Question

Stage 2 sleep is defined by the presence of

• A. \( \text{spikes and slow waves} \)
• B. \( \text{sleep spindles and K complexes} \)
• C. \( \text{rapid eye movements} \)
• D. \( \text{1 to 2 Hz delta frequencies} \)

Hint:

To remember the defining features of sleep stages, focus on the unique EEG patterns:

• N1 (Drowsiness) Theta waves, vertex sharp waves, slowing of alpha rhythm.
• N2 (Light Sleep) **Sleep spindles** and **K complexes** are the defining features.
• N3 (Deep/Slow-Wave Sleep) Predominance of high-amplitude **delta waves** (slow waves).
• REM (Dreaming Sleep) Low-voltage, mixed-frequency EEG (similar to awake state), **rapid eye movements**, and muscle atonia.

Understanding these distinct EEG patterns is fundamental for sleep staging in polysomnography.

Answer 1

The Correct Option is B

To solve this problem, we need to identify the characteristics of Stage 2 sleep in the context of sleep cycles.

1. Understanding Stage 2 Sleep:

- Stage 2 Sleep: Stage 2 is a phase of non-REM (Rapid Eye Movement) sleep. It is characterized by specific EEG (electroencephalogram) patterns that distinguish it from other sleep stages.

- During Stage 2 sleep, two key phenomena are observed in the EEG:

• Sleep Spindles: These are short bursts of oscillatory brain activity visible on an EEG, typically lasting for about 0.5-2 seconds and occurring at a frequency of 12-16 Hz.
• K Complexes: These are high-amplitude waves that typically occur as single large waves in response to external stimuli, often lasting for about 0.5 seconds.

2. Analyzing the Options:

- Option 1: "Spikes and slow waves" – This is more characteristic of other stages, like Stage 3 or Stage 4, where delta waves (slow waves) are more prominent.

- Option 2: "Sleep spindles and K complexes" – This is the correct answer. These two features are the hallmark characteristics of Stage 2 sleep.

- Option 3: "Rapid eye movements" – These are typically associated with REM sleep, not Stage 2.

- Option 4: "1 to 2 Hz delta frequencies" – These are typically observed in Stage 3 and Stage 4, not Stage 2.

Final Answer:

The correct answer is \( \text{sleep spindles and K complexes} \).