Hemispheric asymmetry in global/local processing: Effects of stimulus position and spatial frequency

Shihui Han, Janelle A. Weaver, Scott O. Murray, Xiaojian Kang, E. William Yund, David L Woods

Research output: Contribution to journalArticle

111 Scopus citations

Abstract

We examined the neural mechanisms of functional asymmetry between hemispheres in the processing of global and local information of hierarchical stimuli by measuring hemodynamic responses with functional magnetic resonance imaging (fMRI). In a selective attention task, subjects responded to targets at the global or local level of compound letters that were (1) broadband in spatial-frequency spectrum and presented at fixation; (2) broadband and presented randomly to the left or the right of fixation; or (3) contrast balanced (CB) to remove low spatial frequencies (SFs) and presented at fixation. Central broadband stimuli induced stronger activation in the right middle occipital cortex under global relative to local attention conditions but in the left inferior occipital cortex, stronger activation was induced under local relative to global attention conditions. The asymmetry over the occipital cortex was weakened by unilateral presentation and by contrast balancing. The results indicate that the lateralization of global and local processing is modulated by the position and SF spectrum of the compound stimuli. The global attention also produced stronger activation over the medial occipital cortex relative to the local attention under all the stimulus conditions. The nature of these effects is discussed.

Original languageEnglish (US)
Pages (from-to)1290-1299
Number of pages10
JournalNeuroImage
Volume17
Issue number3
DOIs
StatePublished - 2002

Keywords

  • Compound stimulus
  • Contrast balancing
  • fMRI
  • Global/local processing
  • Hemispheric asymmetry
  • Occipital cortex
  • Spatial frequency

ASJC Scopus subject areas

  • Cognitive Neuroscience
  • Neurology

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