Unlocking 'silent synapses' in the brain could improve learning ability

It is a melancholic fact of life that as we get older, it gets harder to learn new things. Adults typically have more trouble picking up new languages and musical instruments than children, however new research into the brain could offer insights into how to learn more efficiently with age. It has been discovered that so-called silent synapses in the brain are kept in reserve in case new things are needed to be learned in later life. These secretive neurons may be turned on artificially using electrical currents, to reinduce plasticity in the adult brain.

Learning results in the changes of neural pathways as new connections are made in the brain. Each connection between a nerve cell is called a synapse, where messages travel through gaps in the form of molecules called neurotransmitters.The human brain is the most complex organ on Earth, with more than 600 trillion synapses sending signals across a vast and intricate network.

Researchers at the Massachusetts Institute of Technology recently published an article in Nature magazine, stating that silent synapses remain present in adult brains as dormant neurons that lie ready and waiting, until the adult needs to learn something new.

Conventional neuroscience assumed that these disappeared from the brain as it matured, however, this new research suggests that not only they are present in adulthood, but they are present in large quantities. In adult mice, one-quarter of neural brain samples were found to contain silent synapses, with mice brains being sufficiently similar to human ones to the point where the same levels could be applied to our own minds.

In the future, being able to activate these silent synapses artificially could have significant implications for how we learn new skills. Researchers have confirmed that, in theory, it is possible to activate them to turn into functioning synapses, by releasing glutamate, along with a surge of electricity.

Within minutes of this happening, the synapse displayed signs of communicating with receptor molecules, and when the same treatment was applied to mature synapses, no response occurred. This indicated that it is possible to unsilence and improve plasticity of dormant brain tissue, at least in a laboratory setting. On the flipside, the experiment also confirmed the resilience of mature synapses to change, with neurons requiring a much higher threshold of electrical charge and glutamate to change. This makes sense when considering the importance of adult brains to maintain current important information without it being overwritten.

Proving that this level of tinkering is possible in the mammalian brain is a big jump in our understanding of the human brain. As well as offering a deeper understanding of how we can improve learning in later life, the research also promises new ways in which we can treat degenerative diseases of the brain such as Alzheimer's, where the capacity to function and learn is greatly impaired.

Such research is still very much in the early stages of development, however, and for now, any adults who wish to learn something new will have to achieve it through old-fashioned hard work, repetition and discipline.

Barry He is a London-based columnist for China Daily.