How our brain creates a useful version of reality...latest neuroscience

David Eagleman
U of Houston

The blogpost "Are our lives controlled by our unconscious brain?" showed how the brain runs our lives while we are blissfully unaware.  The excellent PBS series, "The Brain with David Eagleman", created by neuroscientist Dr. David Eagleman, uses the latest neuroscience to also explore how the brain constructs a useful "reality" in "What is Reality?".




Does the brain accurately create "reality"?

Shadow/square illusion

Many visual illusions, like the “shadow/square”,  show how the brain doesn’t portray reality "accurately", but instead creates a more "evolutionarily-useful" version.

Eagleman states “Our perception of reality has less to do with what is happening ‘out there’ (in the world) and more to do with what’s happening ‘in here’ (in the brain).     

Is it "reality" when it's backwards?

Making cupcakes backwards

In Alyssa Brewer’s research at the University of California - Irvine, volunteers wear goggles with two prisms which flip the sides of the brain processing the information though each eye.  So to reach what you "see" on the right, you must reach for it on the left, in a “mind mash” in which "reality" is now backwards.   

Alyssia Brewer
U of California - Irvine

As Eagleman observes, “Even though I am consciously trying to get it right, I can’t help but respond in a certain way.”  This is all new to Eagleman, but in only one week of wearing the goggles, a volunteer's brain adapted
significantly, even though it required many changes in the operation of several neural systems.

The volunteer can now make cupcakes and navigate a maze fairly well, while Prof. Eagleman broke out in a sweat, was dizzy, nauseated and had to take breaks.   

Is "reality" different if many senses are involved? 

As Eagleman notes, “Sometimes it’s easy to assume that there is a single spot in the brain that takes care of this or that function...but in fact the vast networks of the brain are so much more complex than that.”   

Brain city

“If you were to look out over a city and ask ‘where is the economy located?’ you would see that there is no single answer to that.  Instead the economy emerges as the interaction of all the elements.” 

Our reality is formed from the perceptions gathered by our sensory receptors, which are turned into electrical signals and transported along superhighways of neurons.

Regions w/in brain city

Some parts of “brain city” specialize in vision, others hearing, touch, etc.   In vision, there are regions specializing in colors, or edges, or motion.  Our perceptions of reality arise from the interactions between these senses.  

Do we see "reality" or just what we focus on?

Paul Yarbis tracked eye movements while subjects explored complex images using special glasses.  A well-known study used “The Unexpected Visitor” by Ilya Repin.  During the first few seconds of seeing the image, subjects were asked “What is going on in this painting?”

The Unexpected Visitor
Ilya Repin

Watching the eye movements, the brain first “models” the picture, and concludes that “the man in brown is the visitor”.

However, when asked how many children there were, subjects responded “two” when there were actually three.  When asked how many paintings there were, the answer was “two or three” when there were actually seven.   

The brain evolved an "adaptively" useful picture of reality, not a perfect one, and as quickly as possible.  Our ancestors survived by focusing on seeing lions quickly w/o counting the trees around the watering hole.  Those who didn't, aren't our ancestors.      

Do others see a different "reality"?

Eagleman studied 6,000 subjects with “synesthesia”, the phenomena of seeing a letter, number, word or name with a particular color.   Eaglesman chose synesthesia as it "is one of the few conditions in which it is clear that someone else’s reality is different from mine and it makes it obvious that how we perceive the world is not ‘one size fits all'”.

How Hannah sees her name 

When one synesthete, Hannah, sees her name, it is colored like a sunset.

Eagleman explains, “…inside the brain all sensory information is made from the same stuff – electrochemical signals.   Synesthesia is the result of ‘cross talk’ between sensory areas of the brain…even minute changes in brain wiring can lead to different realities."

"Some people perceive weekdays to have locations in space.  Some taste words.  Others see music…our experiences of reality can be quite different.” 

The brain has never seen the "real" world 

The brain lives in darkness

Although sights, smells, tastes, sounds and touch come in through our sense organs, our brain sits in darkness and silence, in total isolation.

It’s never seen the outside world – only electrochemical signals from sense organs that travel through neural networks to somehow approximate reality.

The brain makes it into the bark of a dog, the smell of a rose, or the smile of a friend by sifting through the streams of signals to find patterns from which it manufactures “reality” - the product of millions of years of evolution. 

How does "reality" change in a crisis?

Corliss's view approaching
the scene

During a traumatic experience, "reality" seems to slow down.  While filming (shown in this episode) a wingsuiting flight, Jeb Corliss misjudged his position and “impacted flat, solid granite at 120 miles per hour.”

Corliss after the crash

After the crash, as Eagleman narrates, “Six seconds elapsed between the moment that Jeb hit the rock and the moment he pulled his rip cord.  He broke his leg and both of his ankles in the fall.  From Jeb’s perspective, those six seconds seemed to last a long time.  What was happening in Jeb’s brain?”

To find out, Prof. Eagleman dropped folk from 150 feet in the air with a digital display with numbers changing faster than the brain can process.  If "reality"/time really did slow down, then the numbers would be visible - but they weren't. 

So why did Jeb recall that "the rescue took about 2 ½ hrs.  But at the time, it felt like weeks.”

Amygdala taking charge

Eagleman discovered that “in a critical situation, an area of the brain called the amygdala kicks into high gear and focuses the brain on the situation at hand…memories are laid down with far more detail than under normal circumstances...you have more information at your disposal to work out how to stay alive. “

However, when the extremely detailed record is later replayed at normal speed in "reality", the events appear to take much longer.   

This richly-textured world is all just an illusion.

As Eagleman concludes “What if I told you that this world around us, this richly-textured world is all just an illusion – what we feel, what matters to us, our beliefs and our hopes, everything we are, happens in here (the brain).”