Scientists in Italy report they have found that decreased functional connectivity in the brain can be caused by microglial cells that do not trim connections between neurons. They believe their findings shed light on why different parts of the brain do not communicate with each other in diseases like autism and other neurodevelopmental disorders.

“We show that a deficit in microglia during development [in mice] can have widespread and long-lasting effects on brain wiring and behavior,” said Cornelius Gross, Ph.D., the European Molecular Biology Laboratory deputy head of outstation and senior scientist who led the study.

His team, along with collaborators at the Istituto Italiano di Tecnologia and La Sapienza University, published their study (“Deficient neuron-microglia signaling results in impaired functional brain connectivity and social behavior”) in Nature Neuroscience.

The findings indicate that, by trimming surplus connections in the developing brain, microglia allow the remaining links to grow stronger, like high-speed fiber-optic cables carrying strong signals between brain regions, explained Dr. Gross.

But if these cells fail to do their job at that crucial stage of development, those brain regions are left with a weaker communication network, which in turn has lifelong effects on behavior.

“Mice lacking the chemokine receptor Cx3cr1 exhibit a transient reduction of microglia during the early postnatal period and a consequent deficit in synaptic pruning,” write the investigators. “We show that deficient synaptic pruning is associated with weak synaptic transmission, decreased functional brain connectivity, deficits in social interaction, and increased repetitive-behavior phenotypes that have been previously associated with autism and other neurodevelopmental and neuropsychiatric disorders.”

According to Dr. Gross, “This is an exciting time to be studying microglia.… They’re turning out to be major players in how our brain gets wired up.”

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