A new theory of dreaming


EXCERPTS: Why do we dream? [...] there is still no accepted answer. Now, David M. Eagleman​​ and Don A. Vaughn​ have proposed a new theory. Their preprint article, which has not yet been peer reviewed, is called The Defensive Activation theory: dreaming as a mechanism to prevent takeover of the visual cortex. To my mind, it's a highly original and creative theory, but I'm not convinced by it.

Here's Eagleman​​ and Vaughn​'s theory in nutshell: the role of dreams is to ensure that the brain's visual cortex is stimulated during sleep. Otherwise, if the visual system were deprived of input all night long, the visual cortex's function might degrade. [...] If we are in a dark place, or it's night, we get little or no visual input. So - in theory - our visual cortex would be vulnerable to 'takeover' by other senses, every single night. Dreams, on this view, are our brain's way of defending the integrity of our visual system by keeping it active.

[...] Eagleman​​ and Vaughn's theory only makes sense if neuroplastic repurposing of the cortex happens very quickly. For the visual cortex to need defending, harmful neuroplasticity would need to occur in the space of a few hours. The authors do discuss evidence that rapid neuroplasticity can occur, but they don't show any evidence that these rapid changes are strong enough to be harmful. In fact, Eagleman​​ and Vaughn don't really discuss any direct evidence for the dreams-as-defense... (MORE - details)
Another problem is that some/many of my dreams aren't all that visual. As far as I can remember my dreams, many/some of them seem to be problem-solving dreams in which I'm struggling with some intellectual problem that might not make a whole lot of sense when I wake up.
My dreams are always very visual and are like movies with intricate plot details.

I wonder if cases of people being in darkness for long periods of time confirm damage to the optical cortex. Even in those cases though people are known to hallucinate visual images.
That's a silly theory. Since those who go blind later in life both continue to have visual dreams and spend all of their waking life in darkness, that alone would seem evidence against this theory. The visual cortex is still being activated, despite ~16 hours of darkness every day.

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