fMRI memory assessment in healthy subjects: a new approach to view lateralization data at an individual level
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We present a comprehensive and clinically applicable fMRI test—including both a verbal and a visuospatial task—for assessment of hemispheric specific memory in the medial temporal lobe (MTL). fMRI data was collected from 15 healthy right-handed volunteers. Whole-brain activation was analyzed as well as activation in two regions of interest: the MTL and the anterior speech area. Laterality indices (LI) and LI-curves were calculated using the LI toolbox of Wilke and Lidzba, 2007. The fMRI paradigms successfully visualized memory-related activity in the MTL, the verbal memory measure also provided information of language lateralization. Eleven subjects showed left lateralized verbal encoding in the MTL, visuospatial memory activation was divided equally between left and right, and 14/15 subjects had left lateralized language. Lateralization data at the group level were consistent with previous studies, but a variety of activation effects were found at the individual level indicating differences in strategy during verbal and visuospatial processing. Further studies using the presented method are needed to determine its clinical usefulness.
KeywordsMedial temporal lobe Verbal episodic memory Mental navigation task Laterality index Laterality curves Visuospatial memory
This research was financially supported by the University Hospital in Lund, Sweden, and by grant from the Swedish Research Council (projects no. 421-2005-1678). The authors thank the staff at the Department of Radiology at the University Hospital of Lund, Sweden, for their contribution to the research. They also thank Anthony Waites, Magnus Lindgren and Peter Höglund for their contributions to this paper.
Maria Strandberg was the recipient of the GlaxoSmith Kline Epilepsy Scholarship 2007.