title: Cognitive functions in multiple sclerosis: impact of gray matter integrity.
abstract: OBJECTIVE
  Our aim was to investigate the impact of gray matter (GM) integrity on cognitive performance in multiple sclerosis (MS), and its relationship with white matter (WM) integrity and presence of lesions.
  
  
  METHODS
  Sixty-seven patients with MS and 26 healthy controls underwent voxel-based analysis of diffusion tensor images (DTI) in GM and tract-based spatial statistics (TBSS) from WM to identify the regional correlations between cognitive functions and integrity. Lesion probability mapping (LPM) was generated for correlation analysis with cognition. Multiple linear regression analyses were used to identify the imaging measures associated with cognitive scores.
  
  
  RESULTS
  Compared with controls, patients showed abnormal DTI indices in several GM regions and in most WM tracts. Impairment in DTI indices in specific GM regions was associated with worse performance of distinct cognitive functions. Those regions showed anatomical correspondence with cognitively relevant tracts in TBSS and LPM. The combination of regional GM and WM DTI and lesion volume accounted for 36-51% of the variance of memory and attention scores. Regional GM DTI explained less than 5% of that variance.
  
  
  CONCLUSIONS
  GM and WM integrity of specific networks influences cognitive performance in MS. However, GM damage assessed by DTI only adds a small increment to the explained variance by WM in predicting cognitive functioning.
authors.affiliation: Center for Neuroimmunology, Service of Neurology, Hospital Clinic and Institut d'Investigacions Biomèdiques August Pi I Sunyer (IDIBAPS), Universitat de Barcelona, Barcelona, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: Llufriu
authors.forename: Eloy
authors.initials: E
authors.lastname: Martinez-Heras
authors.forename: Juan
authors.initials: J
authors.lastname: Fortea
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Blanco
authors.forename: Joan
authors.initials: J
authors.lastname: Berenguer
authors.forename: Iñigo
authors.initials: I
authors.lastname: Gabilondo
authors.forename: Naroa
authors.initials: N
authors.lastname: Ibarretxe-Bilbao
authors.forename: Carles
authors.initials: C
authors.lastname: Falcon
authors.forename: Maria
authors.initials: M
authors.lastname: Sepulveda
authors.forename: Nuria
authors.initials: N
authors.lastname: Sola-Valls
authors.forename: Nuria
authors.initials: N
authors.lastname: Bargallo
authors.forename: Francesc
authors.initials: F
authors.lastname: Graus
authors.forename: Pablo
authors.initials: P
authors.lastname: Villoslada
authors.forename: Albert
authors.initials: A
authors.lastname: Saiz
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology*; D003072:Cognition Disorders / Q000209:etiology* / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000150:complications* / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D009483:Neuropsychological Tests
keywords: MRI; Multiple sclerosis; cognitive function; diffusion tensor imaging; tract-based spatial statistics; voxel-based analysis