Brain networks of spatial awareness: Evidence from diffusion tensor imaging tractography
Journal of Neurology, Neurosurgery & Psychiatry. 2008-05-01; 79(5): 598-601
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1. J Neurol Neurosurg Psychiatry. 2008 May;79(5):598-601. Epub 2007 Nov 8.
Brain networks of spatial awareness: evidence from diffusion tensor imaging
Urbanski M(1), Thiebaut de Schotten M, Rodrigo S, Catani M, Oppenheim C, Touzé E,
Chokron S, Méder JF, Lévy R, Dubois B, Bartolomeo P.
(1)INSERM-UPMC UMR S 610, Hôpital de la Salpêtrière, Paris, France.
J Neurol Neurosurg Psychiatry. 2008 May;79(5):490-1.
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.
PMID: 17991702 [Indexed for MEDLINE]