Why do we desire? Psychologists and neuroscientists have been debating the function of dreams for generations, but there is however no acknowledged response.

Now, David M. Eagleman​​ and Don A. Vaughn​ have proposed a new idea. Their preprint posting, which has not yet been peer reviewed, is known as The Defensive Activation idea: Dreaming as a system to protect against takeover of the visible cortex.

To my head, it can be a really primary and artistic idea, but I’m not convinced by it.

Here is Eagleman​​ and Vaughn​’s idea in nutshell: The part of dreams is to make certain that the brain’s visible cortex is stimulated throughout snooze. Or else, if the visible procedure have been deprived of input all evening prolonged, the visible cortex’s function may possibly degrade.

We know that the visible cortex, in the brain’s occipital lobe, can start off to react to non-visible alerts if it is deprived of visible input. In blind people today, for instance, the occipital lobe strongly responds to touch. This rewiring or repurposing of beneath-used brain parts is a type of neuroplasticity.

Neuroplasticity is usually regarded as a fantastic detail. But Eagleman​​ and Vaughn place out that for the visible procedure, neuroplasticity could really pose a threat, mainly because eyesight — not like our other senses — is just not lively all the time.

If we are in a dark location, or it can be evening, we get little or no visible input. So — in idea — our visible cortex would be vulnerable to ‘takeover’ by other senses, each and every solitary evening. Dreams, on this see, are our brain’s way of defending the integrity of our visible procedure by preserving it lively.


As I explained, I like the ingenuity of this idea, but I never seriously acquire it. We know that dreams are affiliated with stimulation of the occipital cortex throughout a snooze phase known as REM snooze. So it can be accurate that dreams encourage the visible procedure. But I’m not convinced that this is the main goal of dreams.

For just one detail, Eagleman​​ and Vaughn’s idea only tends to make feeling if neuroplastic repurposing of the cortex transpires extremely speedily. For the visible cortex to require defending, destructive neuroplasticity would require to take place in the area of a couple hrs. The authors do talk about evidence that quick neuroplasticity can take place, but they never present any evidence that these quick changes are solid enough to be destructive.

In point, Eagleman​​ and Vaughn never seriously talk about any direct evidence for the dreams-as-defense.

They present a correlation among amount of REM snooze and the rate of improvement between primate species. Primates whose infants find out to walk a lot quicker and get to maturity a lot quicker, are inclined to have significantly less REM. (People, the slowest maturing primates, have the most REM.)

Primate development and REM sleep

Primate improvement and REM snooze, from Eagleman and Vaughn (2020)

The thought is that a lot quicker improvement means slower neuroplasticity, and slower neuroplasticity means significantly less require to secure the visible cortex from encroachment. This is extremely significantly circumstantial. The authors do cite some other oblique evidence, but admit that: “The existing speculation could be analyzed a lot more carefully with direct actions of cortical plasticity.”

I imagine this speculation could be analyzed really very easily. You’d choose a group of human volunteers and give them an fMRI scan, at baseline, to establish the extent of their visible cortex and how visually selective it is (i.e. how very well it responds only to visible input, not touch or other senses.)

Then, for 24 hrs, half of the volunteers would don a blindfold to generate visible deprivation. 50 {d11068cee6a5c14bc1230e191cd2ec553067ecb641ed9b4e647acef6cc316fdd} would have REM snooze disrupted that evening (selective REM disruption is probable). At the 24 hour place, they get a next fMRI scan.

Eagleman​​ and Vaughn’s idea would forecast that the eyesight-deprived people today would have significantly less visually selective visible cortex, and, crucially, that REM disruption would enhance this result. The authors recommend a very similar experiment.