See termination reason in detailed description.

To evaluate whether PF-02545920 reduces the effects of ketamine on brain activation during causal learning as measured by fMRI compared to placebo in healthy human subjects, and to evaluate whether behavioral measures of abnormal causal learning under ketamine are reduced by treatment with PF 02545920.

The study was terminated on November 2, 2012 due to a reassessment of the likelihood of the study meeting its scientific objectives in light of data with the investigational drug obtained from another clinical study. The decision to terminate the trial was not based on any safety concerns.

Inclusion Criteria:

• Healthy male and/or female subjects between the ages of 21 and 45 years, inclusive. Body Mass Index (BMI) of 17.5 to 30.5 kg/m2; and a total body weight >50 kg (110 lbs). (Healthy is defined as no clinically relevant abnormalities identified by a detailed medical history, full physical examination, including blood pressure and pulse rate measurement, 12 lead ECG and clinical laboratory tests).
• Right handed as determined by handedness questionnaire.
• Able to read and write English as a primary language.

Exclusion Criteria:

• Female subjects who are pregnant or breastfeeding.
• Any evidence of significant psychosis-like symptoms.
• Known sensitivity to ketamine.