A comparison of five fMRI protocols for mapping speech comprehension systems
Article first published online: 30 MAY 2008
Wiley Periodicals, Inc. © 2008 International League Against Epilepsy
Volume 49, Issue 12, pages 1980–1997, December 2008
How to Cite
Binder, J. R., Swanson, S. J., Hammeke, T. A. and Sabsevitz, D. S. (2008), A comparison of five fMRI protocols for mapping speech comprehension systems. Epilepsia, 49: 1980–1997. doi: 10.1111/j.1528-1167.2008.01683.x
- Issue published online: 1 DEC 2008
- Article first published online: 30 MAY 2008
- Accepted April 22, 2008; Early View publication May 30, 2008.
- Temporal lobe
Aims: Many fMRI protocols for localizing speech comprehension have been described, but there has been little quantitative comparison of these methods. We compared five such protocols in terms of areas activated, extent of activation, and lateralization.
Methods: fMRI BOLD signals were measured in 26 healthy adults during passive listening and active tasks using words and tones. Contrasts were designed to identify speech perception and semantic processing systems. Activation extent and lateralization were quantified by counting activated voxels in each hemisphere for each participant.
Results: Passive listening to words produced bilateral superior temporal activation. After controlling for prelinguistic auditory processing, only a small area in the left superior temporal sulcus responded selectively to speech. Active tasks engaged an extensive, bilateral attention, and executive processing network. Optimal results (consistent activation and strongly lateralized pattern) were obtained by contrasting an active semantic decision task with a tone decision task. There was striking similarity between the network of brain regions activated by the semantic task and the network of brain regions that showed task-induced deactivation, suggesting that semantic processing occurs during the resting state.
Conclusions: fMRI protocols for mapping speech comprehension systems differ dramatically in pattern, extent, and lateralization of activation. Brain regions involved in semantic processing were identified only when an active, nonlinguistic task was used as a baseline, supporting the notion that semantic processing occurs whenever attentional resources are not controlled. Identification of these lexical-semantic regions is particularly important for predicting language outcome in patients undergoing temporal lobe surgery.