Sunday, September 13, 2009

How can we have a terrifying dream?

terrifying dream
Today I was very curious about why we often experience terrifying dreams when we are stressed and preoccupied. I also opened high-wire, the site that provides many medical journals. Here is a quote from one of the journals that explain why we can have nightmares.

Studies have shown that various limbic structures are differentially active during dreaming. Maquet et al. used positron emission tomography (PET) and statistical parametric mapping to ascertain which structures are active during REM sleep. Using 30 healthy, right-handed males, they demonstrated that, over three nights of observed sleep, the hippocampus was relatively inactive, whereas the cingulate gyrus and, especially, the amygdaloid complex demonstrated increased cerebral blood flow and elevated EEG activity. Braun et al. also used PET data, with 10 healthy male subjects, to determine that limbic and paralimbic structures are highly active during REM sleep. Amygdalofugal pathways to the right parietal operculum, entorhinal cortex, thalamic nuclei, dorsal mesencephalon, and pontine tegmentum were also found to be activated during REM sleep. These areas, in addition to the visual association cortices, were suggested to function as a "closed unit" during REM sleep.

In terms of general limbic function, the hippocampus appears to be responsible for the processing of "cool," episodic, explicit experiences, whereas the amygdala is active during emotional activity that is often implicit and tied to conditional fear and aggression responses. It appears that the amygdala and its connections with the hypothalamus and lower brainstem areas become engaged when an individual is under stress. This limbic structure also facilitates the organism's efficiency in processing threatening information and quickly initiates response mechanisms to successfully avoid threat. In other words, the "hot" emotional processing system that is activated during waking hours to assist in the detection of threat is also highly active during REM sleep.

From these quotations, we may conclude that the hippocampus will be activated when we're relaxed and having a pleasant experience. In contrast, the amygdala would be activated when we are in a distressed condition. It turned out that the amygdala activation was still continuing when we're asleep. This is what causes terrifying dreams.

So, how to stop a terrifying dream? Maybe we need to stop dreaming and start action, so we are not afraid anymore!

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