Squid axon membrane response to white noise stimulation.
The current from a white noise generator was applied as a stimulus to a space-clamped squid axon in double sucrose gap. The membrane current and the voltage response of the membrane were then amplified, recorded on magnetic tape, and the stimulus was cross-correlated with the response. With subthreshold stimuli, a cross-correlation function resembling that obtained from a resonant parallel circuit is obtained. As the intensity of the input noise is increased, the cross-correlation function resembles that obtained from a less damped oscillatory circuit. When the noise intensity is further increased so that an appreciable frequency of action potentials is observed, an additional component appears in the experimental cross-correlogram. The subthreshold cross-correlogram is analyzed theoretically in terms of the linearized Hodgkin-Huxley equations. The subthreshold axon approximates a parallel resonant circuit. The circuit parameters are temperature dependent, with resonant frequency varying from approximately 100 Hz at 10 degrees C to approximately 250 Hz at 20 degrees C. The Q(10) of the resonant frequency is equal to 1.9. These values are in agreement with values found previously for subthreshold oscillations following a single action potential.
D000161:Acoustic Stimulation; D000200:Action Potentials; D000818:Animals; D001369:Axons / Q000502:physiology*; D003201:Computers; D049832:Decapodiformes; D008433:Mathematics; D008564:Membrane Potentials; D008566:Membranes / Q000502:physiology; D009622:Noise; D009991:Oscillometry; D013057:Spectrum Analysis; D013395:Sucrose; D013696:Temperature; D013997:Time Factors
D013395:Sucrose