Dragoi publishes research on brain synergy

For the past century, neuroscientists have strived to identify the organizing principles of brain function. One important idea that has influenced the field tremendously is that neurons in the brain exhibit redundancy in their code, which allows neighboring cells in the same part of the brain to complete the same task. Redundancy can be extremely beneficial, especially in cases of neuronal loss, where nearby neurons are able to take over the function of dying cells to ensure that the system can survive.

Valentin Dragoi, PhD, Rochelle and Max Levit Distinguished Professor in the Neurosciences, Neurobiology and Anatomy, Sunny Nigam, PhD, and Sorin Pojoga, PhD, postdoctoral fellows in the Dragoi Lab, performed pioneering research in primary visual cortex to discover an additional operating principle in the brain, namely synergistic coding. That is, the whole is greater than the sum of its parts – groups of two or more neurons can jointly transmit more information about the world than the sum of the information transmitted by each neuron independently.

“We found that redundancy may not be as prominent as commonly believed,” Dragoi said.

Dragoi, Nigam, and Pojoga, PhD, have had their paper, “Synergistic Coding of Visual Information in Columnar Networks,” published in Neuron.

Most previous studies have focused on neuronal recordings across tangential regions spanning the surface of the brain. However, the study in Dragoi’s lab went below the surface along a cortical column.

“From a functioning standpoint, redundancy appears to not be such an efficient principle or mechanism, because you have many cells doing the same thing,” Dragoi said. “You want them to be independent and carry different functions.  There is another fundamental principle which is equally important, or maybe more important, which is called synergy.”

Dragoi said one could think about redundancy and synergy in the context of a football game. Redundancy may be thought as a team made up of the best players, but the players are all doing the same thing. Synergy, on the other hand, can be compared to the team that has weaker players, but with different talents and cooperation, making them the better team.

“The brain is composed of large networks of cells,” Dragoi said. “So when you have the synergy principle working, you can extract more information than when you have redundant interactions. Importantly, we discovered that there are specialized neurons that predominantly engage in synergistic interactions, whereas other neurons engage in predominantly redundant interactions, and this arrangement has important implications for the way in which networks of cells efficiently extract information from the environment.”

Their research showed that neuronal populations consisting of only synergy hubs were significantly better at decoding information compared to populations consisting of only redundancy hubs or both redundancy and synergy hubs.

The study in Dragoi’s lab was funded from grants from the NIH EUREKA Program and the National Eye Institute. Their work can further the understanding of the language of brain cells and the operating principles that allow them to encode sensory information to subsequently influence behavior. Dragoi said he plans to extend these investigations in other brain areas outside the primary visual cortex to examine the generality of synergistic coding and how it relates to attention, learning, and memory.