According to polarity convention for EEG, when is the deflection upward?

According to polarity convention for EEG, when is the deflection upward?

• A. Input 2 is equal to input 1
• B. Input 2 is more negative than input 1
• C. Input 1 is more negative than input 2
• D. Input 1 is more positive than input 2

Answer: (C)

In EEG, the polarity convention is based on comparing the electrical potentials between two input electrodes, typically referred to as input 1 and input 2. When input 1 has a more negative potential than input 2, the difference in potential results in an upward deflection on the EEG tracing. This is because the EEG system is set to record the voltage difference, and when one input is more negative than the other, it indicates that the first electrode (input 1) is receiving a stronger negative charge compared to the reference (input 2). Therefore, this upward deflection signifies that electrical activity at input 1 is more negatively charged than that at input 2, which is represented as a positive voltage change. Understanding this concept is essential for interpreting EEG waveforms accurately, as it helps technologists make sense of various brain activities and states captured during an EEG study.

In EEG, the polarity convention is based on comparing the electrical potentials between two input electrodes, typically referred to as input 1 and input 2. When input 1 has a more negative potential than input 2, the difference in potential results in an upward deflection on the EEG tracing. This is because the EEG system is set to record the voltage difference, and when one input is more negative than the other, it indicates that the first electrode (input 1) is receiving a stronger negative charge compared to the reference (input 2).

Therefore, this upward deflection signifies that electrical activity at input 1 is more negatively charged than that at input 2, which is represented as a positive voltage change. Understanding this concept is essential for interpreting EEG waveforms accurately, as it helps technologists make sense of various brain activities and states captured during an EEG study.