Active membrane conductances and morphology of a collision detection neuron broaden its impedance profile and improve membrane synchrony

Our brain processes information through the coordinated efforts of billions of individual neurons, each of which transforms a small part of the overall information stream. Central to this is how neurons integrate and transform complex patterns of synaptic inputs. The neuronal membrane impedance determines the change in membrane potential in response to input currents, and therefore sets the gain and timing for synaptic integration. Using single and dual dendritic recordings in vivo , pharmacology, and computational modeling, we characterized the role of two active conductances gH and gM, meditated respectively by hyperpolarization-activated cyclic nucleotide gated (HCN) channels and by muscarine sensitive M-channels, in shaping the membrane impedance of a collision detection neuron in female Schistocerca americana grasshoppers. The neuron is known by its acronym LGMD, which stands for lobula giant movement detector. In contrast to other neurons where these conductances have been studied, we found that gH and gM promote broadband, synchronous integration over the LGMD's functional range of membrane potentials and input frequencies. Additionally, we found that the branching morphology of the LGMD helped increase both the gain and...Continue Reading