The “circuit” metaphor of the brain is as indisputable as it is familiar: Neurons forge direct physical connections to create functional networks, for instance to store memories or produce thoughts. But the metaphor is also incomplete. What drives these circuits and networks to come together? New evidence suggests that at least some of this coordination comes from electric fields.
The new study in Cerebral Cortex shows that as animals played working memory games, the information about what they were remembering was coordinated across two key brain regions by the electric field that emerged from the underlying electrical activity of all participating neurons. The field, in turn, appeared to drive the neural activity, or the fluctuations of voltage apparent across the cells’ membranes.
If the neurons are musicians in an orchestra, the brain regions are their sections, and the memory is the music they produce, the study’s authors said, then the electric field is the conductor.
The physical mechanism by which this prevailing electric field influences the membrane voltage of constituent neurons is called “ephaptic coupling.” Those membrane voltages are fundamental to brain activity. When they cross a threshold, neurons “spike,” sending an electrical transmission that signals other neurons across connections called synapses. But any amount of electrical activity could contribute to a prevailing electric field which also influences the spiking, said study senior author Earl K. Miller, Picower Professor in the Department of Brain and Cognitive Sciences at MIT.
