A neuron’s primary mode of messaging with its neighbouring neurons is through electrical impulses. So, it is safe to say that electrical patterns generated by this neuron-talk represent the health and wellbeing of the brain. Any glitches in these impulses indicate neurological conditions like seizures or encephalopathies, for example.
Just as we cannot see electricity in wires, we cannot see the brain’s internal electrical activity. However, science has advanced to develop an instrument – the electroencephalograph (EEG)- that can detect and record these subtle impulses. (Note: electroencephalography is the technique, and the electroencephalogram is the record produced by the instrument)
“It [EEG instrument] measures the electrical activity and impulses of the brain which is then converted to a graph that is easily readable on a computer screen and a paper,” explains Dr Manoj Pardhe, a consultant neurophysiologist from Mumbai. He says that the EEG converts the brain’s electrical potential into waveforms.
He explains that the EEG detects 4 important types of waves:
- Alpha waves: 8 -12 waves per second (Hz).
- Beta waves: 13-19 Hz
- Theta waves – 3-7 Hz (high amplitude)
- Delta waves – 1-3 Hz.
Read more about brain waves in a technique called neurofeedback training in our magazine.
EEG is a safe and non-invasive method to test the brain’s electrical activity. When someone gets an EEG, the expert places around 18 electrodes all over their scalp using a connecting gel/paste. The person’s hair must be completely dry, devoid of oil, and rough to prevent the electrodes from moving. These electrodes are connected to an amplifier, which is connected to a screen. The screen shows the brain’s electrical activity as a graph (similar to an ECG graph).
The experts follow certain standard activation protocols like making the person breathe deeply and quickly flashing light into their eyes. This helps to check photosensitivity or how the brain reacts to light.
Read more: When miss is a hit: the perils of misdiagnosing epilepsy
The expert then reads this graph to see if there is any unusual activity. This helps detect conditions like epilepsy, encephalopathies, and Creutzfeldt-Jakob disease. Dr Pardhe adds that they can also tell if a person’s brain has stopped working by looking at the graph. “The EEG is usually flat [in brain-dead conditions],” he says.
