the neural correlates of auditory and visuospatial span in logopenic progressive aphasia and alzheimers disease introduction logopenic progressive aphasia lvppa is a form of primary progressive aphasia and is predominantly associated with alzheimers disease ad pathology the neuropsychological profiles of lvppa and typical clinical ad are however distinct in particular these two syndromes differ on attention span measures where auditory attention span is more impaired in lvppa than in ad and visuospatial span appears more impaired in ad than in lvppa the neural basis of these span profiles however remains unclearmethod sixteen lvppa and 21 ad matched patients and 15 educationmatched healthy controls were recruited all participants were assessed by a neurologist and completed a neuropsychological assessment that included the wechsler memory scaleiii digit and spatial span tasks and underwent a highresolution structural brain mri to conduct cortical thickness analysesresults patient groups were impaired on all span tasks compared to controls in addition performance on digit span forward dsf was significantly lower in the lvppa than the ad group while spatial span forward ssf was significantly lower in the ad than the lvppa group no differences were found between patient groups on the digit or spatial span backward tasks neuroimaging analyses revealed that reduced dsf performance correlated to thinning of the left superior temporal gyrus in the lvppa group whereas reduced ssf performance was related to bilateral precentral sulcus and parietooccipital thinning in the ad group analyses of the backward span tasks revealed that reduced spatial span backward ssb performance in the lvppa group related to cortical thinning of the left superior parietal lobuleconclusions this study demonstrates that while lvppa and ad commonly share the same underlying neuropathology their span profiles are distinct and are mediated by divergent patterns of cortical degeneration