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

Summary

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.

Conditions

• Schizophrenia

Interventions

DEVICE

Direct Current Stimulation

Comparison between active Direct Current Stimulation (2 mA, 20 minutes) and Sham stimulation (the device is set up, but only turned on for 30 seconds). Conductive saline-soaked rubber electrodes super-imposed on sponge plates 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. For 'sham' stimulation, the device will only be turned on for 30 seconds. This will occur in two separate sessions, occurring within weeks.

DRUG

Dextromethorphan

Comparison between Dextromethorphan and a no-sugar placebo. 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), which has high dose of DMO (15 mg/5 ml) with no other major additives. Each subject will receive a dose of 50 ml DM with no-sugar cranberry juice (100 ml) to drink from a mug, while wearing a nose plug. This same dose will be delivered in two separate sessions, occurring within weeks. Each subject will receive a dose of a placebo (150 ml of no-sugar cranberry juice) to drink from a mug, while wearing a nose plug. This same dose will be delivered in two separate sessions, occurring within weeks.

Sponsors & Collaborators

• University of Ottawa

  lead OTHER

Principal Investigators

• Danielle Impey, Ph.D. (cand.) · University of Ottawa

Study Design

Allocation

RANDOMIZED

Masking

DOUBLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

35 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2015-04-30

Primary Completion

2015-09-30

Completion

2016-04-30

Countries

• Canada

Study Locations