Electroencephalograms (EEGs)

• Electroencephalograms (EEGs)


  Measures electrical activity in the brain. Electrodes are placed on the scalp which detect small electrical charges resulting from the activity of brain cells. When electrical signals from the different electrodes are graphed over a period of time the resulting representation is called an EEG. EEG data can be used to detect various brain disorders or to diagnose other disorders.
• What are the 4 basic types of wave detected on an EEG

  1. Alpha Waves - When a person is awake and relaxed, rhythmical alpha waves are recorded.
  2. Beta Waves - When someone is physiologically aroused, their EEG pattern shows low amplitude, fast frequency beta waves.
  3. Theta Waves - As a person moves from light sleep to deep sleep, alpha waves decrease and are replaced first by lower frequency theta waves and then delta waves.
  4. Delta Waves - Also present in sleep.
• One strength of the EEG technique is that it provides a recording of brain activity in real time. This means that the researcher can accurately measure a particular activity or tasks effects on the brain.
• An EEG is useful in clinical diagnosis, e.g by recording the abnormal activity associated with epilepsy. Epileptic seizures are caused by disturbed brain activity, which means that the normal EEG reading suddenly changes. This helps diagnose whether someone having seizures has epilepsy.
• Because an EEG can only detect the activity in superficial regions of the brain, it cannot reveal what is going on in deeper regions such as the hypothalamus or hippocampus. Electrodes can be implanted in non-humans to achieve this, but it is not ethically permissible to do this with humans as the would be too invasive.
• Electrical activity can be picked up by several neighbouring electrodes, therefore the EEG signal is not useful for pinpointing the exact source of an activity. As a result, it does not allow researchers to distinguish between activities originating from different parts of the brain.