Cortical hyperarousal in individuals with frequent nightmares

Area of Science:

• Neuroscience
• Sleep Medicine
• Psychiatry

Background:

• Nightmares are prevalent in general and psychiatric populations, often linked to nocturnal arousal signs like elevated heart rate and high-frequency electroencephalographic (EEG) activity.
• The distinction between these arousal characteristics as stable traits versus state indicators during nightmares remains unclear.

Purpose of the Study:

• To investigate whether increased high-frequency EEG activity during sleep is a trait in individuals with frequent nightmares or a state-dependent phenomenon.
• To assess the impact of imagery rehearsal therapy (IRT) on sleep architecture, spectral power, and cortical hyperarousal in frequent nightmare sufferers.

Main Methods:

• A comparative study involving a frequent nightmare group (NM; n=30) and healthy controls (n=27) over four nights in a sleep laboratory.
• The NM group underwent six sessions of IRT between the second and third nights.
• Sleep architecture and spectral power (beta and gamma frequencies) were analyzed, comparing groups and comparing nightmare vs. non-nightmare nights within the NM group, as well as pre- and post-therapy.

Main Results:

• The NM group exhibited significantly higher overall beta and low gamma power throughout the night compared to controls.
• This difference in high-frequency activity was not observed when comparing nightmare occurrence nights to non-nightmare occurrence nights within the NM group.
• Post-therapy, the NM group showed a reduction in low gamma activity specifically during rapid eye movement (REM) sleep.

Conclusions:

• Cortical hyperarousal, characterized by elevated beta and low gamma EEG activity, appears to be a stable trait in individuals experiencing frequent nightmares.
• Imagery rehearsal therapy (IRT) demonstrates the capacity to modulate this hyperarousal, offering a potential mechanism for its therapeutic effects.
• These findings suggest that targeting high-frequency EEG activity could be a viable strategy for developing improved nightmare treatments.