EEG Recording and AnalysisEEG recor

EEG Recording and AnalysisEEG recordings (NeuroScan) were taken from 64 tin electrodesites with the reference on the left mastoid and re-referencedoff-line to the average of the left and right mastoids. Thehorizontal electro-oculogram (EOG) was recorded from twoadditional bipolar electrode sites placed 1 cm lateral to theouter canthi of each eye. The vertical EOG was recorded fromelectrode sites below and above the left eye. The impedancefor all electrode sites was maintained below 5 k. EEG andEOG activities were amplified with a bandpass of 0.01–100 Hzand sampled at 500 Hz/channel. The data were analyzed offline.Ocular artifacts were corrected by NeuroScan software (Semlitschet al., 1986). Data were filtered with a low-pass filter at 30 Hz(24 dB/octave). The EEG was segmented in epochs of 1000 ms,time-locked to stimuli (the verb words) onset and included a200 ms pre-stimulus baseline. Trials contaminated by amplifierclipping, bursts of electromyographic activity, or peak-to-peakdeflection exceeding ±75 µV were excluded from averaging.According to the grand average ERP waveforms and topographicmap (see Figure 1), the following nine posterior electrodesites were selected for statistical analysis: left (CP3, P3, PO3);midline (CPz, Pz, POz); right (CP4, P4, PO4). The N400component was calculated mean amplitudes within 250–500 mswindow.