Mapping of Language-and-Memory Networks in Patients With Temporal Lobe Epilepsy by Using the GE2REC Protocol

Sonja Banjac; Elise Roger; Emilie Cousin; Chrystèle Mosca; Lorella Minotti; Alexandre Krainik; Philippe Kahane; Monica Baciu

doi:10.3389/fnhum.2021.752138

Mapping of Language-and-Memory Networks in Patients With Temporal Lobe Epilepsy by Using the GE2REC Protocol

Front Hum Neurosci. 2022 Jan 6:15:752138. doi: 10.3389/fnhum.2021.752138. eCollection 2021.

Authors

Sonja Banjac¹, Elise Roger¹, Emilie Cousin^{1

2}, Chrystèle Mosca³, Lorella Minotti³, Alexandre Krainik², Philippe Kahane³, Monica Baciu¹

Affiliations

¹ Université Grenoble Alpes, CNRS LPNC UMR 5105, Grenoble, France.
² Université Grenoble Alpes, UMS IRMaGe CHU Grenoble, Grenoble, France.
³ Université Grenoble Alpes, Grenoble Institute of Neuroscience 'Synchronisation et modulation des réseaux neuronaux dans l'épilepsie' & Neurology Department, Grenoble, France.

Abstract

Preoperative mapping of language and declarative memory functions in temporal lobe epilepsy (TLE) patients is essential since they frequently encounter deterioration of these functions and show variable degrees of cerebral reorganization. Due to growing evidence on language and declarative memory interdependence at a neural and neuropsychological level, we propose the GE2REC protocol for interactive language-and-memory network (LMN) mapping. GE2REC consists of three inter-related tasks, sentence generation with implicit encoding (GE) and two recollection (2REC) memory tasks: recognition and recall. This protocol has previously been validated in healthy participants, and in this study, we showed that it also maps the LMN in the left TLE (N = 18). Compared to healthy controls (N = 19), left TLE (LTLE) showed widespread inter- and intra-hemispheric reorganization of the LMN through reduced activity of regions engaged in the integration and the coordination of this meta-network. We also illustrated how this protocol could be implemented in clinical practice individually by presenting two case studies of LTLE patients who underwent efficient surgery and became seizure-free but showed different cognitive outcomes. This protocol can be advantageous for clinical practice because it (a) is short and easy to perform; (b) allows brain mapping of essential cognitive functions, even at an individual level; (c) engages language-and-memory interaction allowing to evaluate the integrative processes within the LMN; (d) provides a more comprehensive assessment by including both verbal and visual modalities, as well as various language and memory processes. Based on the available postsurgical data, we presented preliminary results obtained with this protocol in LTLE patients that could potentially inform the clinical practice. This implies the necessity to further validate the potential of GE2REC for neurosurgical planning, along with two directions, guiding resection and describing LMN neuroplasticity at an individual level.

Keywords: fMRI mapping; language; memory; preoperative assessment; surgery; temporal lobe epilepsy.