Các điện cực được dán nhãn theo địa điểm gần đúng của họ trên bán cầu não (F = phía trước, T = thời gian, C = trung tâm, P = đỉnh, và O = chẩm, z chỉ định đường giữa), còn lại là chỉ định bởi các số lẻ và bên phải số chẵn. Một dòng parasagittal chạy giữa nasion và inion và một đường hào quang giữa các điểm preauricular đo. | Electrophysiological Techniques 139 FIGURE 7-4. The 10-20 International System of Electrode Placement. Electrodes are labeled according to their approximate locations over the hemispheres F frontal T temporal C central P parietal and O occipital z designates midline left is indicated by odd numbers and right by even numbers. A parasagittal line running between the nasion and inion and a coronal line between the preauricular points is measured. Electrode placements occur along these lines at distances of 10 and 20 of their lengths as illustrated. In most clinical laboratories the Fpz and Oz electrodes are not placed but are instead used only as reference points. Fp1 is placed posterior to Fpz at a distance equal to 10 of the length of the line between Fpz-T3-Oz F7 is placed behind Fp1 by 20 of the length of that line. O1 is placed anterior to Oz at a distance equal to 10 of the length of the line between Oz-T3-Fpz T5 is placed anterior to O1 by 20 of the length of that line. F3 is placed halfway between Fp1 and C3 along the line created between Fp1-C3-O1 P3 is placed halfway between O1 and C3 along that same line. Right hemisphere electrodes are placed in similar fashion. Reference electrodes in this case placed on the ears are labeled A1 and A2. tion digitization and computer-assisted methods permit quantitative electroencephalographic analyses that are not possible through visual inspection alone Hughes and John 1999 . These methods include quantified analysis of the frequency composition of the EEG over a given period spectral analysis analysis of absolute and relative amplitude pV cycle second and power pV2 cycle sec-ond within a frequency range or at each channel coherence correlation between activity in two channels phase relationships in the timing of activity between two channels or symmetry between homologous pairs of electrodes Hughes and John 1999 Neylan et al. 1997 Nu-wer 1990 Thatcher 1999 . Values derived from quantitative electroencephalographic .
