Using functional magnetic resonance imaging (fMRI) to explore brain function: cortical representations of language critical areas



Pre-operative determination of the dominant hemisphere for speech and speech associated sensory and motor regions has been of great interest for the neurological surgeons. This dilemma has been of at most importance, but difficult to achieve, requiring either invasive (Wada test) or non-invasive methods (Brain Mapping). In the present study we have employed functional Magnetic Resonance Imaging (fMRI) to observe and delineate regional brain activations during execution of language related tasks. Our healthy volunteers comprised of 10 right-handed males (handedness being ascertained by “Snyder-Harris Handedness Inventory”) all speaking Persian as their native language. All the subjects performed two consequent language tasks namely “Word Generation” and” Reverse Word Reading”. The visual stimulation was performed employing a video projector and the presentation software, while the brain activity was monitored and studied by fMRI. The stimuli were given during the activation period, while the asterix had been used as the blank (rest period). The subject response was internal speech. The fMRI method employed, was Echo Planar Imaging (EPI) using FSL as the analyzing software. The Hardware comprised of 1.5 Tesla GE brand MRI scanner. The brain regions involved language processing could be successfully and prominently activated with the aforementioned tasks (percent activity 1.2% and P<0.005). In all of the ten subjects being examined, these regions were exclusively located in the left hemisphere corresponding to Broca, Wernicke, and Exner areas. These promising results may be of value to determine the dominant hemisphere by a non-invasive method, or as an adjunct to conventional methods of Electrocortical Mapping and Wada test. Besides, the presented visual tasks could specifically activate the traditional language centers even those known to be involved in writing (Exner area). Estimation of the exact sensitivity and specificity of the methods requires employing a gold standard methods and larger subject populations.