Implementation of clinically relevant and robust fMRI-based language lateralization: Choosing the laterality index calculation method

• Published in: PloS one Vol. 15; no. 3; p. e0230129
• Main Authors: Brumer, Irène, De Vita, Enrico, Ashmore, Jonathan, Jarosz, Jozef, Borri, Marco
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.03.2020; Public Library of Science (PLoS)
• Subjects: Activation; Adult; Amobarbital; Batch processing; Biology and Life Sciences; Biomedical engineering; Brain - physiology; Brain mapping; Brain Mapping - methods; Cohort Studies; Correlation coefficient; Correlation coefficients; Diagnostic imaging; Engineering; Female; Functional Laterality - physiology; Functional magnetic resonance imaging; Hemispheric laterality; Humans; Language; Magnetic resonance; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Male; Mathematical analysis; Medical imaging; Medicine and Health Sciences; Methods; Middle Aged; Neuroimaging; Neurosurgery; Neurosurgery - methods; Physical Sciences; Rankings; Research and Analysis Methods; Robustness; Social Sciences; Surgery; Values; Young Adult; United Kingdom > UK
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0230129

The assessment of language lateralization has become widely used when planning neurosurgery close to language areas, due to individual specificities and potential influence of brain pathology. Functional magnetic resonance imaging (fMRI) allows non-invasive and quantitative assessment of language lateralization for presurgical planning using a laterality index (LI). However, the conventional method is limited by the dependence of the LI on the chosen activation threshold. To overcome this limitation, different threshold-independent LI calculations have been reported. The purpose of this study was to propose a simplified approach to threshold-independent LI calculation and compare it with three previously reported methods on the same cohort of subjects. Fifteen healthy subjects, who performed picture naming, verb generation, and word fluency tasks, were scanned. LI values were calculated for all subjects using four methods, and considering either the whole hemisphere or an atlas-defined language area. For each method, the subjects were ranked according to the calculated LI values, and the obtained rankings were compared. All LI calculation methods agreed in differentiating strong from weak lateralization on both hemispheric and regional scales (Spearman's correlation coefficients 0.59-1.00). In general, a more lateralized activation was found in the language area than in the whole hemisphere. The new method is well suited for application in the clinical practice as it is simple to implement, fast, and robust. The good agreement between LI calculation methods suggests that the choice of method is not key. Nevertheless, it should be consistent to allow a relative comparison of language lateralization between subjects.