During polysomnography, a rhythm of 4-7 Hz is recorded over the hippocampus while a subject is awake and actively exploring the environment. Which of the following best describes this rhythm and its functional context?
- A Alpha rhythm during relaxed wakefulness with eyes closed
- B Theta rhythm during active exploration and spatial navigation ✓
- C Beta rhythm during focused mental concentration
- D Delta rhythm during slow-wave sleep
Correct answer: B. Theta rhythm during active exploration and spatial navigation
Explanation
Hippocampal theta rhythm (4-7 Hz) is prominently observed during active exploration, spatial navigation, and encoding of spatial information in rodents and humans. It is distinct from alpha rhythm (8-13 Hz, posterior dominant, eyes closed), beta rhythm (14-30 Hz, active concentration), and delta rhythm (0.5-4 Hz, slow-wave sleep). Theta is considered important for temporal coding and memory encoding processes.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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