A new study from Pitt researchers challenges a decades-old assumption in neuroscience by showing that the brain uses distinct transmission sites — not a shared site — to achieve different types of plasticity. Neurons communicate through a process called synaptic transmission, where one neuron releases chemical messengers called neurotransmitters from a presynaptic terminal. In contrast, spontaneous transmissions plateaued, suggesting that the brain applies different forms of control to the two signaling modes. This division likely enables the brain to maintain consistent background activity through spontaneous signaling while refining behaviorally relevant pathways through evoked activity. Abnormalities in synaptic signaling have been linked to conditions like autism, Alzheimer’s disease and substance use disorders.