title: Neural mechanisms underlying the facilitation of naming in aphasia using a semantic task: an fMRI study.
abstract: BACKGROUND
  Previous attempts to investigate the effects of semantic tasks on picture naming in both healthy controls and people with aphasia have typically been confounded by inclusion of the phonological word form of the target item. As a result, it is difficult to isolate any facilitatory effects of a semantically-focused task to either lexical-semantic or phonological processing. This functional magnetic resonance imaging (fMRI) study examined the neurological mechanisms underlying short-term (within minutes) and long-term (within days) facilitation of naming from a semantic task that did not include the phonological word form, in both participants with aphasia and age-matched controls.
  
  
  RESULTS
  Behavioral results showed that a semantic task that did not include the phonological word form can successfully facilitate subsequent picture naming in both healthy controls and individuals with aphasia. The whole brain neuroimaging results for control participants identified a repetition enhancement effect in the short-term, with modulation of activity found in regions that have not traditionally been associated with semantic processing, such as the right lingual gyrus (extending to the precuneus) and the left inferior occipital gyrus (extending to the fusiform gyrus). In contrast, the participants with aphasia showed significant differences in activation over both the short- and the long-term for facilitated items, predominantly within either left hemisphere regions linked to semantic processing or their right hemisphere homologues.
  
  
  CONCLUSIONS
  For control participants in this study, the short-lived facilitation effects of a prior semantic task that did not include the phonological word form were primarily driven by object priming and episodic memory mechanisms. However, facilitation effects appeared to engage a predominantly semantic network in participants with aphasia over both the short- and the long-term. The findings of the present study also suggest that right hemisphere involvement may be supportive rather than maladaptive, and that a large distributed perisylvian network in both cerebral hemispheres supports the facilitation of naming in individuals with aphasia.
authors.affiliation: University of Queensland, Language Neuroscience Laboratory, Centre for Clinical Research, Brisbane, Queensland, Australia. shiree.heath@uq.edu.au
authors.forename: Shiree
authors.initials: S
authors.lastname: Heath
authors.forename: Katie L
authors.initials: KL
authors.lastname: McMahon
authors.forename: Lyndsey
authors.initials: L
authors.lastname: Nickels
authors.forename: Anthony
authors.initials: A
authors.lastname: Angwin
authors.forename: Anna D
authors.initials: AD
authors.lastname: Macdonald
authors.forename: Sophia
authors.initials: S
authors.lastname: van Hees
authors.forename: Kori
authors.initials: K
authors.lastname: Johnson
authors.forename: Eril
authors.initials: E
authors.lastname: McKinnon
authors.forename: David A
authors.initials: DA
authors.lastname: Copland
mesh_terms: D000328:Adult; D000368:Aged; D001037:Aphasia / Q000473:pathology* / Q000503:physiopathology; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009275:Names; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D012660:Semantics; D018709:Statistics, Nonparametric
chemical_list: D010100:Oxygen