Rheobase

Fig. 1 – Rheobase and chronaxie are points defined on the strength-duration curve for stimulus of an excitable tissue.

Rheobase is a measure of membrane potential excitability. In neuroscience, rheobase is the minimal current amplitude of infinite duration that results in the depolarization threshold of the cell membranes being reached, such as an action potential or the contraction of a muscle.[1] In Greek, the root rhe translates to "current or flow", and basi means "bottom or foundation": thus the rheobase is the minimum current that will produce an action potential or muscle contraction.

Rheobase can be best understood in the context of the strength-duration relationship (Fig. 1).[2] The ease with which a membrane can be stimulated depends on two variables: the strength of the stimulus, and the duration for which the stimulus is applied.[3] These variables are inversely related: as the strength of the applied current increases, the time required to stimulate the membrane decreases (and vice versa) to maintain a constant effect.[3] Mathematically, rheobase is equivalent to half the current that needs to be applied for the duration of chronaxie, which is a strength-duration time constant that corresponds to the duration of time that elicits a response when the nerve is stimulated at twice rheobasic strength.[3]

The strength-duration curve was first discovered by G. Weiss in 1901, but it was not until 1909 that Louis Lapicque coined the term rheobase.[4] Many studies are being conducted in relation to rheobase values and the dynamic changes throughout maturation and between different nerve fibers.[5] In the past strength-duration curves and rheobase determinations were used to assess nerve injury; today, they play a role in clinical identification of many neurological pathologies, including diabetic neuropathy, CIDP, Machado–Joseph disease,[6] and ALS.[7]

  1. ^ Ashley, et al. "Determination of the Chronaxie and Rheobase of Denervated Limb Muscles in Conscious Rabbits". Artificial Organs, Volume 29 Issue 3 Page 212 - March 2005
  2. ^ Fleshman et al. "Rheobase, input resistance, and motor-unit type in medial gastrocnemius motoneurons in the cat." Journal of Neurophysiology, 1981.
  3. ^ a b c Boinagrov, D., et al. (2010). "Strength-duration relationship for extracellular neural stimulation: Numerical and analytical models". Journal of Neurophysiology, 194(2010), 2236–2248.
  4. ^ Cite error: The named reference Geddes, 2004 was invoked but never defined (see the help page).
  5. ^ Carrascal, et al. (2005). "Changes during postnatal development in physiological and anatomical characteristics of rat motoneurons studied in vitro". Brain Research Reviews, 49(2005), 377–387.
  6. ^ Nodera, H., & Kaji, R. (2006). "Nerve excitability testing in its clinical application to neuromuscular diseases". Clinical Neurophysiology, 117(2006), 1902–1916.
  7. ^ Mogyoros, I., et al. (1998). "Strength-duration properties of sensory and motor axons in amyotrophic lateral sclerosis". Brain, 121(1998), 851–859.