EEG sensitivity directly influences how the electrical signals from the brain are displayed on the EEG tracing. Sensitivity is measured in microvolts per millimeter (μV/mm), and it determines how much electrical activity is needed to produce a specific vertical movement on the EEG paper or digital display.

1. Higher Sensitivity (Lower μV/mm)

Example: 1 μV/mm, 3 μV/mm

  • Effect on Waveform: The waveform appears larger or more prominent for a given electrical signal. A smaller voltage (fewer microvolts) is required to move the pen or the digital trace.
  • Use Case: Higher sensitivity is useful for detecting low-amplitude signals or subtle brain activity. It enhances the visibility of smaller, more delicate waveforms, especially in conditions where the signals are weak.

2. Lower Sensitivity (Higher μV/mm)

Example: 7 μV/mm, 15 μV/mm

  • Effect on Waveform: The waveform appears smaller because a larger voltage (more microvolts) is needed to move the pen or trace by the same amount. This results in a more compressed representation of the signal.
  • Use Case: Lower sensitivity is useful when dealing with high-amplitude signals or when you need to reduce excessive deflections, such as when large spikes or discharges dominate the signal.

3. Standard Sensitivity (7 μV/mm)

This is the most common setting, offering a balance between sensitivity and resolution. It works well for routine EEG recordings where average brain wave activity needs to be monitored.

Practical Considerations:

  • High-Amplitude Discharges: When there are very high-amplitude discharges (e.g., seizures), the waveform may become too large to be clearly visualized. In such cases, raising the sensitivity (decreasing μV/mm) can make it easier to see the shape and structure of these large signals.
  • Low-Amplitude Signals: For weaker signals, lowering the sensitivity (increasing μV/mm) helps in making these smaller signals more discernible.
  • Children's EEG: Children's brains often produce higher-amplitude signals compared to adults, so using higher sensitivity (lower μV/mm) may be more effective for their EEG.

Summary:

  • Lower μV/mm (higher sensitivity): Larger waveforms, useful for detecting small signals.
  • Higher μV/mm (lower sensitivity): Smaller waveforms, useful for reducing large spikes or discharges.

Always remember to reset the sensitivity to its standard value after adjusting for specific circumstances to avoid missing important activity.