Recurring Dreams: Are they in your head… or your brain?

You wake up and it has happened again—that recurring anxiety dream. For me, I’m on the sidelines of the volleyball court, the game is starting, and I don’t have my socks or shoes on. My coach is yelling at me to get in the game and I stumble to put my socks on as fast as possible, to no avail. The dream is so vivid and happens so often that if I close my eyes, I can reimagine it. In fact, I just had it last night. But why? I don’t feel particularly anxious about anything today. But maybe it’s my presentation on Wednesday… or my interview on Thursday… or my flight to California on Saturday. All of which I don’t think I am anxious about, but is my subconscious stepping in when I go to bed? How much of our daily anxieties show up to haunt us when we fall asleep? Are there any theories in neuroscience that can we draw upon that may support this notion of anxiety dreams?

Hobson’s activation-synthesis hypothesis asserts that our dreaming is merely a product of random activation of the brain during REM sleep. We then take this nonsense and consciously try to make sense of it both during sleep and upon waking. Hobson hypothesizes that dreams are meaningless and rejects Freud’s idea of the selection of our dream content. Freud theorized that dream content was based on our internal desires, sometimes suppressed, that we experience throughout the day, also known as his theory of wish fulfillment. Hobson’s dismissal of Freudian dreaming also aligns with Santiago Ramon y Cajal’s in his claim that dreams are random activation of seldom used networks with physiological importance only.

Hobson theorizes that dreaming is a result of chaotic activity in the brainstem that occurs during REM sleep. Specifically, signals are generated by the Pontine brainstem that move to the lateral Geniculate body of the thalamus and finally in the Occipital cortex, and are therefore known as PGO waves. The signal is triggered by the absence of serotonin (5HT), an inhibitory neurotransmitter. When present, serotonin hyperpolarizes motor neurons in the pons. Therefore, when the serotonergic cells are not activated, the transition into REM sleep initiates the PGO waves.(read more at http://thebrain.mcgill.ca/flash/a/a_11/a_11_cr/a_11_cr_cyc/a_11_cr_cyc.html)
The amount of PGO waves has been shown to correlate with the amount of REM sleep and more specifically, the amount of eye movement during REM sleep. This evidence suggests a relationship between PGO waves and dreaming. Because of their unique pattern, these waves may also provide a marker for sleep scientists to objectively identify when a person is dreaming based on brain activity.

Hobson’s theory asserts that the “lawlessness” of dream construction is the cause for our bizarre dreaming. Further, he says that much of our dream plot selection is due to mere chance, which he claims is advantageous as it ensures an equal likelihood for all content to be depicted in dreaming. This theory could also provide advantages for memory consolidation so as to ensure memories were encoded via an unbiased system, not allowing favorable memories to be the only ones we remember.

However, the assertion that dream content is random and completely dependent on the chaotic activation of the brainstem is problematic. Two strong cases can be made against Hobson’s random-activation hypothesis: dreams are often coherent and certain themes are more represented than others, specifically in terms of recurring dreams. One specific piece of evidence refuting this claim comes from people going through drug withdrawal who often have vivid, recurring drug dreams. Recurring dreams strongly oppose Hobson’s random selection of dream content theory because random activation does not lend itself to creating specific dreams that happen on nightly occurrences. However, people tend to report having the same dreams over and over again. Although this cannot be empirically proven, it does provide compelling evidence against Hobson’s random theory.

Another component of dreaming that does not align with Hobson’s theory of bizarreness is that dreams are often coherent. Most people, who remember and can recount their dreams, claim to dream about particular people, places and events. Chaotic activity in the brainstem should result in incomprehensible visual imagery. However, people are often able to vividly describe the visual content of their dreams which are not mere flashes of colors or lights.

Although Hobson’s activation synthesis hypothesis is a well-known and well-regarded theory in dream research, it is important to realize its flaws and those dreams that it cannot explain. The future of dream research then, must not rely on theories that have been accepted as facts, and rather, look to improve upon and perhaps consolidate existing theories. This research however, is contingent on the advancements in technology that may allow us to investigate the dreams without depending solely on self-reports as our data.

 

Reference:

Hobson, J.A. (2009). REM sleep and dreaming: towards a theory of protoconsciousness. Nature Reviews Neuroscience, 10 (11), 803-813.

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