Specific networks in brain present much earlier than previously thought

The cerebral cortex in humans and carnivores has a very precise special organization that involves networks of neurons. Composed of thousands of neurons distributed over millimeters of the cortical surface, distributed networks play a critical role in all aspects of brain function including the processing of complex sensory input.

"Not only are these large scale networks present much earlier than we thought, but they predict future function," said Gordon Smith, PhD., Department of Neuroscience at the University of Minnesota Medical School. "What that suggests is that events happening early in development are setting the stage for what we see later in life."

In a study published in Nature Neuroscience, researchers used calcium imaging techniques to visualize with unprecedented resolution spontaneous activity patterns in the mature visual cortex. While they expected to see widespread patterns of activity, they hadn't anticipated the high degree of precision they observed in the network interactions. The spontaneous network activity patterns were so highly correlated that the activity of small populations of neurons could reliably predict coincident network activity patterns millimeters away, and these correlation patterns beautifully predicted the patterns of network activity evoked by visual stimulation.

When they looked earlier in development prior to eye opening, they discovered robust long-range patterns of correlated spontaneous activity that extended over distances comparable to what was seen in the mature brain.

"This was surprising, since connectivity in the brain is very immature at this point in development," said Smith, whose work on this study was done both at the Max Planck Florida Institute and the University of Minnesota. "This finding led us to propose a novel computational model of the early visual cortex that can replicate these findings." The model shows that at early stages in development, long-range network activity can be generated by activity patterns spreading through chains of local cortical connections.

Future studies will test the prediction that activity dependent plasticity mechanisms shape the structure of long-range connections based on the instructive activity patterns derived from local cortical connections. Smith is currently furthering this research at the University of Minnesota.