Word rhyming as a probe of hemispheric language dominance with functional magnetic resonance imaging.

OBJECTIVE: The goal of this study was to create a probe of hemispheric dominance for language using functional magnetic resonance imaging.
BACKGROUND: Surgical candidates for anterior temporal lobectomy often undergo the Wada test to determine language laterality. The Wada test is invasive and cannot localize intrahemispheric language areas when surgical resection encroaches on eloquent cortex. We report the results of a stimulation paradigm that activates regions involved in motor language, language phonology, and visual word form perception.
METHOD: Five right-handed healthy subjects underwent blood oxygen level-dependent functional magnetic resonance imaging. Subjects alternately viewed consecutive word pairs, indicating when the words rhymed, and consecutive pairs of line arrays, indicating when the arrays matched by responding "Yes" or "No" using a button box.
RESULTS: Subjects performed both tasks with equivalent accuracy. Compared with the nonverbal control task, word rhyming produced greater left-hemisphere activation than right-hemisphere activation. Foci of rhyme-related activation were found in the left Brodmann's area (BA) 44 (Broca's area), left dorsolateral prefrontal cortex (BA 9/46 and BA 8/9), left middle temporal gyrus (BA 22), and left fusiform gyrus (BA 37) in the posterior basal temporal lobe. Activation associated with the control task was present in the right parietal area and in right temporal and left parietal regions.
CONCLUSIONS: Subvocal word rhyming activates dominant perisylvian cortical regions and may be useful for determining hemispheric language dominance and for functional mapping of language cortex.