Monophasic and biphasic stimulation evoke different responses

Edelle C. Field-Fote, Brent Anderson, Valma J. Robertson, Neil I. Spielholz

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


In 31 subjects, psychophysiological sensory perception threshold and the waveform of orthodromic sensory nerve action potentials (SNAPs) produced by constant-current 100-μs monophasic negative pulses were compared to those produced by biphasic (negative-positive) symmetrical pulses (100-μs per phase). In addition, the effects of 200-μs monophasic negative pulses were studied. Graded stimuli were delivered to the index finger, and SNAPs were recorded over the median nerve at the wrist. Perception threshold was significantly different among the three conditions. Furthermore, in 26 subjects, at the lower intensities at which SNAPs first appeared, the evoked potential waveform had two small negative phases with biphasic stimuli, but a single negative phase in response to monophasic pulses. At higher stimulus intensities, all SNAPs had a single large negative phase regardless of the stimulus. These perception and waveform findings suggest that, contrary to historical belief, the trailing positive phase of a biphasic pulse has a stimulating effect at low stimulus intensities.

Original languageEnglish (US)
Pages (from-to)239-241
Number of pages3
JournalMuscle and Nerve
Issue number2
StatePublished - Aug 1 2003
Externally publishedYes


  • Electrical stimulation
  • Sensory nerve action potential
  • Sensory threshold
  • Stimulus waveform

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)


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