Memory loss and memory reorganization patterns in temporal lobe epilepsy patients undergoing anterior temporal lobe resection, as demonstrated by pre-versus post-operative functional MRI

Whole-brain functional correlates of memory formation in mesial temporal lobe epilepsy

“…So far, few studies have examined, via whole-brain analysis, whether or to what extent TLE induces distributed changes in encoding-related activation. Extant data indicate more widespread activation in lateral temporal, frontal, and parietal regions during verbal, ( Alessio et al, 2013 , Dupont et al, 2000 , Dupont et al, 2002 , Maccotta et al, 2007 , Sidhu et al, 2013 ) and non-verbal memory encoding, ( Alessio et al, 2013 , Limotai et al, 2018 , Maccotta et al, 2007 , Sidhu et al, 2013 ) in both lTLE and rTLE patients compared with controls. Overall, additional recruitment of lateral temporal regions appears most consistent.…”

“…Additional activation in frontal areas contralateral to the epileptogenic focus has been inconsistently reported during verbal and non-verbal memory encoding in either lTLE patients, rTLE patients, or both. ( Sidhu et al, 2013 , Alessio et al, 2013 , Maccotta et al, 2007 , Limotai et al, 2018 ) Some inconsistencies might be due to the fact that existing studies had mostly rather small sample sizes and partly lacked statistical comparison with a control group, thus potentially over-interpreting descriptive differences. Furthermore, it remains unclear if reported changes in activation are specific to memory formation or reflect other unrelated cognitive processes, because most extant whole-brain studies only focused on encoding, but did not calculate subsequent memory effects.…”

“…To address these issues, we have applied a memory fMRI task of learning words, faces, and scenes. Several studies, ( Avila et al, 2006 , Bigras et al, 2013 , Cheung et al, 2006 , Detre et al, 1998 , Golby et al, 2002 , Limotai et al, 2018 , Mechanic-Hamilton et al, 2009 ) have explored encoding-related activity for complex scenes in TLE, but so far none has investigated specifically the subsequent memory effect for this material. We have also optimised scanning parameters by means of coronal slices aligned with the long axis of the hippocampus to investigate mesio-temporal and extra-temporal activation in one study.…”

A Guide to Designing a Memory fMRI Paradigm for Pre-surgical Evaluation in Temporal Lobe Epilepsy

“…Encouragingly, memory fMRI was shown to be the strongest independent predictor of post-operative memory decline compared to standard clinical outcome predictors such as age at onset of epilepsy, hippocampal volume, and pre-operative neuropsychometry (14,20). Memory fMRI has also been used to investigate post-operative memory plasticity (25)(26)(27)(28).…”

Computational Support, Not Primacy, Distinguishes Compensatory Memory Reorganization in Epilepsy

“…The degree to which TLE patients with intact memory actually differ from normal controls with similar levels of memory performance also remains unchartered and poorly understood. More specifically, in the setting of temporal lobe disease, little is known about the particular regional activations, functional connectivities, and/or network reconfigurations that appear distinctly prone to implement either changes in the primary computations or the supportive functions that drive adaptive plasticity and compensated memory output Cheung et al, 2009;Limotai et al, 2018;Sidhu et al, 2016;Tracy and Doucet, 2015).…”