Sunday, December 04, 2022

Silent synapses are abundant in the adult brain allowing learn like an adolescent into late age

Good news! This could be a major game changer! 

Another nice example, where the majority of scientists has been dead wrong for decades! Soon, we will probably learn that the so called settled science on Global Warming/Climate Change shares the same fate! 😊

"... neuroscientists have discovered that the adult brain contains millions of “silent synapses” — immature connections between neurons that remain inactive until they’re recruited to help form new memories.
Until now, it was believed that silent synapses were present only during early development, when they help the brain learn the new information that it’s exposed to early in life. However, the new ... study revealed that in adult mice, about 30 percent of all synapses in the brain’s cortex are silent.
The existence of these silent synapses may help to explain how the adult brain is able to continually form new memories and learn new things without having to modify existing conventional synapses, the researchers say. ...
When scientists first discovered silent synapses decades ago, they were seen primarily in the brains of young mice and other animals. During early development, these synapses are believed to help the brain acquire the massive amounts of information that babies need to learn about their environment and how to interact with it. In mice, these synapses were believed to disappear by about 12 days of age (equivalent to the first months of human life). ..."

From the abstract:
"Newly generated excitatory synapses in the mammalian cortex lack sufficient AMPA-type glutamate receptors to mediate neurotransmission, resulting in functionally silent synapses that require activity-dependent plasticity to mature. Silent synapses are abundant in early development, during which they mediate circuit formation and refinement, but they are thought to be scarce in adulthood. However, adults retain a capacity for neural plasticity and flexible learning that suggests that the formation of new connections is still prevalent. Here we used super-resolution protein imaging to visualize synaptic proteins at 2,234 synapses from layer 5 pyramidal neurons in the primary visual cortex of adult mice. Unexpectedly, about 25% of these synapses lack AMPA receptors. These putative silent synapses were located at the tips of thin dendritic protrusions, known as filopodia, which were more abundant by an order of magnitude than previously believed (comprising about 30% of all dendritic protrusions). Physiological experiments revealed that filopodia do indeed lack AMPA-receptor-mediated transmission, but they exhibit NMDA-receptor-mediated synaptic transmission. We further showed that functionally silent synapses on filopodia can be unsilenced through Hebbian plasticity, recruiting new active connections into a neuron’s input matrix. These results challenge the model that functional connectivity is largely fixed in the adult cortex and demonstrate a new mechanism for flexible control of synaptic wiring that expands the learning capabilities of the mature brain."

Silent synapses are abundant in the adult brain | MIT News | Massachusetts Institute of Technology These immature connections may explain how the adult brain is able to form new memories and absorb new information.


Researchers have discovered that the adult mouse brain contains millions of silent synapses, located on tiny structures called filopodia.

Fig. 1: Filopodia account for a large fraction of dendritic protrusions in L5 and L2/3 pyramidal neurons of adult mouse primary visual cortex.


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