title: Subthreshold voltage noise of rat neocortical pyramidal neurones.
abstract: Neurones are noisy elements. Noise arises from both intrinsic and extrinsic sources, and manifests itself as fluctuations in the membrane potential. These fluctuations limit the accuracy of a neurone's output but have also been suggested to play a computational role. We present a detailed study of the amplitude and spectrum of voltage noise recorded at the soma of layer IV-V pyramidal neurones in slices taken from rat neocortex. The dependence of the noise on holding potential, synaptic activity and Na+ conductance is systematically analysed. We demonstrate that voltage noise increases non-linearly as the cell depolarizes (from a standard deviation (s.d.) of 0.19 mV at -75 mV to an s.d. of 0.54 mV at -55 mV). The increase in voltage noise is accompanied by an increase in the cell impedance, due to voltage dependence of Na+ conductance. The impedance increase accounts for the majority (70%) of the voltage noise increase. The increase in voltage noise and impedance is restricted to the low-frequency range (0.2-2 Hz). At the high frequency range (5-100 Hz) the voltage noise is dominated by synaptic activity. In our slice preparation, synaptic noise has little effect on the cell impedance. A minimal model reproduces qualitatively these data. Our results imply that ion channel noise contributes significantly to membrane voltage fluctuations at the subthreshold voltage range, and that Na+ conductance plays a key role in determining the amplitude of this noise by acting as a voltage-dependent amplifier of low-frequency transients.
authors.affiliation: Department of Neurobiology, The Hebrew University, Jerusalem 91904, Israel.
authors.forename: Gilad A
authors.initials: GA
authors.lastname: Jacobson
authors.forename: Kamran
authors.initials: K
authors.lastname: Diba
authors.forename: Anat
authors.initials: A
authors.lastname: Yaron-Jakoubovitch
authors.forename: Yasmin
authors.initials: Y
authors.lastname: Oz
authors.forename: Christof
authors.initials: C
authors.lastname: Koch
authors.forename: Idan
authors.initials: I
authors.lastname: Segev
authors.forename: Yosef
authors.initials: Y
authors.lastname: Yarom
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D008954:Models, Biological; D019579:Neocortex / Q000187:drug effects / Q000502:physiology*; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
chemical_list: D011810:Quinoxalines; D015222:Sodium Channels; C056723:FG 9041