Abstracts

Rationale: Cognitive dysfunction in patients with epilepsy may stem from neurophysiological changes related to seizures or to anti-epileptic drugs (AEDs). Mismatch Negativity (MMN) is a well known index of temporal lobe function which is not affected by attention or motivation. This is expecially true for the response for vowel-speech change, which has been used for investigating preattentive language function. In this study, we utilized a vowel-speech MMN paradigm to objectively evaluate cognitive function in patients with temporal lobe epilepsy (TLE). Methods: We examined 13 TLE patients (six female, 11 right-handed; age 22-50 years; age of onset between 3-25 years). Five patients were seizure free for more than 2 years. Eight patients had at least 10 seizures a year prior to this study. The epileptic focus was in the left hemisphere in four patients, right in one, bilateral in one, and unclear in the remaining patients. Six patients took either zero or one AED, four patients took two AEDs, and three patients took more than three AEDs. Control data were collected from nine age-matched healthy participants (six female, all right-handed). The stimuli were Japanese vowel-speech (`a` as standard and `o` as deviant). The MMN was recorded from four midline (Fz, Cz, Pz, Oz) and bilateral mastoid electrodes, and at least 100 responses for deviation were analyzed for each participant. Participants were instructed to watch video screen showing a cartoon story during sessions and to ignore sounds. We evaluated the peak amplitude, mean amplitude and peak latency at each electrode between 50 and 200 ms to the change in vowel-speech sounds and ERP parameters were compared by ANOVA. Results: There was a trend that patients with frequent seizures have lower mean amplitude at Fz (p=0.06)(Figure 1). There was also a tendency that the patients with more AEDs had low amplitude at Fz (Figure 2). Larger asymmetries of mean amplitude at the mastoid were found in patients compared to control participants. Conclusions: Vowel -speech MMN in TLE patients is affected with seizure frequency and AEDs suggesting that TLE patients have dysfunction in pre-attentive language processing.