White matter (dis)connections and gray matter (dys)functions in visual neglect: Gaining insights into the brain networks of spatial awareness
Cortex. 2008-09-01; 44(8): 983-995
DOI: 10.1016/j.cortex.2008.03.006
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1. Cortex. 2008 Sep;44(8):983-95. doi: 10.1016/j.cortex.2008.03.006. Epub 2008 May
23.
White matter (dis)connections and gray matter (dys)functions in visual neglect:
gaining insights into the brain networks of spatial awareness.
Doricchi F(1), Thiebaut de Schotten M, Tomaiuolo F, Bartolomeo P.
Author information:
(1)Dipartimento di Psicologia 39, Università degli Studi di Roma La Sapienza,
Rome, Italy.
Seminal case reports collected during the middle part of the XX century,
designated the parietal lobe as the principal area of damage in patients
suffering from contralesional spatial neglect (Brain WC. Visual disorientation
with special reference to lesions of the right cerebral hemisphere. Brain
1941;64:224-72; Paterson A, Zangwill O. Disorders of visual space perception
associated with lesions of the right cerebral hemisphere. Brain 1944;67:331-58;
McFie J, Piercy MF, Zangwill O. Visual spatial agnosia associated with lesions of
the right hemisphere. Brain 1950;73:167-90). Based on this evidence, textbooks of
neurology have traditionally referred to neglect as a « parietal sign ». This view
found complete accomplishment in the 1986 group study by Vallar and Perani, who
confirmed that the inferior parietal lobe was the area most frequently involved
in neglect patients with lesions confined to the cerebral cortex and lesions
involving subcortical gray matter nuclei. In the same study, it was found that
lesions limited to subcortical white matter were rarely associated with neglect.
Here, we reconsider recent accumulating evidence, gathered from investigations in
animals and human patients, supporting the partially different view that damage
involvement of long-range white matter bundles connecting the parietal to the
frontal lobe, importantly influence the occurrence and severity of spatial
neglect. These findings do not dispute the role of the parietal and frontal
cortex in spatial attention and space-related behaviour, but call for a
reappraisal of the respective roles of disruption of white matter connections and
damage of gray matter cortical modules in the pathophysiology of neglect.
Disentangling the connectional and modular anatomical correlates of neglect may
be crucial to better understand the pathophysiology of this syndrome, to explain
the manifold clinical dissociations often encountered in clinical practice and to
increase the impact of behavioural and pharmacological interventions. In this
review, we focus on the role of within-hemisphere white-matter disconnection. The
role of interhemispheric disconnection, perhaps the oldest connectionist theory
of neglect (Geschwind N. Disconnexion syndromes in animals and man – part II.
Brain 1965;88:585-644), was extensively treated elsewhere (Bartolomeo P, Thiebaut
de Schotten M, Doricchi F. Left unilateral neglect as a disconnection syndrome,
Cerebral Cortex 2007;45:3127-48). We first summarise the structure of long-range
white matter connections within the cerebral hemispheres and sketch a brief
historical review of the original findings suggesting the role of
intrahemispheric disconnection to neglect. We then revisit some of the current
functional interpretation of the neglect syndrome in the light of
disconnectionist approach and review evidences favouring or disfavouring a purely
disconnectionist interpretation of the syndrome. Finally, we address the issue of
diagnostic criteria to be used in future anatomo-clinical studies aiming at
investigating the role of white matter and gray matter dysfunctions in spatial
neglect.
DOI: 10.1016/j.cortex.2008.03.006
PMID: 18603235 [Indexed for MEDLINE]