title: Energy-Efficient Information Transfer by Visual Pathway Synapses.
abstract: The architecture of computational devices is shaped by their energy consumption. Energetic constraints are used to design silicon-based computers but are poorly understood for neural computation. In the brain, most energy is used to reverse ion influxes generating excitatory postsynaptic currents (EPSCs) and action potentials. Thus, EPSCs should be small to minimize energy use, but not so small as to impair information transmission. We quantified information flow through the retinothalamic synapse in the visual pathway in brain slices, with cortical and inhibitory input to the postsynaptic cell blocked. Altering EPSC size with dynamic clamp, we found that a larger-than-normal EPSC increased information flow through the synapse. Thus, the evolutionarily selected EPSC size does not maximize retinal information flow to the cortex. By assessing the energy used on postsynaptic ion pumping and action potentials, we show that, instead, the EPSC size optimizes the ratio of retinal information transmitted to energy consumed. These data suggest maximization of information transmission per energy used as a synaptic design principle.
authors.affiliation: Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Julia J
authors.initials: JJ
authors.lastname: Harris
authors.affiliation: Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Renaud
authors.initials: R
authors.lastname: Jolivet
authors.affiliation: Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Engl
authors.affiliation: Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK. Electronic address: d.attwell@ucl.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Attwell
mesh_terms: D004734:Energy Metabolism; D019706:Excitatory Postsynaptic Potentials; D014795:Visual Pathways / Q000502:physiology*