Pattern completion, the ability to retrieve complete memories initiated by partial cues, is a critical feature of the memory process.However, little is known regarding the molecular and cellular mechanisms underlying this process.To study the role of dopamine in memory recall, we have analyzed dopamine transporter heterozygous knockout mice (DAT+/2), and found that while these mice possess normal learning, consolidation, and memory recall under full cue conditions, they exhibit specific deficits in pattern completion under partial cue condition.This form of memory recall deficit in the dopamine transporter heterozygous knockout mice can be reversed by a low dose of the dopamine antagonist haloperidol, further confirming that the inability to retrieve memory patterns is a result of dopamine imbalance.Therefore, our results reveal that a delicate control of the brain's dopamine level is critical for pattern completion during associative memory recall.