Investigating Binding of Item and Context (BIC) in patients with drug-resistant temporal lobe epilepsy and hippocampal sclerosis: A behavioural and voxel-based morphometry (VBM) study

Memory impairments are widely recognized in epilepsy patients. The current study focused on associative memory, and in particular on Binding of Item and Context (BIC) in patients with drug-resistant temporal lobe epilepsy (TLE) and left (N= 25) or right hippocampal sclerosis (HS) (N=15). Considering the pivotal role of the hippocampus in BIC, we hypothesise that patients with functional (i.e., epilepsy) and structural (i.e., sclerosis) alteration involving the hippocampus should present BIC deficits compared to healthy controls (HC) (N=30). Furthermore, using a VBM approach, we investigate structural correlates of BIC in this kind of patients. To do that, participants underwent a two-phase associative memory experiment. In the first phase, participants were presented with different naturalistic scenes, each with a target object embedded to learn object/scene associations. In the second phase of the experimental paradigm, the participant's BIC was tested by recalling the correct object/scene associations. As hypothesised, significant differences in behavioural scores were found between the healthy controls and both pathological groups, meaning that patients showed lower BIC scores compared to HC. Regarding the VBM results, we found a broad structural network associated with BIC within the HC group, confirming that frontal areas are also involved in memory processing. This result does not replicate in patient groups, indicating a possible network disruption. Furthermore, a significant association between BIC and left fusiform gyrus grey matter density emerged in the left HS group that was not seen in healthy controls. We can speculate that this result should indicate a compensation mechanism, whereas left HS patients should rely on the fusiform gyrus to compensate for other areas. Our results confirm an associative memory deficit in TLE patients with HS, and VBM analyses showed structural network disruption in this kind of patient, confirming that epilepsy is a compl