Brain Advance Access originally published online on September 28, 2006
Brain 2007 130(2):431-441; doi:10.1093/brain/awl265
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Neural bases of personal and extrapersonal neglect in humans
1 Department of Clinical Sciences and Bioimaging, University Gabriele d'Annunzio and ITAB-Institute for Advanced Biomedical Technologies Fondazione Gabriele d'Annunzio, Chieti, Italy 2 Neuroimaging Laboratory, I.R.C.C.S. Fondazione Santa Lucia Rome 3 Laboratory of Neuropsychology, I.R.C.C.S. Fondazione Santa Lucia Rome, Italy 4 Department of Psychology, University of Rome ‘La Sapienza’, Rome, Italy 5 Ars Radiologica Lecce, Italy
Correspondence to: Giorgia Committeri, Department of Clinical Sciences and Bioimaging, University Gabriele d'Annunzio, via dei Vestini 29, 66100 Chieti, Italy E-mail: gcommitteri{at}unich.it
Human awareness of left space may be disrupted by cerebral lesions to the right hemisphere (hemispatial neglect). Current knowledge on the anatomical bases of this complex syndrome is based on the results of group studies that investigated primarily the best known aspect of the syndrome, which is visual neglect for near extrapersonal (or peripersonal) space. However, another component–neglect for personal space–is more often associated with, than double-dissociated from, extrapersonal neglect, especially, in chronic patients. The present investigation aimed at exploring the anatomical substrate of both extrapersonal and personal neglect by using different advanced methodological approaches to lesion–function correlation. Fifty-two right ischaemic patients were submitted to neuropsychological assessment and in-depth MRI evaluation. The borders of each patient's lesion were delimited onto its own high-resolution anatomical image and then submitted to an automated spatial normalization algorithm. Besides conventional lesion density plots and subtraction analysis, region-based statistical analyses were performed on percentage values of the lesioned tissue also using a new parcellation of the white matter (WM). Data were finally submitted to voxelwise statistical analysis using a recently proposed method (voxel-based lesion–symptom mapping). Results converged in showing that awareness of extrapersonal space is based on the integrity of a circuit of right frontal (ventral premotor cortex and middle frontal gyrus) and superior temporal regions, whereas awareness of personal space is rooted in right inferior parietal regions (supramarginal gyrus, post-central gyrus and especially the WM medial to them). Common but less crucial regions for both neglect sub-types were located in the temporo-peri-Sylvian cortex. We suggest that extrapersonal space awareness critically involves a ventral circuit recently described for the exogenous allocation and reorienting of attention in space. Disruption of personal space awareness, instead, seems to be due to a functional disconnection between regions important for coding proprioceptive and somatosensory inputs, and regions coding more abstract egocentric representations of the body in space. In conclusion, present data strongly support a segregation of personal and extrapersonal spatial awareness in humans, both from a functional and an anatomical point of view.
Key Words: hemispatial neglect; personal; extrapersonal; frontal; parietal
Abbreviations: CR, corona radiata; FEF, frontal eye field; IPL, inferior parietal lobule; MFG, middle frontal gyrus; SMG, supramarginal gyrus; VLSM, voxel-based lesion–symptom mapping; WM, white matter
Received February 21, 2006. Revised August 7, 2006. Accepted August 8, 2006.
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