Memory retrieval in temporal lobe epilepsy is related to functional segregation of the mesiotemporal structures.

OBJECTIVE

We analyzed the impact of temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS) on functional connectivity (FC) between mesiotemporal structures. Functional connectivity modifications related to word retrieval were investigated.

METHODS

High-density EEG of 21 patients with TLE with HS (12 left TLE and 9 right TLE) and 10 healthy controls (HCs) were recorded during a verbal subsequent memory paradigm. Electroencephalography data were reconstructed into the source space and FC was calculated from the source activity of regions of interest.

RESULTS

A significant decrease in FC between the right- and left-sided mesiotemporal structures in TLE was observed. The decrease was significant only with words that were correctly recognized. The decrease in interhemispheric FC between mesiotemporal structures was found in the 8- to 20-Hz frequency range in both left and right TLE.

SIGNIFICANCE: The decreased FC between the mesiotemporal structures in TLE is a condition for successful performance of a memory retrieval task. The successful memory retrieval in TLE is related to functional segregation of lesional from nonlesional mesiotemporal structures. This decrease was absent in non-successful responses.