The specific aim of this project is to test if memantine will influence the ERPs change, as in healthy subjects, in patients with early schizophrenia. The specific study population is been known of just have their first episode psychosis subsided, conventionally defined by significantly improved positive symptoms, yet some of them complaining of cognitive decline or presenting with persistent negative symptoms. Previous study showed improvement in mismatch negativity was correlated with general function improvement in schizophrenia. Although a recent study failed to demonstrate positive effects on residual psychopathology of a group of chronic stable schizophrenic patients. In this study we are targeting at a specific population of early schizophrenic patients to examine the efficacy of memantine on neurobiological markers and possible application to general psychopathology. Our objectives include: