{'fraction_non_alphanumeric': 0.01673101673101673, 'fraction_numerical': 0.0045045045045045045, 'mean_word_length': 5.790393013100437, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Energy-Efficient Action Potentials in Hippocampal Mossy Fibers

Minimizing Brain Energy Consumption How much energy is actually required to generate neuronal activity and information processing? By combining direct recordings at physiological temperatures from mossy fiber axons in rat brain slices with modeling and simulation approaches, Alle et al. (p. 1405; see the Perspective by Magistretti) found that the regenerative action potentials in nonmyelinated axons of mammalian hippocampus are remarkably energy efficient. The data indicate a surprisingly minor contribution of action potentials to the entire energy expenditure of neural information processing. Mammalian neurons have developed highly efficient ways to limit energy consumption while propagating neuronal information. Action potentials in nonmyelinated axons are considered to contribute substantially to activity-dependent brain metabolism. Here we show that fast Na+ current decay and delayed K+ current onset during action potentials in nonmyelinated mossy fibers of the rat hippocampus minimize the overlap of their respective ion fluxes. This results in total Na+ influx and associated energy demand per action potential of only 1.3 times the theoretical minimum, in contrast to the factor of 4 used in previous energy budget calculations for neural activity. Analysis of ionic conductance parameters revealed that the properties of Na+ and K+ channels are matched to make axonal action potentials energy-efficient, minimizing their contribution to activity-dependent metabolism.