Semantic Processing Impairment in Patients with Temporal Lobe Epilepsy.

Amanda G. Jaimes-Bautista,Yaneth Rodríguez-Agudelo,Mario Rodríguez-Camacho,Iris E. Martínez-Juárez

doi:10.1155/2015/746745

Abstract

The impairment in episodic memory system is the best-known cognitive deficit in patients with temporal lobe epilepsy (TLE). Recent studies have shown evidence of semantic disorders, but they have been less studied than episodic memory. The semantic dysfunction in TLE has various cognitive manifestations, such as the presence of language disorders characterized by defects in naming, verbal fluency, or remote semantic information retrieval, which affects the ability of patients to interact with their surroundings. This paper is a review of recent research about the consequences of TLE on semantic processing, considering neuropsychological, electrophysiological, and neuroimaging findings, as well as the functional role of the hippocampus in semantic processing. The evidence from these studies shows disturbance of semantic memory in patients with TLE and supports the theory of declarative memory of the hippocampus. Functional neuroimaging studies show an inefficient compensatory functional reorganization of semantic networks and electrophysiological studies show a lack of N400 effect that could indicate that the deficit in semantic processing in patients with TLE could be due to a failure in the mechanisms of automatic access to lexicon.

Highlights

Temporal lobe epilepsy (TLE) constitutes 80% of focal epilepsies and is the most frequent form in adults [1, 2]
The results of this study suggest that semantic processing is sensitive to left temporal dysfunction; the question remains open as to whether the absence of the N400 effect may be associated with deficits in access and retrieval of semantic information or with the attentional processes necessary to carry out the semantic categorization task
This study showed that semantic processing impairment in patients with TLE is related to deficiencies in the automatic activation mechanisms, and in addition, it seems that patients do not benefit from the use of strategies for retrieval of information

Summary

Introduction

Temporal lobe epilepsy (TLE) constitutes 80% of focal epilepsies and is the most frequent form in adults [1, 2]. Semantic memory is important because it contains the knowledge that allows individuals to communicate, represent, and mentally operate situations, objects, and relations with the world, which otherwise are not available to the senses. It allows the identification of events and use of general knowledge that forms the basis of our knowledge of the world [25]. The main objective of this paper is to review recent research regarding the consequences of TLE on semantic memory, considering neuropsychological, electrophysiological, and neuroimaging findings. The search was made in PubMed using as key words: temporal lobe epilepsy, hippocampus, semantic memory and semantic processing, event related potentials, and N400 component and functional magnetic resonance imaging

Semantic Memory

Semantic Memory and Temporal Lobe Epilepsy

Findings

Conclusions