AJDRAJNR - American Journal of Neuroradiology

Published ahead of print on September 20, 2007
doi: 10.3174/ajnr.A0632
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American Journal of Neuroradiology 28:1715-1721, October 2007
© 2007 American Society of Neuroradiology

FUNCTIONAL

Nonlinear Changes in Brain Activity During Continuous Word Repetition: An Event-Related Multiparametric Functional MR Imaging Study

R.E. Hagenbeeka, S.A.R.B. Romboutsb, D.J. Veltmand, J.W. Van Strienf, M.P. Witterc, P. Scheltense and F. Barkhofa

a Department of Radiology, VU University Medical Center, Amsterdam, the Netherlands
b Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, the Netherlands
c Department of Anatomy and Embryology, VU University Medical Center, Amsterdam, the Netherlands
d Department of Psychiatry, VU University Medical Center, Amsterdam, the Netherlands
e Department of Neurology, VU University Medical Center, Amsterdam, the Netherlands
f Department of Psychology, Erasmus University, Rotterdam, the Netherlands

Please address correspondence to F. Barkhof, MD, Department of Radiology, VU University Medical Center, PO Box 7057, 1007 MB Amsterdam, the Netherlands; e-mail f.barkhof{at}vumc.nl

BACKGROUND AND PURPOSE: Changes in brain activation as a function of continuous multiparametric word recognition have not been studied before by using functional MR imaging (fMRI), to our knowledge. Our aim was to identify linear changes in brain activation and, what is more interesting, nonlinear changes in brain activation as a function of extended word repetition.

MATERIALS AND METHODS: Fifteen healthy young right-handed individuals participated in this study. An event-related extended continuous word-recognition task with 30 target words was used to study the parametric effect of word recognition on brain activation. Word-recognition–related brain activation was studied as a function of 9 word repetitions. fMRI data were analyzed with a general linear model with regressors for linearly changing signal intensity and nonlinearly changing signal intensity, according to group average reaction time (RT) and individual RTs.

RESULTS: A network generally associated with episodic memory recognition showed either constant or linearly decreasing brain activation as a function of word repetition. Furthermore, both anterior and posterior cingulate cortices and the left middle frontal gyrus followed the nonlinear curve of the group RT, whereas the anterior cingulate cortex was also associated with individual RT.

CONCLUSION: Linear alteration in brain activation as a function of word repetition explained most changes in blood oxygen level–dependent signal intensity. Using a hierarchically orthogonalized model, we found evidence for nonlinear activation associated with both group and individual RTs.






Copyright © 2008 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X