Which of the following EEG frequencies can be seen during an arousal from sleep?

Which of the following EEG frequencies can be seen during an arousal from sleep?

• A. All of the above
• B. Alpha
• C. Theta
• D. Any frequency over 16, excluding sleep spindles

Answer: (A)

During an arousal from sleep, the EEG shifts abruptly from slower sleep rhythms to faster, wake-like activity. This desynchronization can present as a mix of frequencies: alpha waves can appear as the brain nears wakefulness, theta may be seen during the transition, and higher-frequency activity in the beta range (and even gamma) can occur as arousal intensifies. Sleep spindles are not present during arousal, helping distinguish it from deeper sleep stages. Because alpha, theta, and higher-frequency activity can all occur during arousal (with spindles absent), the option describing all of these frequencies best captures what can be seen.

During an arousal from sleep, the EEG shifts abruptly from slower sleep rhythms to faster, wake-like activity. This desynchronization can present as a mix of frequencies: alpha waves can appear as the brain nears wakefulness, theta may be seen during the transition, and higher-frequency activity in the beta range (and even gamma) can occur as arousal intensifies. Sleep spindles are not present during arousal, helping distinguish it from deeper sleep stages. Because alpha, theta, and higher-frequency activity can all occur during arousal (with spindles absent), the option describing all of these frequencies best captures what can be seen.