N-methyl-D-aspartic Acid (NMDA) and Cognitive Remediation in Schizophrenia

Summary

Persistent neurocognitive deficits are a major cause of severe disability and impaired long-term psychosocial outcome in schizophrenia (SZ). In particular, within the auditory system, early deficits such as the behavioral and neurophysiological ability to match tones that vary in pitch correlate with impairments in auditory emotion recognition (affective prosody) and general functioning, suggesting that interventions aimed at remediating sensory-level dysfunction may lead to significant improvement in higher order cognitive/emotion processes. Efforts to ameliorate cognitive deficits in schizophrenia utilize either pharmacological agents or behavioral treatments such as cognitive remediation, which generally focus on higher order processes, and not on the early sensory processing which may be key to functioning.

Numerous pharmacological agents have been proposed, but accumulating evidence suggests that dysfunction of the N-methyl-D-aspartic acid (NMDA) receptor may be one of the root causes of schizophrenia, including sensory and cognitive impairments, suggesting that an NMDA based treatment may be efficacious in reversing these deficits. D-Cycloserine, a synthetic partial NMDA agonist has been used in anxiety disorders to augment learning in cognitive remediation. Because of a tendency to act as an NMDA antagonist at higher doses D-cycloserine is not effective in schizophrenia. In contrast, D-serine (DSR), is a full agonist, and is therefore more ideal for enhancing NMDA function and cognitive remediation. While previous use of DSR was limited by safety concerns in rodents,the investigators have shown that it can safely be used at doses of 60 mg/kg and, moreover, demonstrates converging improvement in symptomatic, cognitive and sensory-based measures in schizophrenia. Evidence also suggests that NMDA receptor dysfunction in schizophrenia may be relative, rather than absolute, suggesting that the enhanced practice of a cognitive remediation paradigm might be able to overcome reduced plasticity and treat cognitive dysfunction.

This project will be the first to combine the NMDA based and sensory-based cognitive remediation (SBR) approaches, and will utilize not only DSR, but also a tone matching SBR paradigm has been shown to enhance learning in healthy controls, as well as a paradigm designed to augment visual motion detection. This study will pilot these interventions in a double-blind, placebo-controlled, randomized crossover design that will use neurophysiology together with cognitive tests to explore the effects on brain activity and cognitive function in 16 patients with schizophrenia or schizoaffective disorder. The investigators hypothesize that DSR+SBR will lead to improvement. Subjects will have an initial visit to establish baseline performance on cognitive tasks before returning for 3 visits when they will receive blinded study medication \[60 mg/kg of DSR (2 days) or placebo (1 day)\] in a randomized order. The procedures on the treatment days will include the SBR paradigm and pre/post neurophysiological measurements. Primary outcomes are improvements in neurophysiologic and behavioral sensory processing. The main goal is to establish the preliminary efficacy to use in a follow-up multi-dose study utilizing a multiple session SBR R01 application.

Conditions

• Schizophrenia
• Schizoaffective Disorder

Interventions

DRUG

D-serine

Subjects will then undergo three treatment visits. Each visit will begin with a pre treatment MMN/visual motion paradigm. Subjects will then receive DSR (60 mg/kg) or placebo and begin a one-hour SBR intervention. SBR will begin approximately 30 minutes after drug administration, to coincide with peak serum DSR level. Finally, to evaluate the effects of SBR and NMDA treatment on neurophysiology, subjects will complete a post treatment ERP paradigm. Treatment days will be separated by 1 week to reduce carryover effect. To increase power, each subject will undergo two DSR treatment days and 1 placebo day, with the placebo day selected randomly from among the three treatment days, in counter balanced order. Treatment assignment (drug and SBR) will be double blinded. Follow-up cognitive and safety measures will also be completed on the final treatment day.

DRUG

placebo

Subjects will then undergo three treatment visits. Each visit will begin with a pre treatment MMN/visual motion paradigm. Subjects will then receive DSR (60 mg/kg) or placebo and begin a one-hour SBR intervention. SBR will begin approximately 30 minutes after drug administration, to coincide with peak serum DSR level. Finally, to evaluate the effects of SBR and NMDA treatment on neurophysiology, subjects will complete a post treatment ERP paradigm. Treatment days will be separated by 1 week to reduce carryover effect. To increase power, each subject will undergo two DSR treatment days and 1 placebo day, with the placebo day selected randomly from among the three treatment days, in counter balanced order. Treatment assignment (drug and SBR) will be double blinded. Follow-up cognitive and safety measures will also be completed on the final treatment day.

BEHAVIORAL

Sensory Based remediation paradigm

Every subject will receive sensory based remediation on each treatment visit: Three 80-tone pair blocks will be used per session (\~1 hour with breaks). To minimize practice effects, we will use a different base tone for each treatment day (e.g. 500, 1000, and 2000 Hz), also in a randomized counter-balanced order. To assess the improvement over a treatment day, we will record the ratio of the frequencies in all tone pairs. To correct this non-normal distribution we take the natural log of each of these ratios to determine the tone matching threshold.

Sponsors & Collaborators

• Columbia University

  collaborator OTHER

• Nathan Kline Institute for Psychiatric Research

  lead OTHER

Principal Investigators

• Joshua T Kantrowitz, MD · Columbia University/Nathan Kline Institute

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

QUADRUPLE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

64 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2012-03-31

Primary Completion

2013-06-30

Completion

2013-06-30

Countries

• United States

Study Locations