Name: 【TED-Ed】The neuroscience of imagination - Andrey Vyshedskiy
Uploaded: 2017-07-12T08:48:23.000Z
Duration: 4 min 49 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Imagine, for a second, a duck teaching a French class,

a ping-pong match in orbit  around a black hole,

You probably haven't actually seen any of these things,

How does your brain produce an image of something you've never seen?

but that's only because  we're so used to doing it.

It turns out that this is actually a complex problem

that requires sophisticated coordination inside your brain.

That's because to create  these new, weird images,

your brain takes familiar pieces  and assembles them in new ways,

like a collage made  from fragments of photos.

The brain has to juggle a sea of thousands of electrical signals

getting them all to their destination at precisely the right time.

thousands of neurons  in your posterior cortex fire.

These neurons encode various  characteristics of the object:

This synchronous firing strengthens the connections between that set of neurons,

linking them together into what's known as a neuronal ensemble,

In neuroscience, this is called the Hebbian principle,

neurons that fire together wire together.

the whole ensemble will light up, assembling a complete mental image.

Dolphins are encoded by a different neuronal ensemble.

is encoded by a neuronal ensemble  associated with it,

the neurons wired together by that synchronized firing.

But this principle doesn't explain the infinite number of objects

that we can conjure up in our imaginations without ever seeing them.

The neuronal ensemble for a dolphin balancing a pineapple doesn't exist.

One hypothesis,  called the Mental Synthesis Theory,

If the neuronal ensembles  for the dolphin and pineapple

we can perceive the two separate objects as a single image.

But something in your brain  has to coordinate that firing.

One plausible candidate  is the prefrontal cortex,

which is involved in  all complex cognitive functions.

Prefrontal cortex neurons are connected to the posterior cortex

by long, spindly cell extensions called neural fibers.

The mental synthesis theory proposes that like a puppeteer pulling the strings,

the prefrontal cortex neurons send electrical signals

to multiple ensembles in the posterior cortex.

If the neuronal ensembles are turned on at the same time,

you experience the composite image just as if you'd actually seen it.

This conscious purposeful synchronization

of different neuronal ensembles by the prefrontal cortex

signals would have to arrive at both neuronal ensembles at the same time.

are much farther away  from the prefrontal cortex than others.

If the signals travel down both fibers at the same rate,

You can't change the length  of the connections,

but your brain,  especially as it develops in childhood,

does have a way to change  the conduction velocity.

Neural fibers are wrapped in a fatty substance called myelin.

and speeds up the electrical signals  zipping down the nerve fiber.

Some neural fibers have  as many as 100 layers of myelin.

can conduct signals  100 times faster or more

Some scientists now think that this difference in myelination

could be the key  to uniform conduction time in the brain,

and consequently,  to our mental synthesis ability.

A lot of this myelination  happens in childhood,

our vibrant imaginations may have a lot to do with building up brains

can craft creative symphonies throughout our lives.