Functional MR Imaging of Cerebral Auditory Cortex with Linguistic

ABSTRACT

PURPOSE: To obtain preliminary data for understanding the central auditory neural pathway by means of functional MR imaging (fMRI) of the cerebral auditory cortex during linguistic and non-linguistic auditory stimulation. MATERIALS AND METHODS: In three right-handed volunteers we conducted fMRI of auditory cortex stimulation at 1.5 T using a conventional gradient-echo technique (TR/TE/flip angle 80/60/40 degree). Using a pulsed tone of 1000 Hz and speech as non-linguistic and linguistic auditory stimuli, respectively, images-including those of the superior temporal gyrus of both hemispheres-were obtained in sagittal plases. Both stimuli were separately delivered biaurally or monoaurally through a plastic earphone. Images were activated by processing with homemade software. In order to analyze patterns of auditory cortex activation according to type of stimulus and which side of the ear was stimulated, the number and extent of activated pixels were compared between both temporal lobes. RESULTS: Biaural stimulation led to bilateral activation of the superior temporal gyrus, while monoaural stimulation led to more activation in the contralateral temporal lobe than in the ipsilateral. A trend toward slight activation of the left (dominant) temporal lobe in ipsilateral stimulation, particularly with a linguistic stimulus, was observed. During both biaural and monoaural stimulation, a linguistic stimulus produced more widespread activation than did a non-linguistic one. CONCLUSION: The superior temporal gyri of both temporal lobes are associated with acoustic-phonetic analysis, and the left (dominant) superior temporal gyrus is likely to play a dominant role in this processing. For better understanding of physiological and pathological central auditory pathways, further investigation is needed.