LAUSR

BACKGROUND Patients with post-acute anti-N-methyl-D-aspartate (anti-NMDA) receptor encephalitis are often left with permanent memory impairments. Given that NMDA receptors are essential to memory encoding, and encoding processes have been suggested to contribute to the success of memory retrieval, we investigate whether post-acute anti-NMDA receptor encephalitis leads to abnormal brain activation during verbal memory encoding and its potential effects on subsequent memory retrieval performance. METHODS To address this issue, this study recruited twenty-one adult patients with anti-NMDA receptor encephalitis past the acute stage and twenty-two healthy controls (HCs). Functional magnetic resonance imaging (fMRI) data were collected when they completed an episodic memory task. RESULTS At the neural level, the patients showed higher brain activation than the HCs in the bilateral hippocampus/parahippocampus (HG/PHG), right superior temporal gyrus (STG) and right thalamus during memory encoding. At the behavioural level, the patients showed worse memory retrieval performance than the HCs. Importantly, greater brain activation in the left HG/PHG during memory encoding was significantly associated with worse memory retrieval performance among the patients. CONCLUSION Our findings indicate that post-acute anti-NMDA receptor encephalitis is likely related to altered brain activation during memory encoding. Particularly, less memory retrieval performance often observed in patients with post-acute anti-NMDA receptor encephalitis may result from abnormal activation in hippocampus during encoding. These observations may enhance our understanding of NMDA receptor dysfunction in the human brain.