Introduction: Recently the importance of the left ventral anterior temporal lobe (vATL) in language/semantic cognition has been highlighted from several studies. We aimed to clarify its role in semantic cognition by performing neuropsychological testing in patients with temporal lobe epilepsy (TLE) who underwent resection of the language dominant vATL.
Methods: We studied 10 TLE patients who underwent presurgical evaluation with subdural grid implantation over the left vATL. The language/semantic region of vATL, namely, the basal temporal language area (BTLA) was defined by 50 Hz electrical stimulation with 5-6 language/semantic tasks. All patients underwent subtemporal amygadalo-hippocampectomy (AH) leaving the white matter pathways to/from the basal areas intact (Miyamoto,2004). All underwent WMS-R and WAB batteries before/after surgery. Detailed batteries on semantic cognition, such as synonym judgment, were performed post-operatively when the core BTLA (>4 tasks impairment by stimulation) was resected.
Results: 2-11 BTLA electrodes were identified per patient. One patient underwent additional corticetomy of the core BTLA in the anterior fusiform gyrus. Immediately after surgery, this patient developed moderate anomia and a difficulty in reading and writing Kanji words. Although WAB score recovered to the normal range in 1 year after surgery, accuracy rate of low imageability words in synonym judgment remained low even 3 years after surgery. 3 patients with tailored corticectomy of non-core BTLA did not show any anomia. In 7 patients, the score of verbal memory in WMS-R improved postoperatively.
Conclusions: Semantic outcome after resection of the core BTLA indicates a major role of BTLA in the semantic aspect of language function. Together with absence of anomia and improvement of verbal memory in other patients, improvement of semantic cognition in this patient suggests importance of the intact white matter connections in reorganization of the semantic or ventral language network.