Purpose: We investigated the efficiency of lexical and semantic processing in participants with right temporal lobe epilepsy (TLE). We also mapped brain activation patterns during this processing using functional magnetic resonance imaging (fMRI).
Methods: Ten participants with right TLE and 12 healthy controls were studied. All participants underwent a 3T fMRI investigation during a lexical decision task (LDT). Stimuli included words (concrete and abstract) and nonwords. Lexical and semantic processing were examined by comparing behavioural (response times and accuracy) and fMRI data associated with words and nonwords (lexicality) and with concrete and abstract words (concreteness), respectively.
Results: Both groups exhibited significant behavioural effects of lexicality and concreteness. However, right TLE participants showed a larger lexicality effect and had longer response times compared to controls. The right TLE group exhibited different patterns of fMRI activation compared to controls. Specifically, increased left hemispheric activation was seen, particularly in the left inferior frontal gyrus (IFG) during nonword processing.
Discussion: Right TLE negatively affects the efficiency of lexical processing and lexical decision making. Increased involvement of the left IFG suggests that compensation occurs in the cortical networks involved in lexical processing occurred as a result of pathology in the right hemisphere.
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