Scientists have now observed how the brain’s place cells stave off inhibitory input in the process of establishing their tuning to specific locations. The study shows that signaling by endocannabinoids is required.
Knowing where you are is so important, the brain has special cells that dedicate themselves to the purpose. In a recent study in Science, a team of neuroscientists has demonstrated in live behaving animals a long-hypothesized mechanism that such “place cells” employ to refine that sense of location.
When place cell’s become activated at their target location they emit an endocannabinoid chemical signal to suppress the incoming circuit connections, called “synapses,” of a specific type of inhibitory neuron. If the scientists disrupted the endocannabinoid signaling during this process, place cells would lose their ability to refine their tuning to the location, making their sense of place less accurate.
Previous studies had only showed this particular way of altering neural circuit communication, or “synaptic plasticity,” in tissue slices rather than during actual spatial navigation behavior, said co-lead author Linlin Fan, assistant professor in The Picower Institute for Learning and Memory and the Department of Brain and Cognitive Sciences at MIT. Showing that this plasticity, called “depolarization-induced suppression of inhibition” (DSI) is key to refining memory of locations required multiple cutting-edge methods, she said. The emerging tools allowed the team, based at Stanford University at the time, to literally see and control the electrical activity of the circuit and to visualize the endocannabinoid signals.
