title: Psychometrically matched tasks evaluating differential fMRI activation during form and motion processing.
abstract: OBJECTIVE
  Deficits in visual perception and working memory are commonly observed in neuropsychiatric disorders and have been investigated using functional MRI (fMRI). However, interpretation of differences in brain activation may be confounded with differences in task performance between groups. Differences in task difficulty across conditions may also pose interpretative issues in studies of visual processing in healthy subjects.
  
  
  METHODS
  To address these concerns, the present study characterized brain activation in tasks that were psychometrically matched for difficulty; fMRI was used to assess brain activation in 10 healthy subjects during discrimination and working memory judgments for static and moving stimuli. For all task conditions, performance accuracy was matched at 70.7%.
  
  
  RESULTS
  Areas associated with V2 and V5 in the dorsal stream were activated during motion processing tasks and V4 in the ventral stream were activated during form processing tasks. Frontoparietal areas associated with working memory were also statistically significant during the working memory tasks.
  
  
  CONCLUSIONS
  Application of psychophysical methods to equate task demands provides a practical method to equate performance levels across conditions in fMRI studies and to compare healthy and cognitively impaired groups at comparable levels of effort. These psychometrically matched tasks can be applied to patients with a variety of cognitive disorders to investigate dysfunction of multiple a priori defined brain regions. Measuring the changes in typical activation patterns in patients with these diseases can be useful for monitoring disease progression, evaluating new drug treatments, and possibly for developing methods for early diagnosis.
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA. ansnyder@purdue.edu
authors.forename: Andrea N
authors.initials: AN
authors.lastname: Snyder
authors.forename: Marcie A
authors.initials: MA
authors.lastname: Bockbrader
authors.forename: Angela M
authors.initials: AM
authors.lastname: Hoffa
authors.forename: Mario A
authors.initials: MA
authors.lastname: Dzemidzic
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Talavage
authors.forename: Donald
authors.initials: D
authors.lastname: Wong
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Lowe
authors.forename: Brian F
authors.initials: BF
authors.lastname: O'Donnell
authors.forename: Anantha
authors.initials: A
authors.lastname: Shekhar
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology*; D011594:Psychometrics; D012016:Reference Values; D055815:Young Adult