated

Visual Surround Suppression and Perceptual Expectation Under Psilocybin

The prospective study will address the critical need for more precise characterizations of the acute visual effects of the drug psilocybin by measuring the impact of acute psilocybin intoxication on a perceptual task known as visual surround suppression, compared to an active placebo control.

Target Enrollment
10 participants
Study Type
Phase I interventional
Design
Randomized, triple Blind

Detailed Description

This basic-science, randomized, triple-masked crossover study in healthy volunteers examines acute effects of psilocybin (25 mg) versus active placebo (niacin 100 mg) on visual surround suppression and perceptual expectation.

Data will inform how psilocybin impacts contextual processing and serotonergic contributions to surround suppression, complementing findings in clinical populations and advancing knowledge of human visual neurobiology.

Study Protocol

Preparation

sessions

Dosing

2 sessions

Integration

sessions

Study Arms & Interventions

Psilocybin first

experimental

Crossover: participants receive psilocybin in first session and niacin in second (washout between sessions).

Interventions

  • Psilocybin25 mg
    via Oral• single dose• 1 doses total

    25 mg capsule (Capsugel Vcaps Plus HPMC size 2).

  • Placebo100 mg
    via Oral• single dose• 1 doses total

    Niacin 100 mg (active placebo; Vitamin B3).

Niacin first

experimental

Crossover: participants receive niacin in first session and psilocybin in second (washout between sessions).

Interventions

  • Psilocybin25 mg
    via Oral• single dose• 1 doses total

    25 mg capsule (Capsugel Vcaps Plus HPMC size 2).

  • Placebo100 mg
    via Oral• single dose• 1 doses total

    Niacin 100 mg (active placebo; Vitamin B3).

Participants

Ages
25 – 65
Sexes
Male & Female

Inclusion Criteria

  • Inclusion Criteria:
  • Have given written informed consent
  • Have at least a high-school level of education or equivalent (e.g. GED), and be able to read and write in English
  • General health status: Participants should be in good physical (BMI between 20.0 and 28.0 kg/m2) and psychiatric health.
  • Experience taking psilocybin (at the PI's discretion).
  • Participants must also have a person that can reliably transport them to and from the CRU for dosing session days.
  • Geographic location: Minnesota counties that are approximately within 1 hour driving distance to Twin Cities, including not limited to Hennepin, Ramsey, Washington, Anoka, Wright, Carver, Scott, Dakota, Sherburn
  • Participants must be willing to wear a face mask at all times during in-person study visits, except for dosing sessions, to ensure COVID-19 protection.
  • Participants must be willing to get a COVID-19 test and share results with the study team prior to all in-person visits.
  • Participants must be up-to-date on COVID-19 vaccines, per CDC guidelines, and share a copy of their proof of vaccination status with the study team prior to the consenting visit.
  • Agrees to refrain from using recreational drugs while enrolled in the study, including, but not limited to, hallucinogens, ketamine, and marijuana.

Exclusion Criteria

  • Exclusion Criteria:
  • Current or past history of meeting DSM-5 criteria for schizophrenia spectrum or other psychotic disorders (except due to another medical condition), or Bipolar I or II Disorder, personality disorder, major depressive disorder, posttraumatic stress disorder, panic disorder, obsessive compulsive disorder, dysthymic disorder.
  • Current or past history within the last 5 years of meeting DSM-5 criteria for a moderate or severe alcohol or drug use disorder (excluding caffeine, nicotine, and hallucinogens)
  • Those with a first or second-degree relative with a current or past history of meeting DSM-5 criteria for schizophrenia or other psychotic disorders or bipolar I or II disorder, because they might have an underlying genetic susceptibility for psychosis.
  • Presence of symptoms of the following DSM-5 disorders within the past 6 months (as assessed by the MINI-7):
  • * Major depressive Episode
  • * Suicidality
  • * Manic and Hypomanic Episodes
  • * Panic disorder
  • * Agoraphobia
  • * Social Anxiety Disorder
  • * Obsessive-Compulsive Disorder
  • * Posttraumatic Stress Disorder
  • * Alcohol Use Disorder
  • * Substance Use Disorder (Non-Alcoholic)
  • * Psychotic Disorders and Mood Disorders with Psychotic Features
  • * Anorexia Nervosa
  • * Bulimia Nervosa
  • * Binge Eating Disorder
  • * Generalized Anxiety Disorder
  • * Antisocial Personality Disorder
  • * Mood Disorders:
  • * Major Depressive Disorder (MDD)
  • * MDD with Psychotic Features
  • * Bipolar I
  • * Bipolar II
  • * Other Specified Bipolar and Related Disorder
  • Presence of abuse or dependence of drugs measured by the MINI-7 in the past 12 months (listed categories e.g., stimulants, cocaine, opiates, dissociatives, inhalants, cannabis, sedatives, miscellaneous).
  • History of medication or substance induced psychosis.
  • Medically significant condition considered unsuitable for the current study (e.g. diabetes, epilepsy, severe cardiovascular disease, etc)
  • History of suicide attempts or mania
  • Positive pregnancy test or currently breast-feeding
  • Currently taking on a regular (e.g., daily) basis any prescription medications, with the exception of birth control or other hormone therapy
  • A strong bias either for or against psychedelic substances, or if their responses about psychedelic use indicate that they abuse them from frequent use (more than once per month, with the exception of microdosing).
  • MRI EXCLUSION: head trauma, claustrophobia incompatible with scanning, cardiac pacemaker, implanted cardiac defibrillator, aneurysm brain clip, inner ear implant, prior history as a metal worker and/or certain metallic objects in the body that cannot be approved for MR scanning by the CMRR safety committee, history of clinically significant vertigo, seizure disorder, middle ear disorder, or double vision, or tattoos done less than 4 weeks from the first scheduled MRI.
  • Significant movement disorders including tardive dyskinesia that could disrupt EEG recordings will also be excluded.
  • Uncontrolled hypertension, with an average blood pressure reading across 4 measurements over 2 separate days greater than 140/90mmHg.
  • Unwilling to wear a face mask during in-person study visits that require them.
  • Unwilling to get tested for COVID-19 and share results with study personnel prior to all in-person visits.
  • Are unvaccinated against COVID-19, are not current with their COVID-19 vaccine booster, or are unwilling to share their proof of COVID-19 vaccination with the study team.

Study Details

Locations

University of Minnesota — Minneapolis, Minnesota, United States

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