A comparison of five fMRI protocols for mapping speech comprehension systems.
OBJECTIVE
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.
Department of Neurology, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA. jbinder@mcw.edu
Jeffrey R
JR
Binder
Sara J
SJ
Swanson
Thomas A
TA
Hammeke
David S
DS
Sabsevitz
D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000098:blood supply* / Q000502:physiology; D032882:Comprehension / Q000502:physiology*; D003194:Computer-Assisted Instruction / Q000379:methods; D003657:Decision Making / Q000502:physiology; D004192:Discrimination, Psychological; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D011578:Psycholinguistics; D012660:Semantics; D013060:Speech; D013067:Speech Perception / Q000502:physiology; D055815:Young Adult
D010100:Oxygen