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Brain networks of spatial awareness: Evidence from diffusion tensor imaging tractography
  1. Marika Urbanski (marika.urbanski{at}gmail.com)
  1. INSERM Unit 610, France
    1. Michel Thiebaut De Schotten (michel.thiebaut{at}gmail.com)
    1. INSERM Unit 610, France
      1. Sebastian Rodrigo (seb.rodrigo{at}gmail.com)
      1. Sainte-Anne Hospital, France
        1. Marco Catani (marco.catani{at}iop.kcl.ac.uk)
        1. institute of psychiatry King's College of London, United Kingdom
          1. Catherine Oppenheim (c.oppenheim{at}ch-sainte-anne.fr)
          1. Sainte-Anne Hospital, France
            1. Emmanuel Touze (e.touze{at}ch-sainte-anne.fr)
            1. Sainte-Anne Hospital, France
              1. Sylvie Chokron (chokron{at}ext.jussieu.fr)
              1. CNRS UMR 5105, France
                1. Jean-Francois Meder (jf.meder{at}ch-sainte-anne.fr)
                1. Sainte-Anne Hospital, France
                  1. Richard Levy (richard.levy{at}psl.aphp.fr)
                  1. INSERM Unit 610, France
                    1. Bruno Dubois (bruno.dubois{at}psl.aphp.fr)
                    1. INSERM Unit 610, France
                      1. Paolo Bartolomeo (paolo.bartolomeo{at}gmail.com)
                      1. INSERM Unit 610, France

                        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, have been described in neglect patients. In this study four right-handed patients with right-hemisphere strokes were submitted to a high-definition anatomical MRI with diffusion tensor imaging (DTI) sequences and to a paper-and-pencil neglect battery. We used DTI tractography to visualize the SLF, the ILF and the inferior fronto-occipital fasciculus (IFOF), a pathway running in 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 (i.e. IFOF) may contribute to the manifestation of neglect by impairing the top-down modulation of visual areas from frontal cortex.

                        • diffusion MRI
                        • spatial attention
                        • unilateral neglect

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