10-20 System
A standardized method for electrode placement on the scalp used in electroencephalography (EEG) and transcranial stimulation procedures.
The 10-20 system represents a internationally recognized methodology for standardizing the placement of electrodes on the human scalp, primarily used in electroencephalography and neurofeedback applications.
Historical Development
Developed by Herbert Jasper and Herbert H. Jasper in 1958, the system emerged from the need to create consistency in brain mapping research and clinical practice. Prior to its introduction, electrode placement varied significantly between laboratories, making cross-study comparisons challenging.
Anatomical Framework
The system derives its name from the proportional distances between electrode sites:
- Measurements use percentages (10% or 20%) of the total distance between specific anatomical landmarks
- Key reference points include the nasion (bridge of nose) and inion (occipital protuberance)
- Lateral measurements reference the preauricular points on each ear
Electrode Positioning
Primary Positions
- Frontal (F)
- Central (C)
- Parietal (P)
- Temporal (T)
- Occipital (O)
Naming Convention
- Even numbers (2,4,6,8) denote right hemisphere positions
- Odd numbers (1,3,5,7) denote left hemisphere positions
- 'z' refers to midline positions
- Example: Fz represents the midline frontal position
Clinical Applications
The system finds extensive use in:
- Clinical EEG monitoring
- Brain-Computer Interface development
- Neurofeedback interventions
- Transcranial Magnetic Stimulation applications
Modern Variations
Several extensions to the original system exist:
- The 10-10 system (increasing density of electrode positions)
- The 5-5 system (higher density mapping)
- Modified versions for infant head sizes
Significance in Research
The standardization provided by the 10-20 system has enabled:
- Reproducible research protocols
- Consistent clinical assessments
- Compatible data sharing between institutions
- Development of automated EEG Analysis tools
Limitations and Considerations
While widely adopted, users should consider:
- Individual anatomical variations
- Head size differences
- Need for precise measurement tools
- Training requirements for accurate placement
The 10-20 system continues to serve as the foundation for modern brain mapping techniques, enabling both research advancement and clinical applications in neuroscience and related fields.