NMDAR antibodies are proteins produced by the immune system that mistakenly target and attack the N-methyl-D-aspartate receptor (NMDAR) in the brain. These receptors are crucial for synaptic plasticity, learning, and memory. When NMDAR antibodies bind to these receptors, they can disrupt normal brain function, leading to various neurological and psychiatric symptoms. The presence of NMDAR antibodies is associated with a condition known as anti-NMDAR encephalitis, which can cause symptoms such as seizures, confusion, and changes in behavior. Diagnosis typically involves testing for these antibodies in the blood or cerebrospinal fluid, and treatment often includes immunotherapy to reduce antibody levels and alleviate symptoms.