Functional MRI mapping of language areas in children frequently employs a covert verb generation task. Because responses are not monitored, the relationship between fMRI activation and task performance is unknown. We compared fMRI activation during covert and overt verb generation to performance during the overt task. 15 children, ages 11-13 years, listened to concrete nouns and responded with related verbs covertly and overtly. A clustered fMRI acquisition allowed for recording of overt responses without motion artifacts. Region of interest analysis was also performed in areas that exhibited correlation between activation and performance during overt verb generation in left inferior frontal and left superior temporal gyri (along with their right hemisphere homologues). Regression analysis determined that during both covert and overt generation, left hemisphere regions showed positive correlations with average counts of verbs generated during the overt task. These results suggest that increased verb generation performance leads to increased activation. In addition, overt performance may be used as an estimator of covert performance.
"We only included 1–30 Hz in SAM analysis, which could also contribute to the discrepancies between the two modalities. As expected, significantly greater activation was identified in the bilateral primary motor cortex during the overt versus covert verb generation (C3) for both MEG and fMRI group results, which is consistent with our previous publication on this task (Vannest et al., 2010) and other investigators (Huang et al., 2002; Soros et al., 2006). An alternative explanation for the differences between fMRI and MEG composite activation maps in Fig. 2 stems from the difference in the way in which source location is computed in the two modalities. "
[Show abstract][Hide abstract] ABSTRACT: In this study we focused on direct comparison between the spatial distributions of activation detected by functional magnetic resonance imaging (fMRI) and localization of sources detected by magnetoencephalography (MEG) during identical language tasks. We examined the spatial concordance between MEG and fMRI results in 16 adolescents performing a three-phase verb generation task that involves repeating the auditorily presented concrete noun and generating verbs either overtly or covertly in response to the auditorily presented noun. MEG analysis was completed using a synthetic aperture magnetometry (SAM) technique, while the fMRI data were analyzed using the general linear model approach with random-effects. To quantify the agreement between the two modalities, we implemented voxel-wise concordance correlation coefficient (CCC) and identified the left inferior frontal gyrus and the bilateral motor cortex with high CCC values. At the group level, MEG and fMRI data showed spatial convergence in the left inferior frontal gyrus for covert or overt generation versus overt repetition, and the bilateral motor cortex when overt generation versus covert generation. These findings demonstrate the utility of the CCC as a quantitative measure of spatial convergence between two neuroimaging techniques.
Brain research 02/2012; 1447:79-90. DOI:10.1016/j.brainres.2012.02.001 · 2.84 Impact Factor
"More recently, researchers have begun to explore the influence of performance on fMRI activation during language tasks. There is evidence that task performance directly correlates with levels of brain activation in task related cortical regions (Vannest et al., 2010). Further, Yeatman et al. (2010) found that frontal regions are recruited in response to increasing task demands in children with superior language skills, suggesting that children with strong language abilities are activating higher-order brain functions with increased task complexity. "
[Show abstract][Hide abstract] ABSTRACT: Functional neuroimaging studies in healthy adults demonstrate involvement of a left-lateralized network of frontal, temporal, and parietal regions during a variety of semantic processing tasks. While these areas are believed to be fundamental to semantic processing, it is unclear if task performance is correlated with differential recruitment of these or other brain regions. The objective of this study was to identify the structures underlying improved accuracy on a semantic decision task. We also investigated whether extra-scanner performance on the Boston Naming Test (BNT) and Semantic Fluency Test (SFT), neuropsychological measures of semantic retrieval, is correlated with specific areas of activation during the semantic decision/tone decision (SDTD) fMRI task. Fifty-two healthy, right-handed individuals performed a block-design SDTD task. Regression analyses revealed that increased performance on this task was associated with activation in the right inferior parietal lobule. Higher SFT performance resulted in greater recruitment of right frontal regions; improved performance on BNT was associated with more widespread activation in prefrontal, temporal, and parietal cortex bilaterally, although this activation appeared to be stronger in the right hemisphere. Overall, our results suggest that improved performance on both intra- and extra-scanner measures of semantic processing are associated with increased recruitment of right hemispheric regions.
Brain research 09/2011; 1419:105-16. DOI:10.1016/j.brainres.2011.08.065 · 2.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Previous cross-sectional functional magnetic resonance imaging studies have shown that performance monitoring functions continue to develop well into adolescence, associated with increased activation in brain regions important for cognitive control (prefrontal cortex, anterior cingulate cortex, and parietal cortex). To date, however, the development of performance monitoring has not yet been studied longitudinally, which leaves open the question whether changes can be detected within individuals over time. In the present study, human boys and girls, between ages 8 and 27 years, performed a child-friendly rule-switch task in the scanner on two occasions ∼3.5 years apart. Change versus stability was examined using two methods: (1) repeated-measures analyses and (2) test-retest reliabilities of blood oxygenation level-dependent responses. Results showed that with increasing age, participants performed better on the task. The changes in neural activation associated with the processing of performance feedback were, however, more reliably correlated with changes in performance than with age. Test-retest reliability was at least fair to good for adults and adolescents, but poor to fair for the youngest age group. Substantially more variability was observed in the pattern and magnitude of children compared with adults, which may be interpreted as proxy for developmental change. Together, the results show that (1) change within individuals is variable, and more so for children than for adolescents and adults, and (2) performance is a better predictor for change in neural activation over time. These findings set the stage for studying developmental change in the perspective of multiple predictors, rather than solely by divisions based on age groups.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 03/2011; 31(11):4204-12. DOI:10.1523/JNEUROSCI.6415-10.2011 · 6.34 Impact Factor
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