Discontinuity of cortical gradients reflects sensory impairment

Noam Saadon-Grosman, Zohar Tal, Eyal Itshayek, Amir Amedi, Shahar Arzy*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Topographic maps and their continuity constitute a fundamental principle of brain organization. In the somatosensory system, wholebody sensory impairment may be reflected either in cortical signal reduction or disorganization of the somatotopic map, such as disturbed continuity. Here we investigated the role of continuity in pathological states. We studied whole-body cortical representations in response to continuous sensory stimulation under functional MRI (fMRI) in two unique patient populations-patients with cervical sensory Brown-Séquard syndrome (injury to one side of the spinal cord) and patients before and after surgical repair of cervical disk protrusion-enabling us to compare whole-body representations in the same study subjects. We quantified the spatial gradient of cortical activation and evaluated the divergence from a continuous pattern. Gradient continuity was found to be disturbed at the primary somatosensory cortex (S1) and the supplementary motor area (SMA), in both patient populations: contralateral to the disturbed body side in the Brown-Séquard group and before repair in the surgical group, which was further improved after intervention. Results corresponding to the nondisturbed body side and after surgical repair were comparable with control subjects. No difference was found in the fMRI signal power between the different conditions in the two groups, as well as with respect to control subjects. These results suggest that decreased sensation in our patients is related to gradient discontinuity rather than signal reduction. Gradient continuity may be crucial for somatotopic and other topographical organization, and its disruption may characterize pathological processing.

Original languageAmerican English
Pages (from-to)16024-16029
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume112
Issue number52
DOIs
StatePublished - 29 Dec 2015

Bibliographical note

Funding Information:
We thank our patients for their kind agreement to participate in the study; Prof. M. Gomori, Mrs. S. Fisch, Mrs. O. Shamir, Dr. A. Bick, O. Asulin, and the staff of the MRI unit of Hadassah Hebrew University Medical Center for help in patients'' management; Prof. M. Timme, M. Peer, Dr. U. Hertz, and S. Aboud for help in data analysis; and Dr. L. Grosman, Prof. T. Ben-Hur, D. Arzi, and R. Shilo for thoughtful discussions and support. This study was supported by a Marie Curie Intra-European Fellowship within the framework of European Union-Seventh Framework Programme for Research and Technological Development PIEFGA-2012-328124 and by the Templeton Foundation within the framework of the Immortality Project, led by Prof. John M. Fischer (S.A.); the Levzion Program (Z.T.); European Research Council Grant 310809; and The James S. McDonnell Foundation Award 220020284 (to A.A.).

Keywords

  • FMRI
  • Plasticity
  • Somatotopy
  • Topographic maps
  • Whole-body representation

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