Post: Silent Synapses

Key points

Silent synapses are dormant neural connections that can be activated for memory formation.

BDNF acts as a critical mediator in transforming silent synapses during development and learning.

Ketamine rapidly activates silent synapses by increasing BDNF, explaining its fast antidepressant effects.

Co-written with Jai Liester.

Silent synapses represent one of neuroscience’s most fascinating discoveries—connections between neurons that lie dormant until activated by specific triggers. These mysterious structures have revolutionized our understanding of brain plasticity and development while opening new therapeutic avenues for various neuropsychiatric conditions. Silent synapse Source: ChatGPT/DALL·E The Discovery of Silent Synapses

The concept of silent synapses emerged in the early 1990s when researchers observed something peculiar during experiments on learning and memory . Roberto Malinow and colleagues at the University of California noted that certain synapses appeared functionally inactive under normal conditions but could be "awakened.” These synapses were dubbed "silent" because they lacked a specific type of receptor known as “AMPA receptors,” to which glutamate binds. Evolution of Understanding

Initially, silent synapses were viewed primarily as developmental phenomena, abundant in the developing brain but diminishing with age. Researchers found that up to 80% of excitatory synapses in the hippocampus—a critical structure for learning and memory—of newborns may be silent, compared to fewer than 30% in adulthood.

As investigation continued through the 2000s, scientists recognized that silent synapses persist in the adult brain, though at lower levels. Their presence suggests a reservoir of potential connections that can be activated when needed, serving as "blank slates" for new memory formation.Our understanding evolved further when researchers discovered that synapse silencing is bidirectional—active synapses can become silent, essentially creating a storage bank of previous connections that can be reactivated later.By the 2010s, research demonstrated that silent synapses play crucial roles in neuroplasticity, addiction , and recovery from brain injury. Work at Johns Hopkins further highlighted how silent synapse activation contributes to the extinction of fear memory and potentially PTSD treatment. The Critical Role of BDNF in Silent Synapse Activation Brain-derived neurotrophic factor (BDNF) has emerged as a key player in the activation of silent synapses. This […]

Silent Synapses