Understanding information processing in the brain requires us to monitor
neural activity at high spatiotemporal resolution. Using an ultrafast two-photon
fluorescence microscope (2PFM) empowered by all-optical laser scanning, we
imaged neural activity
in vivo
at up to 3,000 frames per second
and submicron spatial resolution. This ultrafast imaging method enabled
monitoring of both supra- and sub-threshold electrical activity down to 345
μm below the brain surface in head-fixed awake mice.
Dendritic integration of synaptic inputs mediates rapid neural computation as well as longer-lasting plasticity. Several channel types can mediate dendritically initiated spikes (dSpikes), which may impact information processing and storage across multiple timescales; however, the roles of different channels in the rapid vs long-term effects of dSpikes are unknown. We show here that dSpikes mediated by Nav channels (blocked by a low concentration of TTX) are required for long-term potentiation (LTP) in the distal apical dendrites of hippocampal pyramidal neurons. Furthermore, imaging, simulations, and buffering experiments all support a model whereby fast Nav channel-mediated dSpikes (Na-dSpikes) contribute to LTP induction by promoting large, transient, localized increases in intracellular calcium concentration near the calcium-conducting pores of NMDAR and L-type Cav channels. Thus, in addition to contributing to rapid neural processing, Na-dSpikes are likely to contribute to memory formation via their role in long-lasting synaptic plasticity.DOI:
http://dx.doi.org/10.7554/eLife.06414.001
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