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New insights into the anatomo-functional connectivity of
the semantic system: a study using cortico-subcortical electrostimulations
Duffau H, Gatignol P, Mandonnet E, Peruzzi P, Tzourio-Mazoyer N, Capelle
L
Department of Neurosurgery, U 678, Hopital Salpetriere, 47-83 Bd de
l'Hopital, 75651 Paris, Cedex 13, France. hugues.duffau@psl.ap-hop-paris.fr
Despite a better understanding of the organization of the cortical network
underlying the semantic system, very few data are currently available
regarding its anatomo-functional connectivity.
Here, we report on a series
of 17 patients operated on under local anaesthesia for a cerebral low-grade
glioma located within the dominant hemisphere.
Prior to and during
resection, intraoperative electrical stimulation was used to map
sensorimotor and language structures so that permanent neurological deficits
could be avoided.
In a number of cases, cortical and subcortical stimulation
caused semantic paraphasias.
Using postoperative MRI, we correlated these
functional findings with the anatomical locations of the sites where
semantic errors were elicited by stimulation, especially at the subcortical
level, with the aim of studying the connectivity underlying the semantic
system.
In temporal gliomas, cortical sites involved in semantic processing
were found around the posterior part of the superior temporal sulcus, with
subcortical pathways reproducibly located under the depth of this sulcus.
In
insular gliomas, although stimulation elicited no semantic disturbances at
the cortical level, such semantic paraphasias were generated at the level of
the anterior floor of the external capsule.
In frontal tumours, cortical
regions implicated in semantics were detected in the lateral orbitofrontal
region and dorsolateral prefrontal cortex, with subcortical fibres located
under the inferior frontal sulcus.
All these eloquent structures were
systematically preserved, thereby avoiding permanent postoperative deficits.
Our results provide arguments in favour of the existence of a main ventral
subcortical pathway underlying the semantic system, within the dominant
hemisphere, joining the two essential cortical epicentres of this network:
the posterior and superior temporal areas, and the orbitofrontal and
dorsolateral prefontal regions.
Such a ventral stream might anatomically
partly correspond to the inferior fronto-occipital fasciculus.
PMID: 15705610 [PubMed - indexed for MEDLINE]
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