Spontaneous brain activity drives connections between neurons

Spontaneous activity in the developing brain fine-tunes the plasticity of the synapses. That is the conclusion of a study by the Academy’s Netherlands Institute for Neuroscience published in the authoritative journal Neuron on 15 July. The discovery by PhD candidate Johan Winnubst and his colleagues offers new insights into developmental disorders in which neural connections are disrupted, such as autism and schizophrenia.

While the young brain is developing, many brain areas generate their own internal, spontaneous activity, with large groups of neurons all becoming active at the same time. The synchrony between active groups of cells is important for the formation of synapses, the connections between neurons that carry information from one neuron to the next. The formation of the right synapses during brain development is vital to the brain’s functioning later on.

The study, carried out by the Department of Synapse and Network Development at the Netherlands Institute for Neuroscience, shows that synapses that tend to be asynchronous with neighboring synapses are depressed. ‘This is because asynchronous synapses function less effectively over time,’ explains neuroscientist Winnubst. ‘That finding has led us to conclude that spontaneous brain activity drives the clustering of synapses that convey the same information.’

Earlier research

Earlier research by the Netherlands Institute for Neuroscience revealed that neighboring synapses on the same cell often display more synchronous spontaneous activity than synapses that are located farther apart. The assumption was that this form of ‘synaptic clustering’ was vital to a cell’s ability to process information later on and that cells that developed without spontaneous activity would lack such synaptic clustering.

Winnubst and his colleagues wanted to know which mechanism is responsible for clustering between co-active synapses. They therefore tracked the spontaneous activity of large groups of synapses on individual brain cells of live mice using calcium microscopy and electrophysiology, a new approach in this line of research.

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