Dynamic electrical synapses for a new form of plasticity and relentless activities of the brain

What is it about?

Brain activities are relentless, from the first to the last day of life. Moreover, our thoughts are ever-changing. Flight of ideas is a common daily experience. A fundamental yet long-term unanswered question in neurobiology is how the brain activities could be persistent when an extrinsic trigger is over. Mammalian intelligence as well as epileptogenesis is chiefly based in the telencephalic networks built by interconnected excitatory (or pyramidal, PNs) and inhibitory neurons (INs). It was hard to envisage how such a negative feedback system could accommodate such autonomous and wildly changing neural discharges necessary for intellectual processing and epileptogenesis. We demonstrate that INs can not only inhibit PNs with chemical messengers, but also excite PNs with intercellular electrical synapses. The unparalleled design makes the circuitry not dominated by negative feedback loops, but powered by self-supplied trigger for non-stop oscillating activities. Most importantly, the deployment of the electrical synapses is highly dynamic and dependent on activities in corresponding neurons. This crafts an unprecedented form of context-dependent plasticity in the telencephalon, which enables spatiotemporal potentiation to support specific patterns of automatic oscillating discharges and thus learning, memory, inspiration, determination, and also seizures if carried too far.

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Photo by Steve Johnson on Unsplash

Photo by Steve Johnson on Unsplash

Why is it important?

The sensorimotor integration and essentially all of the cognitive processes are dependent on automatic oscillating discharges of the brain after the initial trigger. We found that such automatic “afterdischarges” are powered and modulated by the dynamic electrical synapses between INs and PNs, making ever-changing and highly adaptable brain circuitries based on the past experiences as well as the ongoing events. Epileptic seizures or a wide spectrum of clinical disorders could in essence be an abnormal extension of this fundamental operational rationale of the system.