Brain Functional Areas Related To Digital Calculations: A Functional Magnetic Resonance Imaging Study

Objective: To localize functional areas related to digital calculations with fMRI, to investigate the roles of these areas for digital calculations, and to postulate the relationship among the functional areas.Materials and Methods: 28 right-handed healthy subjects received anatomical FLAIR T1WI and GRE-EPI fMRI with a 1.5T whole body MRI scanner (GE, 1.5T twinspeed infinity with Excite I). Experimental tasks include subvocal number reading, simple calculation, complex calculation and proximity judgement. Following block design, 3 trial blocks and 3 contrast blocks were performed alternatively and experimental procedures were monitored by RTIP. Realigning, normalizing and smoothing were performed using SPM99 for fMRI data; activation foci were superposed on high-resolution T1WI. Conjunction analysis and intergroups analysis were performed.Results: For subvocal number reading task, significant activations were observed in the left posterior part of inferior frontal gyrus, left angular gyrus, bilateral medial frontal gyrus, bilateral occipital lobes and cerebellums. Dorsallateral of left prefrontal cortex, bilateral premotor area, posterior part of inferior frontal gyrus, medial frontal gyrus, and cortex around intraparietal sulcus, posterior part of inferior temporal gyrus, bilateral occipital lobes and cerebellums were all activated during simple calculation, complex calculation and proximity judgment task. Right dorsal lateral part of prefrontal cortex was activated only in the complex calculation and proximity judgment task. Bilateral cortex around intraparietal sulcus(especially inferior parietal lobules) were the most obvious activated regions in three experiments. Compared with simple calculation, extent and magnitude of functional areas increased obviously in complex calculation. During performing proximity judgment task, activation areas overlapped to some extent with those during simple calculation task, but bilateral posterior part of inferior frontal gyrus, premotor areas and cortex surrounding intraparietal sulcus showed more obvious activation.Conclusion: fMRI can readily detect brain function areas related to digital calculations. Digital calculations involve functional areas that related to subvocal number reading, and may contain more complex cognitive activation. Multiple functional areas are related to digital calculations, including conjunction of temporal and occipital lobes, posterior part of inferior frontal gyrus, cortex surrounding intraparietal sulcus, dorsal lateral of the prefrontal cortex, premotor area, medial frontal gyrus and anterior part of cingulate g yrus, these areas may work together as a whole in processing arithmetic problems. Inferior parietal lobules may be the nerve center for calculation. Working memory play a important role in digital calculation. All digital calculations may have similar neural networks.Part II: The Laterality of Brain Functional Areas Related to DigitalCalculations Revealed byfMRIObjective: To reveal the laterality of brain functional areas during performing digital c alculations w ith f MRI, t o a ssess t he relationship b etween 1 aterality and handedness as well as type of arithmetical tasks. Postulate the possible reasons for laterality.Materials and Methods: 20 right-handed and 7 left-handed healthy subjects received anatomical FLAIR T1WI and GRE-EPI fMRI with a 1.5T whole body MRI scanner (GE, 1.5T twinspeed infinity with Excite I). Experimental tasks include simple calculation, complex calculation and proximity judgment. Following block design, 3 trial blocks and 3 contrast blocks were performed alternatively and experimental procedures were monitored by RTP. Realigning, normalizing and smoothing were performed using SPM99 for fMRI data, activation foci were superposed on high-resolution T1WI. Conjunction analysis was performed. Numbers of activative voxels were used to calculate laterality index, LI=(Vl-Vr)/(Vl+Vr), where Vl and Vr are numbers of activative voxels for the symmetry brain functional areas in bilateral hemisphere. LI...