Glutamate, Learning, and Working Memory
- Registration Number
- NCT02769936
- Lead Sponsor
- University of California, Los Angeles
- Brief Summary
Impairments in plasticity and working memory in schizophrenia have been hypothesized to reflect dysfunction at the N-methyl-D-aspartate glutamate receptor (NMDAR). However, the specific mechanisms through which the NMDAR is involved in working memory versus plasticity differ. Towards gaining a deeper understanding of how NMDAR signaling relates to individual cognitive functions in healthy adults and patients with schizophrenia, the investigators used a single dose of d-cycloserine (DCS) as an experimental probe to examine the effects of enhancing NMDAR signaling on plasticity versus working memory in healthy adults and individuals with schizophrenia.
- Detailed Description
Background: Cognitive impairments in schizophrenia, such as deficits in plasticity and working memory, have been hypothesized to reflect dysfunction at the N-methyl-D-aspartate glutamate receptor (NMDAR). However, given that divergent properties of the NMDAR underlie its roles in plasticity versus working memory and that various aspects of NMDAR function are abnormal in schizophrenia, examining the effects of DCS in both healthy and patient populations is crucial.
Methods: The investigators used a single dose of the partial NMDAR agonist, d-cycloserine (DCS) to probe the effects of enhancing NMDAR signaling on working memory and plasticity. Working memory was assessed using a spatial n-back task. Plasticity was assessed using two learning tasks, the weather prediction task and information integration task, and an EEG paradigm that assesses changes in visual evoked potential amplitude following high frequency visual stimulation. Sixty-five healthy adults and forty-five schizophrenia patients were randomized to receive 100 mg acute DCS (healthy adult n = 32; schizophrenia n = 24) or placebo (healthy adult n = 33; schizophrenia n = 21).
Recruitment & Eligibility
- Status
- COMPLETED
- Sex
- All
- Target Recruitment
- 110
Not provided
Not provided
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- PARALLEL
- Arm && Interventions
Group Intervention Description Healthy Adult - Placebo Placebo Single dose placebo pill in healthy adults Schizophrenia - Placebo Placebo Single dose placebo pill in schizophrenia patients Healthy Adult - D-cycloserine D-cycloserine Single 100 mg dose D-cycloserine pill in healthy adults Schizophrenia - D-cycloserine D-cycloserine Single 100 mg dose D-cycloserine pill in schizophrenia patients
- Primary Outcome Measures
Name Time Method Performance on Information Integration Learning Task Testing Day (i.e. approx 3-5 hrs following placebo or D-cycloserine administration) Percent Correct Responses out of 240 trials (for schizophrenia patients) or 320 trials (for healthy adults) on the Information Integration Learning Task, which is a classification learning task in which participants learn to classify visual stimuli as category A or B following practice with stimuli and auditory feedback indicating correct versus incorrect responses.
Performance on Weather Prediction Learning Task Testing Day (i.e. approx 3-5 hrs following placebo or D-cycloserine administration) Percent Correct Responses out of 240 trials (for schizophrenia patients) or 320 trials (for healthy adults) on the Weather Prediction Learning Task, which is a probabilistic classification learning task in which participants learn to predict the weather (i.e. "sun" or "rain" outcomes) based on combinations of cues that predict "sun" versus "rain" outcomes.
Performance on N-Back Working Memory Task Testing Day (i.e. approx 3-5 hrs following placebo or D-cycloserine administration) Percent Correct Responses out of 240 trials (for schizophrenia patients) or 320 trials (for healthy adults) on the N-Back Task, which is a spatial working memory task in which participants identify whether each new stimulus on the computer screen is in the same location as the stimulus shown in trials ago. Patients with schizophrenia completed 80 trials at each of 3 working memory loads (0-, 1-, 2-back loads) and healthy adults completed 80 trials at each of 4 working memory loads (0-, 1-, 2-, 3-back loads).
Change in Visual Evoked Potential Amplitude using Electroencephalograph (EEG) Testing Day (i.e. approx 3-5 hrs following placebo or D-cycloserine administration) EEG data were recorded using a 128 channel cap while participants viewed a black and white checkerboard stimulus on a computer screen in 6 x 2-minute blocks before and after viewing a quickly flashing checkerboard stimulus for 2 minutes. Change in the mean amplitude of the visual evoked potential from before versus after viewing the quickly flashing checkerboard stimulus was used to assess plasticity.
- Secondary Outcome Measures
Name Time Method