1. General explaining about EEG Mehran Ahmadlou 86133001

2. تاريخچه: در سال 1924 براي اولين بار توسط فيزيولوژيست آلماني «هانس برگر» ثبت و نام‌گذاري شد.

3. Why neocortex ? First, the activity of one neuron is too small to be recorded. To be visible on the scalp, electrical activity must involve thousands of neurons acting synchronously. The neocortex has a high density of neurons, which facilitates their synchronous activation. Second, it is not enough to act synchronously. Electrical activity is visible only if the activity of the underlying neurons adds up. To add up the activity must be generated by parallel neurons. The neocortex is composed of pyramidal cells aligned in parallel. Third, the electric and magnetic field decrease with the distance from the source. The neocortex is closer to recording sensors.

4. the 10-20 international system It is based on anatomical location and on percentage of distance among these points giving the 10 or 20% in the system name. The original 10-20 system has only nineteen electrodes but has been extended to accommodate more than 200 electrodes. 128 channels In this system the electrodes' locations are related to specific brain areas. For example, electrodes C3 and C4 are above the motor cortex

5. F (frontal), C (central), T (temporal), P (posterior), and O (occipital).

6. Each EEG signal can therefore be correlated to an underlying brain area. A better correlation can be obtained by registering the electrode's locations with MRI of the subject's head. Electrical Recording with Differential Amplifiers : Reference and “ Active ” Electrodes Bipolar and “ Monopolar ” Montages Bias of the Average Reference

7. B. اندازه‌گيري تک‌قطبي ( Unipolar ) A. اندازه‌گيري دوقطبي ( Bipolar )

8. Characterization of EEG Activity General EEG frequencies : eta: 13-30 Hz (desynchronized) alpha: 8-12 Hz (synchronized) theta: 3.5-7.5 Hz (synchronized) delta: < 3.5 Hz (synchronized) Lower frequencies are usually higher amplitude (“synchronized”) activity

9. فرکانس‌هاي مختلف :‌ DELTA 0.5 تا 3 هرتز خواب بسيار عميق در شيرخوارگان کمتر از 6 ماه موج غالب است هنگام حل مسائل دشوار دلتاي با دامنه‌ي زياد: ناتوانايي‌هاي يادگيري صدمات مغزي

10. فرکانس‌هاي مختلف :‌ THETA 4 تا 7 هرتز بي‌هوشي، هيپنوتيزم، روياي عميق شهود و خلق کودکان و نوجوانان تتا با دامنه‌ي زياد: ناتوانايي‌هاي يادگيري پاسخ متقابل کند افسردگي و اضطراب کمبود اکسيژن در خون

11. فرکانس‌هاي مختلف :‌ ALPHA 8 تا 12 هرتز هشياري کامل مطالعه و تعمق Meditation ( با چشم بسته بهتر آشکار مي‌شوند ) آلفا با دامنه‌ي زياد: Daydreamers مصرف ماري‌جوانا بي‌خوابي

12. فرکانس‌هاي مختلف :‌ BETA 15 تا 22 هرتز تفکر تمرکز حل مساله آلفا با دامنه‌ي زياد: Obsessive-Compulsive Disorder (OCD) Anxiety Disorders

13. فرکانس‌هاي مختلف :‌ GAMMA 35 تا 42 هرتز فعاليت‌هاي ذهني زياد (ادراک، ترس، حل مسائل و...) تجارب متعالي

14. The amplitude of the normal EEG can vary between approximately -100 and +100 µV, and its frequency ranges up to about 40 Hz.

16. کاربردها تشخيص صرع (epilepsy) کمک به تشخيص آسيب‌هاي مغزي –ضربات، تومورها، ورم مغز (encephalitis)، mental retardation ، تشخيص‌هاي روان‌شناسي –schizophrenia ، paranoia ، افسردگي‌هاي ناشي از اختلالات مغزي مانند پارکينسون و آلزايمر بررسي فعاليت مغز هنگام بيهوشي در اعمال جراحي بررسي خواب و ناهنجاري‌هاي خواب تشخيص مرگ مغزي

17. Figure 7.5 (a) Four types of EEG waves. Figure 7.5 (b) When the eyes are opened, alpha waves disappear.

18. Figure 7.5 (c) Different types of epilepsy yield abnormal waveforms. (From Guyton, A. C. Structure and Function of the Nervous System, 2nd. Ed. Copyright  1972 by W. B. Saunders. Reprinted by permission of W. B. Saunders.)