Understanding neural system dynamics through task modulation and measurement of functional MRI amplitude, latency, and width.

Full Abstract

Estimates of hemodynamic amplitude, delay, and width were combined to investigate system dynamics involved in lexical decision making. Subjects performed a lexical decision task using word and nonword stimuli rotated 0 degrees, 60 degrees, or 120 degrees. Averaged hemodynamic responses to repeated stimulation were fit to a Gamma-variate function convolved with a heavyside function of varying onset and duration to estimate each voxel's activation delay and width. Consistent with prolonged reaction times for the rotated stimuli and nonwords, the motor cortex showed delayed hemodynamic onset for both conditions. Language areas such as the lingual gyrus, middle temporal gyrus, fusiform gyrus, and precuneus all showed delayed hemodynamic onsets to rotated stimuli but not to nonword stimuli. The inferior frontal gyrus showed both increased onset latency for rotated stimuli and a wider hemodynamic response to nonwords, consistent with prolonged processing in this area during the lexical decision task. Phonological processing areas such as superior temporal and angular gyrus showed no delay or width difference for rotated stimuli. These results suggest that phonological routes but not semantic routes to the lexicon can proceed regardless of stimulus orientation. This study demonstrates the utility of estimating hemodynamic delay and width in addition to amplitude allowing for more quantitative measures of brain function such as mental chronometry.

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Author information

Author/s: Bellgowan, P S F (PS); Saad, Z S (ZS); Bandettini, P A (PA);

Affiliation: Laboratory of Brain and Cognition and Scientific and Statistical Computing Core, National Institute of Mental Health, Bethesda, MD 20892, USA. psfb(-atsign-)nih.gov

Journal and publication information

Publication Type: Journal Article; Research Support, U.S. Gov't, P.H.S.

Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A), published in United States. (Language: eng)

Reference: 2003-Feb; vol 100 (issue 3) : pp 1415-9

Dates: Created 2003/02/05; Completed 2003/03/18; Revised 2008/11/20;

PMID: 12552093, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

Comments and Corrections

CommentIn: Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2177-9. (PMID: 12606715)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Brain Mapping
Hemodynamics
Humans
Magnetic Resonance Imaging - methods
Male

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