Abstracts

Rationale: Damage to the bilateral ATL leads to impaired semantic performance in Alzheimer's disease, semantic dementia (SD) and herpes simplex encephalitis (HSE), suggesting that the bilateral ATL is a core region for semantic representation. However, it is often suggested that semantic memory is intact in TLE patients. The formal evidence base is very sparse, however, because TLE patients are often not tested for semantic impairments. This new Spanish semantic battery includes a variety of tasks that tap on semantic memory. In addition, by including difficult semantic information at a specific level, the battery is sensitive to small semantic impairments. We expect TLE patients to show semantic impairments but the pattern will be less clear compared to patient groups with bilateral ATL damage. The endpoint of this study is to investigate the impact of anterior temporal lobe (ATL) lobectomy in patients with temporal lobe epilepsy (TLE) on semantic processing using a new Spanish semantic battery. Methods: We evaluated 24 patients (14 with left and 10 with right temporal lobe epilepsy), 13 men and 11 women, and 30 controls. Mean age was 42.5 years-old (range 18-65), with 34.4 years (range 7-60) since epilepsy onset. Span time between surgery and evaluation was 4.9 years (range 1-9). All patients had undergone surgery (standard ATL lobectomy) due to refractory mesial temporal lobe epilepsy. They performed two expressive tasks (on basic and specific level items), two comprehensive tasks (synonym judgement and the Pyramids and Palm tree task), WAIS matrices test and Rey auditory verbal learning test. The results were compared with an age and education matched control group. The study was done at least 6 months after the surgery. In contrast to most neuropsychological tests, we did not only collect accuracy data, but also reaction time data. This allows us to obtain a clearer picture of the impairment pattern in TLE patients. Results: We ran a MANOVA including all tasks and three groups (i.e., left TLE, right TLE patients and control participants). The outcome tells us that the performance on the semantic battery significantly differs between the three groups (F(24,76), = 2.48, p = 0.001; Wilk's ? = 0.314, ?2 = 0.4.39). Post hoc test revealed that left TLE patients performed worse on all tasks compared to control participants. In addition, naming performance on specific items was particularly poor in the left TLE group. In contrast, the accuracy of right TLE patients was not significantly worse compared to control participants. However, when looking at the reaction time data it was clear that right TLE patients performed slower compared to controls but faster compared to left TLE patients. Conclusions: Patients were more impaired on the semantic tasks compared to controls. Left TLE patients performed worse and slower on all tasks compared to control participants. However, even though the accuracy did not seem to be affected in the right TLE group, they performed slower on most tasks. This shows that it is important to look at reaction time data in addition to accuracy. These outcomes show that the new Spanish semantic battery is sensitive to semantic impairments in TLE patients. Funding: No funding was received for this abstract