Silent Synapses in the Adult Brain

The formation of new synapses, the connections between neurons, is the critical step for neural circuit assembly. Newly formed glutamatergic synapses are initially silent and require activity-dependent plasticity to become fully functional connections. While these synapses have long been considered a vital part of the developmental program for neural networks, recent findings now indicate that silent synapses are a key source of neural circuit plasticity in the adult brain. Here, we review current evidence for silent synapses in the adult brain and explore the potential roles of these highly plastic structures. We argue that silent synapses may be instrumental in adult neural circuit remodeling and can serve as a latent reservoir of plasticity that enhances information processing and storage. This previously underappreciated aspect of adult plasticity underscores the need for innovative approaches and further investigation into the dynamic contribution of silent synapses to learning and memory in the adult brain.