Objective:

The abnormality of mismatch negative (MMN) in schizophrenia is thought to be associated with perceptional disturbance and cognitive dysfunction. And the antagonists of the N-methyl-D-aspartate (NMDA) receptors, ketamine, can induce anomalies of psychophysiology and cognitive function as those of schizophrenia. In order to explore the role of NMDA receptors on echoic memory system, MMN under ketamine administration was analyzed.

Methods:

MMNs of Healthy 12 subjects under subanesthetic dose (0.65 ㎎/㎏/hr) of ketamine administration in placebo-controlled design were recorded by 128 channel EEG. Brief Psychiatric Rating Scale (BPRS) change was also evaluated.

Results:

BPRS score was significantly increased by ketamine administration (t=-6.655, p<0.005). Ketamine induced significant decrease in MMN amplitudes (Fz, t=-2.572, p=0.026). Neither MMN amplitude under placebo administration nor MMN latencies under ketamine administration and placebo was changed significantly.

Conclusion:

Ketamine induced echoic memory dysfunction in healthy subjects, which is usually found in schizophrenic patients. Consequently, reduced glutamatergic activity in brain could be involved some early processes of the memory dysfunction in schizophrenia.