Cortical reorganization for calculation in patients with left temporal lobe epilepsy

Abstract

Objective To observe the brain regions activated during calculation in patients with left temporal lobe epilepsy (TLE) and in normal subjects. Methods Functional magnetic resonance imaging (fMRI) was applied. Sixteen right-handed persons with left TLE were selected as the left TLE group, and sixteen healthy volunteers were recruited as a control group. The fMRI data was collected as each subject performed simple additions, subtractions and abdication subtractions. Statistical parametric mapping was used to compare the activated brain regions between the two groups. Results The error rate in the calculations was significantly higher in the left TLE group, and their average reaction time was significantly longer. There were aslo significant differences between the two groups in terms of brain activation patterns. Compared with the control group, the left TLE group exhibited hypo-activity in regions such as the left paracentral lobule, the posterior central gyrus, the bilateral inferior parietal lobule, the left angular gyrus, the bilateral supramarginal gyrus, the left middle frontal gyrus, the left superior gyrus, and also in the bilateral posterior cingulate, insular lobule, superior and inferior temporal gyrus, right hippocampus, parahippocampal gyrus, thalamus and cerebellum. The TLE subjects exhibited hyper-activity in the bilateral superior parietal lobule, the bilateral anterior cingulate, as well as in the right, middle and inferior frontal gyrus. Conclusion Our results support a significant functional reorganization of calculation-related neuronal networks within and between the hemispheres in TLE patients. The frontal and parietal lobes may play a compensatory role in the reorganization of the calculation function. Task-related fMRI technology can provide useful information for non-invasive assessment of mathematical computing and cognitive function in TLE patients. Key words: Temporal lobe epilepsy; Computation; Cognition; Functional magnetic resonance imaging