None listed
Conditions
Brief summary
Our previous research demonstrated similarities between dexamphetamine effects in healthy volunteers in illusions involving visual and tactile stimuli and the experience of the same illusions in people with schizophrenia experiencing passivity symptoms. Passivity symptoms are the feeling of being controlled by an external force and not being the agent of one's own actions, thoughts or feelings, one of the first rank symptoms that also includes hearing voices talking "in one's head", the belief that thoughts are being inserted into or withdrawn from one’s conscious mind, or the belief that one’s thoughts are being broadcast to other people). To further elucidate the role of dopamine in these phenomena, we will determine if the effects of dexamphetamine are based on specific actions on the visual sensory system, the tactile sensory system, or the higher level integration of both. In addition, we will determine if the effects are specific to the integration of these two sensory systems, or if they generalise to other sensory systems, especially the auditory system, which prior research indicates is more affected than the visual system by both dexamphetamine and in schizophrenia. Prior research from our lab indicates that that there is a dopamine-dependent widening of the window of the time in which stimuli become associated, either in a way to bind them as a single perceptual experience, or in a way that is perceived as a causal relationship, that may provide a common mechanism to explain many of the symptoms and signs of schizophrenia, especially the first-rank symptoms including passivity symptoms. The broad purpose of this study is the elucidation of the role of the dopamine in abnormal perceptual experiences, by manipulating dopamine levels with dexamphetamine and measuring the consequence on the experience of illusions, especially under conditions in which we assess the temporal window of associability, as compared with other similar research in people with schizophrenia.
Interventions
dexamphetamine (0.45 mg/kg, by mouth with gelatine capsules) once only, and placebo: gelatine capsules filled with glucose. The two treatments are given about a week apart (minimum 5 days). Dexamphetamine levels determined from five saliva samples taken throughout the day, at about 70 min intervals.
Sponsors
Mathew Martin-Iverson
Study design
Allocation
Non-randomised trial
Intervention model
Crossover
Primary purpose
Treatment
Masking
Blinded (masking used) (Subject, Caregiver, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to 59 Years
Healthy volunteers
Yes
Inclusion criteria
Healthy people >17 and <60 years of age
Exclusion criteria
1. Heart or severe blood vessel disease, 2. High blood pressure (> 180/90 mm Hg), 3. Glaucoma, 4. Hyperthyroidism (overactive thyroid), 5. Tics (muscle twitching usually in the face or shoulders), 6. Sensitivity to dexamphetamine or sympathomimetic amines, 7. Any degenerative disease of the nervous system, 8. Epilepsy, or other neurological disorder, including head injury. 9. Tourette's syndrome or a family history of this disorder, 10. A psychiatric or psychological problem for which they are receiving treatment (schizophrenia, depression, anxiety, etc), 11. A serious medical problem for which they are receiving treatment (cardiovascular disorders, respiratory disorders, etc), 12. Had or are currently receiving treatment for substance abuse, 13. A family history of schizophrenia in first-degree relatives (parents, children or siblings), 14. Previously experienced hypersensitivity to dexamphet-amine, 15. Used any drug including alcohol or any illicit drug within 24 hours of each testing session, 16. Used caffeine on the day of each testing session, 17. Current prescription medication that you are taking other than contraceptives or acne medication 18. Used over-the-counter medication in the 48 hours before each testing session
Outcome results
None listed