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Spinal sensorimotor transformation: Relation between cutaneous somatotopy and a reflex network

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Author

Summary, in English

The projection of primary afferents onto spinal interneurons constitutes the first step in sensorimotor transformations performed by spinal reflex systems. Despite extensive studies on spinal somatotopy, uncertainties remain concerning the extent and significance of representational overlap and relation to spinal reflex circuits. To address these issues, the cutaneous projection from the hindpaw and its relation to the topography of lamina V neurons encoding withdrawal reflex strength ("reflex encoders") was studied in rats. Thin and coarse primary afferent terminations in laminas II and III-IV, respectively, were mapped by wheat germ agglutinin-horseradish peroxidase and choleragenoid tracing. The functional weights of these projections were characterized by mapping nociceptive and tactile field potentials and compared with the topography of reflex encoders. Both anatomical and physiological data indicate that thin and coarse skin afferent input is spatially congruent in the horizontal plane. The representation of the hindpaw in the spinal cord was found to be intricate, with a high degree of convergence between the projections from different skin sites. "Somatotopic disruptions" such as the representation of central pads medial to that of the digits were common. The weight distribution of the cutaneous convergence patterns in laminas III-IV was similar to that of lamina V reflex encoders. This suggests that the cutaneous convergence and features such as somatotopic disruptions have specific relations to the sensorimotor transformations performed by reflex interneurons in the deep dorsal horn. Hence, the spinal somatotopic map may be better understood in light of the topography of such reflex systems.

Publishing year

2002

Language

English

Pages

8170-8182

Publication/Series

Journal of Neuroscience

Volume

22

Issue

18

Document type

Journal article

Publisher

Society for Neuroscience

Topic

  • Ophthalmology
  • Neurosciences
  • Radiology, Nuclear Medicine and Medical Imaging

Keywords

  • reflex
  • spinal cord
  • somatosensory
  • receptive field
  • somatotopic
  • sensorimotor
  • primary afferent

Status

Published

Research group

  • Radiology Diagnostics, Malmö
  • Neurophysiology
  • Neuronano Research Center (NRC)

ISBN/ISSN/Other

  • ISSN: 1529-2401