Question

According to the International 10/20 system to measure EEG, even number electrodes denotes which side of the brain?

• A. \( \text{Left} \)
• B. \( \text{Top} \)
• C. \( \text{Bottom} \)
• D. \( \text{Right} \)

Hint:

A useful mnemonic for remembering the 10/20 system's numbering convention is: "Even on the Right, Odd on the Left." This simple phrase helps to quickly recall which side of the brain corresponds to even or odd electrode numbers. Understanding this system is fundamental for anyone working with EEG data or setting up EEG experiments.

Answer 1

The Correct Option is D

To solve this problem, let's examine the International 10-20 system for EEG electrode placement and understand what even-numbered electrodes signify.

1. What is the International 10-20 System?

The International 10-20 System is the standardized method for placing electrodes on the scalp for EEG recordings. It ensures consistent placement across different patients and recording sessions by using specific anatomical landmarks and proportional measurements.

2. Electrode Numbering Convention

The system follows a specific numbering pattern to identify electrode positions:

• Odd numbers (1,3,5,7...): Represent electrodes placed on the left hemisphere of the brain
• Even numbers (2,4,6,8...): Represent electrodes placed on the right hemisphere of the brain
• Letter "Z": Denotes midline electrodes that are placed centrally

3. Practical Examples

This numbering system creates clear left-right distinctions:

• F3 (left frontal) vs F4 (right frontal)
• C3 (left central) vs C4 (right central)
• P3 (left parietal) vs P4 (right parietal)
• O1 (left occipital) vs O2 (right occipital)

4. Explanation of the Options

- Left: Incorrect - this is represented by odd numbers
- Top: Incorrect - vertical position is indicated by letter codes, not numbers
- Bottom: Incorrect - not indicated by numbering system
- Right: Correct - even numbers consistently denote the right hemisphere

5. Why This Standardization Matters

The consistent numbering system allows:

• Accurate comparison of EEG recordings between sessions
• Precise localization of brain activity abnormalities
• Clear communication between healthcare professionals
• Reliable research data collection

6. Additional System Features

The 10-20 system also includes:

• Letter codes for brain regions (F=frontal, T=temporal, etc.)
• Precise measurement techniques based on skull landmarks
• Extensions like the 10-10 system for higher density recordings

7. Final Answer:

In the International 10-20 system for EEG, even-numbered electrodes denote the right side of the brain.