Field potentials evoked in rat primary somatosensory cortex (SI) by impulses in cutaneous A beta- and C-fibres

Brain Res. 1986 Nov 5;397(1):86-92. doi: 10.1016/0006-8993(86)91371-5.


A projection of cutaneous C-afferent fibres to the contralateral primary somatosensory cortex (SI) was examined in the halothane-anaesthetized rat. Field potentials evoked by electrical stimulation of the right sural nerve were recorded at the surface of an intracortically within the left SI cortex. A late surface positive potential (latency 110-190 ms, mean 136 ms) was evoked by sural stimulation at a strength that activated A- and C-fibres. A selective anodal block of impulse conduction in A-fibres proximal to the stimulating electrodes showed that impulses in C-fibres generate the late potential also in the absence of a preceding A-fibre input. Stimulation of the sural nerve at two sites caused a shift in latency of the late potential corresponding to a conduction velocity of the primary afferent fibres of less than 1.0 m/s. The distribution of the C-fibre-evoked potential in SI was similar to that of the A beta-fibre evoked 'primary' potential suggesting that the investigated projection of cutaneous C-fibres to SI has a somatotopic organization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials
  • Afferent Pathways / physiology
  • Animals
  • Evoked Potentials, Somatosensory
  • Male
  • Nerve Fibers / physiology*
  • Nerve Fibers, Myelinated / physiology*
  • Pain / physiopathology*
  • Rats
  • Rats, Inbred Strains
  • Skin / innervation*
  • Somatosensory Cortex / physiology*
  • Sural Nerve / physiology