Functional Reorganization Associated with Semantic Language Processing in Temporal Lobe Epilepsy Patients after Anterior Temporal Lobectomy : A Longitudinal Functional Magnetic Resonance Image Study. |
Jae Hun Kim, Jong Min Lee, Eunjoo Kang, June Sic Kim, In Chan Song, Chun Kee Chung |
1Department of Biomedical Engineering, Hanyang University, Seoul, Korea. ljm@hanyang.ac.kr 2Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea. 3Department of Psychology, Kangwon National University, Chuncheon, Korea. 4MEG Center, Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea. 5MEG Center, Department of Radiology, Seoul National University College of Medicine, Seoul, Korea. |
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ABSTRACT |
OBJECTIVE The focus of this study is brain plasticity associated with semantic aspects of language function in patients with medial temporal lobe epilepsy (mTLE). METHODS Using longitudinal functional magnetic resonance imaging (fMRI), patterns of brain activation were observed in twelve left and seven right unilateral mTLE patients during a word-generation task relative to a pseudo-word reading task before and after anterior temporal section surgery. RESULTS No differences were observed in precentral activations in patients relative to normal controls (n = 12), and surgery did not alter the phonological-associated activations. The two mTLE patient groups showed left inferior prefrontal activations associated with semantic processing (word-generation > pseudo-word reading), as did control subjects. The amount of semantic-associated activation in the left inferior prefrontal region was negatively correlated with epilepsy duration in both patient groups. Following temporal resection, semantic-specific activations in inferior prefrontal region became more bilateral in left mTLE patients, but more left-lateralized in right mTLE patients. The longer the duration of epilepsy in the patients, the larger the increase in the left inferior prefrontal semantic-associated activation after surgery in both patient groups. Semantic activation of the intact hippocampus, which had been negatively correlated with seizure frequency, normalized after the epileptic side was removed. CONCLUSION These results indicate alternation of semantic language network related to recruitment of left inferior prefrontal cortex and functional recovery of the hippocampus contralateral to the epileptogenic side, suggesting an intra- and inter-hemispheric reorganization following surgery. |
Key Words:
fMRI; Language; Epilepsy; Brain plasticity; Hippocampus |
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