Pre- and postsurgical memory performance in patients with temporal and frontal lobe epilepsy

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Epilepsy surgery is an effective treatment option in patients with temporal lobe epilepsy (TLE) and in patients with frontal lobe epilepsy (FLE) who are often difficult to treat medically. One of the main side effects of epilepsy surgery are postsurgical deteriorations of memory functions. To date, it is not possible to reliably predict postsurgical changes of mnestic functions from presurgical data in individual patients.Our project aims at improving the understanding of presurgical mnestic functions and their underlying neural correlates. It will contribute to a better understanding of postsurgical memory changes caused by epilepsy surgery in patients with TLE and FLE. In a first step, presurgical memory performance and the extent of postsurgical changes will be compared between TLE and FLE patients. In this context, the effect of lesion localisation on memory performance will be the main focus of analysis. We will use the method of voxel-based symptom-lesion mapping to detect lesion and resection sites that are specifically associated with pre- and postsurgical memory impairments. Secondly, a multimodal fMRI learning paradigm will be used prior to surgery to identify memory-related neural correlates that are specifically associated with temporal or frontal brain lesions. Presurgical fMRI activation associated with memory tasks will be correlated with presurgical and postsurgical neuropsychological measures of memory. We aim at improving the prediction of postsurgical memory changes in TLE and FLE patients. For this purpose, we will develop a multifactorial prediction model. Besides epilepsy-related clinical factors and neuropsychological measures, this model will contain presurgically assessed MRI-based parameters, i.e., fMRI activations from our learning paradigm, from a verbal fluency fMRI task, data on functional connectivity based on the default mode network, diffusion tensor imaging and voxel-based morphometry data. After testing the predictive value of each of these parameters, we will combine the best predictors to a weighted multifactorial model. In summary, the project will contribute to the understanding of mnestic functions and postoperative changes in surgically treated TLE and FLE patients. It will give generalisable insights into the contribution of temporal and frontal brain areas to memory processes by investigating these "human lesion models" prior and after brain surgery.