Human brain language areas identified by functional magnetic resonance imaging

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Brain Imaging

Background:

• Classical models of language localization are based on lesion data.
• These models identify specific brain regions (Broca's and Wernicke's areas) for language functions.
• Advances in neuroimaging allow for direct investigation of language processing in vivo.

Purpose of the Study:

• To identify candidate language processing areas in the intact human brain using functional magnetic resonance imaging (fMRI).
• To define language broadly, encompassing phonological and lexical-semantic functions.
• To compare language processing with a control task involving nonlinguistic auditory stimuli.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed on 30 right-handed subjects.
• A language activation task involved phonetic and semantic analysis of spoken words.
• Control task involved perceptual analysis of nonlinguistic sounds; data were averaged into a standard stereotaxic space.

Main Results:

• Cortical activation for language processing was strongly lateralized to the left cerebral hemisphere.
• Language network involved frontal, temporal, and parietal lobes.
• Identified language areas extended beyond classical Wernicke and Broca areas, including temporoparietal and prefrontal regions.

Conclusions:

• Findings support and refine classical models of language localization.
• Demonstrated extensive left prefrontal involvement in receptive language functions.
• Suggests a broader network of brain regions supports language processing than previously defined by lesion studies.