Pilot Study Using an NMDA Antagonist to Modulate Transcranial Direct Current Stimulation (tDCS) Effects on Sensory Discrimination

University of Ottawa

Status and phase: Unknown; Phase 2; Phase 1

Conditions: Schizophrenia

Treatments: Drug: Dextromethorphan; Device: Direct Current Stimulation

Study type: Interventional

Funder types: Other

Identifiers

NCT02426983

2013008

Details and patient eligibility

About

Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation which uses a very weak constant current to temporarily excite the brain area of interest via small electrodes placed on the scalp. Currently, tDCS is being used as a tool to investigate mental processes (cognition) and motor function (movement) in healthy controls and to treat neurological (i.e. stroke) and psychiatric (i.e. depression and dementia) patients. tDCS has been found to improve motor processes and cognitive performance, including attention and memory functions. This study will attempt to examine the effects of tDCS on a specific aspect of short term memory to sounds measured from electrical activity (EEG) from the top of the scalp. This study will also assess the effect of a drug, dextromethorphan (DMO), commonly found in cough syrup, which is thought to regulate tDCS treatment through brain receptors. The study involves four laboratory test sessions. EEG assessments will be done in two sessions involving 'anodal' tDCS stimulation (to temporarily excite cortical activity locally), one session with DMO treatment and one with placebo treatment, and two sessions involving 'sham' tDCS stimulation (device is turned off), with the same DMO and placebo treatments. These findings will contribute to our understanding of the brain chemistry involved in tDCS treatment and its effects on cognitive abilities.

Enrollment: 12 estimated patients

Sex: All

Ages: 18 to 35 years old

Volunteers: Accepts Healthy Volunteers

Inclusion criteria

• Healthy, medication free
• Non-smoker
• Right-handed

Exclusion criteria

• Any current or past Axis I or Axis II disorder including a current or recent history of alcohol/substance abuse
• A clinically significant medical illness or organic brain disorder known to cause psychosis or cognitive impairment
• Any neurological diagnosis (including epilepsy)
• Recent head trauma (<6 months)
• Metallic implants or any electrical device (e.g., pacemaker) in the body
• Major learning disability
• Body mass index >38kg/m¬2
• Use of illicit drugs
• Abnormal hearing

Trial design

12 participants in 4 patient groups, including a placebo group

Direct Current Stimulation active

Active Comparator group

Description:

Electrodes will be placed on the scalp overlying the left auditory cortex (anodal electrode) and on the contralateral forehead above the orbit (reference/cathode). Stimulation will be applied using a battery-driven constant-current regulator (Oasis Pro, Edmonton). In active tDCS sessions, the DC current will be initially increased in a ramp-like fashion over 10 s until reaching 2 mA and will be similarly decreased at the end of stimulation. In active tDCS, stimulation will be maintained for a total of 20 minutes. This will occur in two separate sessions, occurring within weeks.

Treatment:

Device: Direct Current Stimulation

Direct Current Stimulation sham

Sham Comparator group

Description:

In sham sessions, the device will have the same placement and intensity, but will only be turned on for 30 seconds. The DC current will be initially increased in a ramp-like fashion over 10 s until reaching 2 mA and will be similarly decreased at the end of stimulation. This will occur in two separate sessions, occurring within weeks.

Treatment:

Device: Direct Current Stimulation

NMDA antagonist active

Active Comparator group

Description:

Dextromethorphan (DMO), a non-competitive NMDA antagonist, will be delivered in the form of generic Life Brand Clear Cough Syrup DM (Trillium Healthcare Products Inc, Brockville, ON). Each subject will receive a dose of 50 ml DM with no-sugar cranberry juice (100 ml) to drink. This same dose will be delivered in two separate sessions, occurring within weeks.

Treatment:

Drug: Dextromethorphan

NMDA antagonist placebo

Placebo Comparator group

Description:

Each subject will receive a dose of a placebo (150 ml of no-sugar cranberry juice) to drink. This same dose will be delivered in two separate sessions, occurring within weeks.

Treatment:

Drug: Dextromethorphan