NMDA stands for N-Methyl-D-Aspartate, which is a specific type of receptor in the brain. These receptors play a crucial role in synaptic plasticity, a process that is essential for learning and memory. They are activated by the neurotransmitter glutamate, which is the most abundant excitatory neurotransmitter in the brain. NMDA receptors are unique because they require two conditions to be activated: binding of glutamate and a change in voltage across the cell membrane. This dual requirement allows them to act as molecular coincidence detectors, meaning they help the brain process information by responding only when certain conditions are met.