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Rony Azouz and Charles M. Gray
SummarySeveral theories have proposed a functional role for response synchronization in sensory perception. Critics of these theories have argued that selective synchronization is physiologically implausible when cortical networks operate at high levels of activity. Using intracellular recordings from visual cortex in vivo, in combination with numerical simulations, we find dynamic changes in spike threshold that reduce cellular sensitivity to slow depolarizations and concurrently increase the relative sensitivity to rapid depolarizations. Consistent with this, we find that spike activity and high-frequency fluctuations in membrane potential are closely correlated and that both are more tightly tuned for stimulus orientation than the mean membrane potential. These findings suggest that under high-input conditions the spike-generating mechanism adaptively enhances the sensitivity to synchronous inputs while simultaneously decreasing the sensitivity to temporally uncorrelated inputs.
Summary | Full Text | PDF (232 kb) - Real-Time Kinetic Modeling of Voltage-Gated Ion Channels Usi...Real-Time Kinetic Modeling of Voltage-Gated Ion Channels Using Dynamic Clamp
Biophysical Journal, Volume 95, Issue 1, 1 July 2008, Pages 66-87
Lorin S. Milescu, Tadashi Yamanishi, Krzysztof Ptak, Murtaza Z. Mogri and Jeffrey C. Smith
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Abstract | Full Text | PDF (3005 kb) - Tonic and Phasic Receptor Neurons in the Vertebrate Olfactor...Tonic and Phasic Receptor Neurons in the Vertebrate Olfactory Epithelium
Biophysical Journal, Volume 84, Issue 6, 1 June 2003, Pages 4167-4181
Rodolfo Madrid, Magdalena Sanhueza, Osvaldo Alvarez and Juan Bacigalupo
AbstractOlfactory receptor neurons (ORNs) respond to odorants with characteristic patterns of action potentials that are relevant for odor coding. Prolonged odorant exposures revealed three populations of dissociated toad ORNs, which were mimicked by depolarizing currents: tonic (TN, displaying sustained firing, 49% of 102 cells), phasic (PN, exhibiting brief action potential trains, 36%) and intermediate neurons (IN, generating trains longer than PN, 15%). We studied the biophysical properties underlying the differences between TNs and PNs, the most extreme cases among ORNs. TNs and PNs possessed similar membrane capacitances (∼4pF), but they differed in resting potential (−82 versus −64mV), input resistance (4.2 versus 2.9 GΩ) and unspecific current, (TNs: 0<≤1 pA/pF; and PNs: >1 pA/pF). Firing behavior did not correlate with differences in voltage-gated conductances. We developed a mathematical model that accurately simulates tonic and phasic patterns. Whole cell recordings from rat ORNs in fragments (∼4mm) of olfactory epithelium showed that such a tissue normally contains tonic and phasic receptor neurons, suggesting that this feature is common across a wide range of vertebrates. Our findings show that the individual passive electrical properties can govern the firing patterns of ORNs.
Abstract | Full Text | PDF (292 kb) - …more
Copyright © 1972 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 12, Issue 9, 1145-1158, 1 September 1972
doi:10.1016/S0006-3495(72)86151-4
Articles
Hodgkin-Huxley Axon
B.I. Shapiro and F.K. Lenherr
Abstract
Repetitive response patterns resembling those of tonic receptors were obtained by increasing the potassium system time constant in the Hodgkin-Huxley (H-H) equations. The increase in time constant varied with membrane potential. Calculated spike frequencies varied linearly with the magnitude of the constant current stimulus; in addition, minimum frequencies were greatly reduced, and the frequency range increased. Modification of the maximum ionic conductances, membrane capacitance, and rate constant voltage dependence was found to vary the minimum frequency, current at that frequency, slope, and over-all modulation of the modified responses.
