caa a22 4500 397581696 CHVBK 20180308164909.0 cr unu---uuuuu 161202e199603 xx s 000 0 eng 10.1093/cercor/6.2.93 doi (NATIONALLICENCE)oxford-10.1093/cercor/6.2.93 A Brief History of Time (Constants) [Elektronische Daten] [Christof Koch, Moshe Rapp, Idan Segev] That the cerebral cortex processes information at prodigious speeds cannot be doubted. Yet the passive time constant, τm$$$ of neurons, often thought of as a measure of the neuron's "response time” to synaptic input, is relatively long. In the 1950s, τm was estimated to be only a few milliseconds for mammalian central neurons; with improvement in recording techniques, its estimated value grew over the years and it now stands near 20-100 msec. However, as we will argue here, the functional meaning of τm is ambiguous. On the basis of a newly introduced definition of local delay, we show that the time window for synaptic integration in passive dendritic trees can be much smaller than the time constant. We argue that the voltage response to very brief synaptic inputs is essentially independent of τm. We discuss how τm can change dynamically with the global activity of the network, as well as the difficulties of defining a time constant in structures with voltage-dependent elements. We conclude that the classically defined τm only provides a very rough estimate, typically an overestimate, of the response time of neurons and that alternative measures are required to capture the dependency of the time course of the membrane potential on ligand-gated and/or voltage-dependent membrane conductances. © 1996 Oxford University Press Feature Article nationallicence Koch Christof Computation and Neural Systems Program, California Institute of Technology Pasadena, California 91125 aut Rapp Moshe Department of Neurobiology, Institute of Life Sciences and Center for Neural Computation, Hebrew University Jerusalem 91904, Israel aut Segev Idan Department of Neurobiology, Institute of Life Sciences and Center for Neural Computation, Hebrew University Jerusalem 91904, Israel aut Cerebral Cortex Oxford University Press 6/2(1996-03), 93-101 1047-3211 6:2<93 1996 6 cercor https://doi.org/10.1093/cercor/6.2.93 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/cercor/6.2.93 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Koch Christof Computation and Neural Systems Program, California Institute of Technology Pasadena, California 91125 aut NATIONALLICENCE 700 1- Rapp Moshe Department of Neurobiology, Institute of Life Sciences and Center for Neural Computation, Hebrew University Jerusalem 91904, Israel aut NATIONALLICENCE 700 1- Segev Idan Department of Neurobiology, Institute of Life Sciences and Center for Neural Computation, Hebrew University Jerusalem 91904, Israel aut NATIONALLICENCE 773 0- Cerebral Cortex Oxford University Press 6/2(1996-03), 93-101 1047-3211 6:2<93 1996 6 cercor Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford