New Findings Reveal Separate Synaptic Transmission Sites Drive Brain Plasticity

Recent research from the University of Pittsburgh challenges long-held beliefs about neural communication and plasticity by demonstrating that the brain utilizes distinct transmission sites to regulate different types of synaptic activity. Published in Science Advances, the study shows that spontaneous and evoked synaptic transmissions, once thought to originate from a shared synaptic site, are actually mediated through separate, specialized regions within the synapse.

Traditionally, scientists believed that both spontaneous signals—those occurring randomly—and evoked signals—triggered by sensory input or experience—were governed by the same molecular machinery located at a canonical synaptic site. However, using advanced imaging techniques and pharmacological interventions in a mouse model, the researchers observed divergent developmental trajectories of these two signaling modes, especially after the onset of visual experience.

As visual input increased, evoked transmission—the process linked to learning and active response—continued to strengthen, whereas spontaneous activity plateaued, suggesting differential control mechanisms. When the team introduced chemicals to activate silent receptors on postsynaptic neurons, spontaneous activity surged without affecting evoked transmission. This evidence indicates that these two types of signaling are processed through separate structural and functional synaptic regions.

This separation likely enables the brain to stabilize background neural activity via spontaneous signaling while selectively reinforcing pathways involved in learning through evoked activity. Such an organizational strategy might be crucial for maintaining homeostasis while allowing adaptive plasticity.

Understanding these distinct pathways offers significant insights into neurological and psychiatric disorders. Abnormal synaptic transmission has been linked to conditions such as autism, Alzheimer’s disease, and substance use disorders. By elucidating how the healthy brain manages different signaling modes, scientists can better identify what goes wrong in these illnesses.

"Our findings highlight a fundamental organizational principle of the brain," said Yue Yang, the study’s lead author. "Separating these transmission sites allows the brain to stay stable yet adaptable—an essential balance for learning and memory."

This research advances our comprehension of neural connectivity and may direct future therapies for disorders related to synaptic dysfunction.

Source: https://medicalxpress.com/news/2025-06-distinct-transmission-sites-upend-decades.html