Spontaneous firing increases dramatically below a critical diameter in rat (triangles) and squid (circles) axons.

FAISAL/ELSEVIER

Noise means an axon can be only so small before it fails, say Aldo Faisal, Simon Laughlin (University of Cambridge, UK), and John White (Boston University, Boston, MA).

Axons are inherently noisy due to the spontaneous openings and closings of ion channels that cause membrane potential fluctuations. When the noise becomes too great, a spontaneous action potential ensues, which can disrupt communication between axons. As the rate of this spontaneous firing increases exponentially as axon diameter decreases, Faisal wondered whether channel noise limits axon size.

To test this question, the team developed a mathematical model that tracks axon dynamics when single ion channels “behave badly,” or open and close at the maximum threshold observed experimentally. Using data from well-studied biological systems, such as specialized cortical rodent and squid axons,...

The Rockefeller University Press
2005
The Rockefeller University Press
2005
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