Sensory nerve crush and regeneration and the receptive fields and response properties of neurons in the primary somatosensory cerebral cortex of cats.
Extracellular recordings were made of activity evoked in neurons of the forepaw focus of somatosensory cerebral cortex by electrical stimulation of each paw in control cats and cats that had undergone crush injury of all cutaneous sensory nerves to the contralateral forepaw 31 to 63 days previously. Neurons responding only to stimulation of the contralateral forepaw were classified as sa; neurons responding to stimulation of both forepaws were classified as sb; neurons responding to stimulation of both contralateral paws were classified as sc; and neurons responding to stimulation of at least three paws were classified as m. The ratio sa:sb:sc:m neurons was 46:3:0:0 in control cats and 104:15:3:26 in cats that had undergone nerve crush 1-2 months prior to study. sa neurons from experimental cats had depth distributions similar to those in controls and responded to contralateral forepaw stimulation with more spikes per discharge, longer latency, and higher threshold than sa neurons in control cats. m neurons from experimental cats were distributed deeper in the cortex than sa neurons, and, when compared to experimental sa neurons, they responded with longer latency and poorer frequency-following ability; however, the number of spikes per discharge and threshold were not significantly different. The appearance of wide-field neurons in this tissue may be explained in terms of strengthening of previously sub-threshold inputs to neurons in the somatosensory system. If the neurons in sensory cortex play a requisite role in cutaneous sensations and if changes similar to those reported here occur and persist in human cortex after nerve crush, then "complete" recovery of sensation in such patients may occur against a background of changed cortical neuronal responsiveness.
Brandenberg
G A
GA
Department of Physiology and Biophysics, University of Nebraska Medical Center, Omaha 68105-1065.
Mann
M D
MD
D000200:Action Potentials; D000818:Animals; D002415:Cats; D004056:Differential Threshold; D009409:Nerve Crush; D009416:Nerve Regeneration; D009424:Nervous System Physiological Phenomena; D009474:Neurons / Q000502:physiology*; D011930:Reaction Time; D012016:Reference Values; D012677:Sensation / Q000502:physiology*; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*