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Brain networks of spatial awareness: evidence from diffusion tensor imaging tractography
  1. M Urbanski1,2,
  2. M Thiebaut de Schotten1,2,
  3. S Rodrigo3,
  4. M Catani4,
  5. C Oppenheim3,
  6. E Touzé5,
  7. S Chokron6,
  8. J-F Méder3,
  9. R Lévy1,2,7,
  10. B Dubois1,2,7,
  11. P Bartolomeo1,2,7
  1. 1
    INSERM-UPMC UMR S 610, Hôpital de la Salpêtrière, Paris, France
  2. 2
    IFR70, Hôpital de la Salpêtrière, Paris, France
  3. 3
    Department of Neuroradiology, Hôpital Sainte-Anne, Paris, France
  4. 4
    Section of Brain Maturation and Centre for Neuroimaging Science, Institute of Psychiatry, King’s College London, UK
  5. 5
    Department of Neurology, Hôpital Sainte-Anne, Paris, France
  6. 6
    ERT TREAT VISION, CNRS UMR 5105 Paris and Grenoble, France
  7. 7
    Department of Neurology, AP-HP, IFR 70, Hôpital de la Salpêtrière, Paris, France
  1. Dr M Urbanski, INSERM U610, GH Pitié Salpêtrière, 47 boulevard de l’Hôpital, 75013 Paris, France; marika.urbanski{at}gmail.com

Abstract

Left unilateral neglect, a dramatic condition which impairs awareness of left-sided events, has been classically reported after right hemisphere cortical lesions involving the inferior parietal region. More recently, the involvement of long range white matter tracts has been highlighted, consistent with the idea that awareness of events occurring in space depends on the coordinated activity of anatomically distributed brain regions. Damage to the superior longitudinal fasciculus (SLF), linking parietal to frontal cortical regions, or to the inferior longitudinal fasciculus (ILF), connecting occipital and temporal lobes, has been described in neglect patients. In this study, four right-handed patients with right hemisphere strokes underwent a high definition anatomical MRI with diffusion tensor imaging (DTI) sequences and a pencil and paper neglect battery of tests. We used DTI tractography to visualise the SLF, ILF and the inferior fronto-occipital fasciculus (IFOF), a pathway running the depth of the temporal lobe, not hitherto associated with neglect. Two patients with cortical involvement of the inferior parietal and superior temporal regions, but intact and symmetrical fasciculi, showed no signs of neglect. The other two patients with signs of left neglect had superficial damage to the inferior parietal cortex and white matter damage involving the IFOF. These findings suggest that superficial damage to the inferior parietal cortex per se may not be sufficient to produce visual neglect. In some cases, a lesion to the direct connections between ventral occipital and frontal regions (ie, IFOF) may contribute to the manifestation of neglect by impairing the top down modulation of visual areas from the frontal cortex.

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Footnotes

  • Competing interests: None.

  • Ethics approval: The study was approved by the ethics committee of the Hôtel-Dieu Hospital, Paris, France.

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