Further, the results of group-averaging analyses are generally interpreted through reverse inference from anatomical locations to function 4, 5, but because of the variability mentioned above, combined with the functional heterogeneity of the association cortex, locations in a common brain space cannot be meaningfully linked to function (see 6 for a discussion of this issue for ‘Broca’s area’).Īn alternative analytic approach, which circumvents voxel-wise brain averaging, is known as ‘functional localization’ 3, 7. However, because of the well-established inter-individual variability in the locations of functional areas in the association cortex 1, 2, activations do not align well across individuals, leading to low sensitivity and functional resolution 3. A common analytic approach in fMRI language studies is to average activation maps voxel-wise in a common brain space and perform statistical inference across individuals in each voxel. More meaningful comparisons of findings across studies should increase robustness and replicability in language research.įMRI is an invaluable non-invasive tool for illuminating the brain’s architecture, especially for human-unique abilities like language. This atlas enables estimating the probability that any given location in a common space belongs to the language network, and thus can help interpret group-level activation peaks and lesion locations, or select voxels/electrodes for analysis. To bridge these disjoint approaches, we created a probabilistic functional atlas using fMRI data for an extensively validated language localizer in 806 individuals. Because of its greater sensitivity, functional resolution, and interpretability, functional localization is gaining popularity, but it is not always feasible, and cannot be applied retroactively to past studies. An alternative approach relies on identifying language areas in each individual using a functional ‘localizer’. This approach has limitations: because of inter-individual variability in the locations of language areas, any given voxel/vertex in a common brain space is part of the language network in some individuals but in others, may belong to a distinct network. One relies on averaging activations across individuals. Two analytic traditions characterize fMRI language research.
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