Abnormalities of lexical and semantic processing in left temporal lobe epilepsy: An fMRI study

• Published in: Epilepsia (Copenhagen) 2011-11, Vol.52 (11), p.2013-2021
• Main Authors: Jensen, Elizabeth J., Hargreaves, Ian S., Pexman, Penny M., Bass, Adam, Goodyear, Bradley G., Federico, Paolo
• Format: Article
• Language: English
• Subjects: Adult; Anticonvulsants. Antiepileptics. Antiparkinson agents; Biological and medical sciences; Brain; Brain - physiopathology; Brain mapping; Case-Control Studies; Cortex; Data processing; Decision making; Epilepsy; Epilepsy, Temporal Lobe - complications; Epilepsy, Temporal Lobe - physiopathology; Executive function; Female; Functional magnetic resonance imaging; Functional morphology; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Hippocampal sclerosis; Hippocampus; Humans; Information processing; Language; Language Disorders - etiology; Left temporal lobe epilepsy; Lexical processing; Magnetic Resonance Imaging; Male; Medical sciences; Middle Aged; Nervous system (semeiology, syndromes); Neuroimaging; Neurology; Neuropharmacology; Neuropsychological Tests; Pharmacology. Drug treatments; Psycholinguistics; Sclerosis; Semantic processing; Semantics; Temporal lobe; Temporal variations; Young Adult
• ISSN: 0013-9580; 1528-1167
• DOI: 10.1111/j.1528-1167.2011.03258.x

Summary Purpose:  We examined the efficiency of lexical and semantic processing and associated brain activation using functional magnetic resonance imaging (fMRI) in patients with left temporal lobe epilepsy (TLE). Methods:  Twenty patients with left TLE (10 with hippocampal sclerosis, the HS group; and 10 with nonlesional MR scans, the NL group) and 12 healthy controls underwent an event‐related fMRI analysis during a lexical decision task (LDT). Lexical and semantic processing were examined by comparing behavioral and imaging data associated with words and nonwords (lexicality) or with concrete and words (concreteness). Key Findings:  Although the control group showed greater activation associated with word stimuli than with nonword stimuli in a bilateral language network, both TLE groups showed greater activation for nonword stimuli than word stimuli, including greater activation of inferior frontal language areas (bilaterally in the HS group and left‐lateralized in the NL group). The TLE groups also exhibited differential activation patterns during the processing of and concrete words compared to controls, and compared to each other. For words, in particular, the HS group showed activation of frontal areas typically associated with executive functions, whereas the NL group showed activation of more posterior semantic processing regions. Significance:  These results suggest that left TLE is associated with altered functional organization of cortical networks involved in lexical and semantic processing. In addition, the organization observed varies as a function of hippocampal pathology.