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.
Highlights
Studies on temporal lobe epilepsy (TLE), the most common form of epilepsy, cite problems with episodic memory and naming or verbal fluency among the most frequent concomitant cognitive deficits (Bell et al, 2011; Bartha-Doering and Trinka, 2014; Zhao et al, 2014; Jaimes-Bautista et al, 2015; TramoniNegre et al, 2017; Dutta et al, 2018)
Case Studies Patients To illustrate the potential of the GE2REC protocol at an individual level in clinical practice, we present two case studies of left TLE (LTLE) patients who underwent left anterior temporal lobectomy and had different ages of seizures onset, epilepsy duration, seizure frequency, and the number of antiepileptic drugs
The first one was to explore neuroplasticity of the language and memory network, in line with which we explored the reorganization of language-andmemory network (LMN) in LTLE patients by comparing them with healthy controls (HC)
Summary
Studies on temporal lobe epilepsy (TLE), the most common form of epilepsy, cite problems with episodic memory and naming or verbal fluency among the most frequent concomitant cognitive deficits (Bell et al, 2011; Bartha-Doering and Trinka, 2014; Zhao et al, 2014; Jaimes-Bautista et al, 2015; TramoniNegre et al, 2017; Dutta et al, 2018). A meta-analysis reported that 44% of left TLE (LTLE) patients faced verbal memory and 34% naming decline (Sherman et al, 2011). The main goal of preoperative assessment is to perform a cost-benefit analysis and evaluate the risks of cognitive decline versus the potential seizure freedom (Massot-Tarrús et al, 2019). In addition to clinical and neuropsychological characteristics of patients that are essential in the presurgical assessment (Baxendale et al, 2013; Jarcušková et al, 2020), functional MRI (fMRI) can predict postoperative cognitive performance and decline, and it is frequently used for preoperative assessment (Binder et al, 2010; Bonelli et al, 2010; Sidhu et al, 2015; Strandberg et al, 2017; You et al, 2019). Studies show clinical application of functional connectivity (Bettus et al, 2010; Pravatà et al, 2014; Tracy and Doucet, 2015; DeSalvo et al, 2020; Foesleitner et al, 2021) and effective connectivity (Vaudano et al, 2021)
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