Day 2: What is EEG

Introduction
In this post, I will introduce four fundamental foundations of my research: the brain, what EEG is, and its applications.

1. Brain
From the system level perspective, the brain is organized into different parts with specific properties.
For better explanation i created this map.

2. The Electroencephalogram (EEG), Rhythms, and Waveforms
The combined electrical activity of the cerebral cortex is called a brain wave or rhythm. These signals change over time and often form repeating wave patterns. This happens because many brain cells (neurons) are active together.
When large groups of neurons work at the same time, they create an electrical signal strong enough to be measured from the scalp using EEG.

These brain waves can have different speeds (frequencies) and strengths (amplitudes).
EEG is very sensitive to changes in mental state. It can reflect many conditions, such as stress, alertness, calmness, deep rest, hypnosis, and sleep.

Think of a crowded football stadium. One person clapping is quiet, but when thousands of people clap together in rhythm, the sound becomes loud and clear.
EEG works in a similar way. A single neuron is too weak to measure, but when many neurons firetogether in a rhythm, their combined activity becomes strong enough to detect on the scalp.

3. EEG Recording Techniques
Electrodes captures the signal from the scalp, amplifiers bring the microvolt signals into the range where they can be digitalized accurately, A/D converter converts signals from analog to digital form, and processing/storing device stores, processes or displays recorded data.
I did a simple workflow of how it works.

4. Application: Sleep and Circadian Rhythm Disorder Investigation
Different sleep disorders show different patterns in EEG signals. These patterns reflect how the brain behaves during various stages of sleep.
To properly study sleep disorders, it is important to track how sleep stages change over time. By measuring these changes in a clear and quantitative way, EEG helps reveal problems in sleep structure, timing, and quality.
This makes EEG a valuable tool for understanding how the brain moves between wakefulness, light sleep, deep sleep, and dreaming.

Final Thoughts
The brain carries out countless functions, generating complex patterns of electrical activity. Sleep is not merely a period of rest for the body—it is an active, dynamic process driven by the brain. Remarkably, these processes can be observed and studied through EEG.
This post is the foundation of my journey: to observe, measure, and verify my understanding of how EEG reveals the brain at work.