title: Effects of task complexity on activation of language areas in a semantic decision fMRI protocol.
abstract: Language tasks used for clinical fMRI studies may be too complex for some patients with cognitive impairments, and "easier" versions are sometimes substituted, though the effects on brain activity of such changes in task complexity are largely unknown. To investigate these differences, we compared two versions of an fMRI language comprehension protocol, with different levels of difficulty, in 24 healthy right-handed adults. The protocol contrasted an auditory word comprehension task (semantic decision) with a nonspeech control task using tone sequences (tone decision). In the "complex" version (CV), the semantic decision task required two complex semantic decisions for each word, and the tone decision task required the participant to count the number of target tones in each sequence. In the "easy" version (EV), the semantic task required only a single easier decision, and the tone task required only detection of the presence or absence of a target tone in each sequence. The protocols were adapted for a Brazilian population. Typical left hemisphere language lateralization was observed in 92% of participants for both CV and EV using the whole-brain lateralization index, and typical language lateralization was also observed for others regions of interest. Task performance was superior on the EV compared to the CV (p=0.014). There were many common areas of activation across the two version; however, the CV produced greater activation in the left superior and middle frontal giri, angular gyrus, and left posterior cingulate gyrus compared to the EV, the majority of which are areas previously identified with language and semantic processing. The EV produced stronger activation only in a small area in the posterior middle temporal gyrus. These results reveal differences between two versions of the protocol and provide evidence that both are useful for language lateralization and worked well for Brazilian population. The complex version produces stronger activation in several nodes of the semantic network and therefore is elected for participants who can perform well these tasks.
authors.affiliation: Department of Neurology, University of Campinas, Campinas, SP, Brazil.
authors.forename: Tátila Martins
authors.initials: TM
authors.lastname: Lopes
authors.affiliation: Department of Neurology, University of Campinas, Campinas, SP, Brazil.
authors.forename: Clarissa Lin
authors.initials: CL
authors.lastname: Yasuda
authors.affiliation: Department of Neurology, University of Campinas, Campinas, SP, Brazil.
authors.forename: Brunno Machado de
authors.initials: BM
authors.lastname: Campos
authors.affiliation: Department of Neurology, University of Campinas, Campinas, SP, Brazil.
authors.forename: Marcio L F
authors.initials: MLF
authors.lastname: Balthazar
authors.affiliation: Department of Neurology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Binder
authors.affiliation: Department of Neurology, University of Campinas, Campinas, SP, Brazil. Electronic address: fcendes@unicamp.br.
authors.forename: Fernando
authors.initials: F
authors.lastname: Cendes
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000502:physiology*; D001931:Brain Mapping; D003657:Decision Making / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007802:Language; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D012660:Semantics; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: Language lateralization; Methodology; Semantic processing; fMRI